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The anatomy of a failed offset
Abstract
Biodiversity offsetting is widely applied but its effectiveness is rarely assessed. We evaluated the effectiveness of a nest box program intended to offset clearing of hollow-bearing trees associated with a freeway upgrade in southern Australia. The offset targeted three threatened vertebrates: squirrel glider (Petaurus norfolcensis), brown treecreeper (Climacteris picumnus) and superb parrot (Polytelis swainsonii). Clearing led to the loss of 587 tree hollows and the offset was the placement of an equivalent number of nest boxes in nearby woodland (1:1 ratio). Of these, we monitored 324 nest boxes in six sample periods between 2010 and 2013, yielding 2485 individual checks of nest boxes.
... Some management interventions have met with varied success for woodland birds. These include the establishment of nest boxes such as in plantings where hollowbearing trees are rare (Lindenmayer et al. 2015) and where they have been deployed as an offset for removing large old paddock trees (Lindenmayer et al. 2017a). In these cases, nest boxes were often occupied by: (1) pest species such as the Common Starling, (2) animals that may compete for natural hollows with birds like the European Honeybee (Apis melifera) (Cunningham et al. 2022), and/ or (3) bird species that are already common in agricultural landscapes and for which targeted conservation efforts are not needed (like the Galah Eolophus roseicapilla and Eastern Rosella Platycercus eximius) (Lindenmayer et al. 2015(Lindenmayer et al. , 2017a. ...
... These include the establishment of nest boxes such as in plantings where hollowbearing trees are rare (Lindenmayer et al. 2015) and where they have been deployed as an offset for removing large old paddock trees (Lindenmayer et al. 2017a). In these cases, nest boxes were often occupied by: (1) pest species such as the Common Starling, (2) animals that may compete for natural hollows with birds like the European Honeybee (Apis melifera) (Cunningham et al. 2022), and/ or (3) bird species that are already common in agricultural landscapes and for which targeted conservation efforts are not needed (like the Galah Eolophus roseicapilla and Eastern Rosella Platycercus eximius) (Lindenmayer et al. 2015(Lindenmayer et al. , 2017a. In some cases, the limited effectiveness of the establishment of nest boxes as a form of management intervention may have been associated with poor quality installation, the use of boxes that were not fit for purpose for birds of conservation concern, or both (Lindenmayer et al. 2017a). ...
... In these cases, nest boxes were often occupied by: (1) pest species such as the Common Starling, (2) animals that may compete for natural hollows with birds like the European Honeybee (Apis melifera) (Cunningham et al. 2022), and/ or (3) bird species that are already common in agricultural landscapes and for which targeted conservation efforts are not needed (like the Galah Eolophus roseicapilla and Eastern Rosella Platycercus eximius) (Lindenmayer et al. 2015(Lindenmayer et al. , 2017a. In some cases, the limited effectiveness of the establishment of nest boxes as a form of management intervention may have been associated with poor quality installation, the use of boxes that were not fit for purpose for birds of conservation concern, or both (Lindenmayer et al. 2017a). ...
Australia’s temperate woodlands are among the most heavily modified biomes globally. I summarise some of the work on birds in south-eastern Australia that identifies drivers of bird biodiversity loss and the effectiveness of management interventions. I particularly focus on studies by the Sustainable Farms project at The Australian National University which show that: (1) Bird occurrence is associated with the amount of woody vegetation cover at site, farm and landscape scales. (2) Planting to increase woodland cover has greater relative positive effects on birds than grazing control. However, grazing of plantings has inherently negative impacts. (3) There are different broad structural types of woodland (old growth, regrowth and replantings) and each supports different bird assemblages. (4) The highest bird biodiversity occurs on farms which support all three woodland structural types, as well as other natural assets like paddock trees and fallen timber. (5) Long-term data show that while some woodland species are increasing, twice as many species are declining. Despite the body of information on woodland birds, substantial knowledge gaps remain. These include understanding of: (1) the role of fire in woodland bird dynamics and habitat suitability, and (2) demographic processes like bird breeding success and how it affects long-term site occupancy. Bird biodiversity in Australian agricultural landscapes formerly dominated by temperate woodlands will be best supported by: (1) ceasing land clearing, (2) greater woodland regeneration and woodland planting, (3) limiting livestock grazing, and (4) limiting the impacts of the Noisy Miner (Manorina melanocephala).
... Larsen et al., 2018;Persson et al., 2015), or on a specific natural habitat or species (e.g. Lindenmayer et al., 2017;Quigley and Harper, 2006). While these studies provide valuable information on how the mitigation hierarchy is used, the results are specific and difficult to generalize. ...
... These thresholds can be used as an estimation of the size of the projects studied and may suggest that this is typically greater than the size of the offset. Yet even offset ratios of 1:1 (1 ha destroyed requires 1 ha restored) are considered insufficient to reach no net loss (Lindenmayer et al., 2017;Moilanen and Kotiaho, 2018;Quétier et al., 2015). Higher ratios may thus be required (perhaps more than 1:100) to mitigate the potential uncertainties associated with the success of measures (Gardner et al., 2013;Lindenmayer et al., 2017). ...
... Yet even offset ratios of 1:1 (1 ha destroyed requires 1 ha restored) are considered insufficient to reach no net loss (Lindenmayer et al., 2017;Moilanen and Kotiaho, 2018;Quétier et al., 2015). Higher ratios may thus be required (perhaps more than 1:100) to mitigate the potential uncertainties associated with the success of measures (Gardner et al., 2013;Lindenmayer et al., 2017). If biodiversity offsets are smaller than the threshold necessary to trigger the EIA process and a ratio of 1:1 is insufficient to ensure offset success, no net loss is unreachable. ...
While the mitigation hierarchy, which is designed to achieve no net loss of biodiversity, is being adopted in many countries, comprehensive evidence of its effectiveness at a national scale is lacking. Only a few major development projects covering specific natural habitats or a limited geographical scale are used as illustrative cases. There is a critical need for nationwide, up-to-date datasets to assess the scope of the implementation of mitigation hierarchy. In this study, we used a national database consisting of 2588 development projects to assess how this policy is implemented in France. We found that the objective of no net loss is primarily targeted through reduction measures implemented during the construction phase of development projects or through compensation measures, and that both of these are mainly based on technical solutions rather than geographical or temporals solutions. When offsets are required, these tend to be dispersed over many small sites and are mainly implemented in agricultural and natural areas, including areas of high ecological interest (~50%). These results suggest that ecological and financial additionality to other environmental policies may not be achieved. The findings also highlight significant differences in the treatment of small and large development projects, reflecting that the extent of this policy is uneven. These results demonstrate the importance of the availability of national data in providing an overall vision of the implementation of the hierarchy. However, a precise definition of stakeholders' roles and responsibilities is imperative to ensure information is entered into the database effectively and to allow the long-term monitoring of the achievement of no net loss at a national scale.
... Examples of artificial refuges include the use of nest boxes to protect cavity-nesting petrels from predators in Portugal (Bolton et al., 2004), perforated drainage pipes mimicking natural burrows to mitigate the effects of agriculture on owls in North America (Keppers et al., 2008), and artificial stone cavities used as hibernacula for newts in Norway, substituting rocks and logs displaced by urbanisation (Dervo et al., 2018). Yet, despite their widespread implementation, the use of artificial refuges in conservation and restoration is still a highly imprecise science (Lindenmayer et al., 2017). Artificial refuges are often implemented ad hoc, with little understanding of how they perform at a fundamental ecological level (e.g. ...
... Artificial refuges are often implemented ad hoc, with little understanding of how they perform at a fundamental ecological level (e.g. thermal and structural properties) relative to the refuges they seek to replace (Lindenmayer et al., 2017), and less still regarding their capacity to sustain wildlife populations (Lovegrove, 1991;Mackintosh, 2016). ...
... See Table S4 for glossary of terms. alternative to 'lost' natural refuges (Lindenmayer et al., 2017). Likewise, some offset requirements may be simply to provide rehabilitated habitat (e.g. ...
Artificial refuges are human‐made structures that aim to create safe places for animals to breed, hibernate, or take shelter in lieu of natural refuges. Artificial refuges are used across the globe to mitigate the impacts of a variety of threats on wildlife, such as habitat loss and degradation. However, there is little understanding of the science underpinning artificial refuges, and what comprises best practice for artificial refuge design and implementation for wildlife conservation. We address this gap by undertaking a systematic review of the current state of artificial refuge research for the conservation of wildlife. We identified 224 studies of artificial refuges being implemented in the field to conserve wildlife species. The current literature on artificial refuges is dominated by studies of arboreal species, primarily birds and bats. Threatening processes addressed by artificial refuges were biological resource use (26%), invasive or problematic species (20%), and agriculture (15%), yet few studies examined artificial refuges specifically for threatened (Vulnerable, Endangered, or Critically Endangered) species (7%). Studies often reported the characteristics of artificial refuges (i.e. refuge size, construction materials; 87%) and surrounding vegetation (35%), but fewer studies measured the thermal properties of artificial refuges (18%), predator activity (17%), or food availability (3%). Almost all studies measured occupancy of the artificial refuges by target species (98%), and over half measured breeding activity (54%), whereas fewer included more detailed measures of fitness, such as breeding productivity (34%) or animal body condition (4%). Evaluating the benefits and impacts of artificial refuges requires sound experimental design, but only 39% of studies compared artificial refuges to experimental controls, and only 10% of studies used a before‐after‐control‐impact (BACI) design. As a consequence, few studies of artificial refuges can determine their overall effect on individuals or populations. We outline a series of key steps in the design, implementation, and monitoring of artificial refuges that are required to avoid perverse outcomes and maximise the chances of achieving conservation objectives. This review highlights a clear need for increased rigour in studies of artificial refuges if they are to play an important role in wildlife conservation.
... Despite the growth in its use, evidence of the approach preventing biodiversity loss and performing successfully is not available (e.g. Harper and Quigley, 2005;Lindenmayer et al., 2017). Several factors appear to prevent success, including the misuse of scientific information in offset design (Maron et al., 2015a), a lack of adaptive management and compliance monitoring (Brown and Veneman, 2001;Lindenmayer et al., 2017), and goal ambiguity . ...
... Harper and Quigley, 2005;Lindenmayer et al., 2017). Several factors appear to prevent success, including the misuse of scientific information in offset design (Maron et al., 2015a), a lack of adaptive management and compliance monitoring (Brown and Veneman, 2001;Lindenmayer et al., 2017), and goal ambiguity . ...
... Accordingly, the terms under which marine offsetting liabilities are being agreed are unknown. Whilst non-compliance and biodiversity offset failure is described within literature (Brown et al., 2014;Brown and Lant, 1999;Brownlie et al., 2017;Burgin, 2009;Gibbons et al., 2017;Kentula, 2000;Lindenmayer et al., 2017;May et al., 2017;Pickett et al., 2013;Salzman and Ruhl, 2000;Walker et al., 2009) there has been limited attention paid to the institutional relationships that have allowed or pushed this to occur . ...
Biodiversity offsetting with associated aims of no net loss of biodiversity (NNL) is an approach used to align economic development with conservation. Biodiversity offsetting may be more challenging in marine environments, with recent evidence suggesting that the current application of the approach in Australian marine environments rarely follows ‘best practice’ and is unlikely to be meeting stated policy aims. To understand how and why this deviation from best practice is taking place in marine systems, we analysed current practice in Australia through in-depth semi-structured interviews with 31 participants with professional experience in the development and implementation of associated policy. Thematic analysis of results indicated that, despite commitment to best practice in principle, practitioners recognised that operationalisation of marine biodiversity offsetting was inconsistent and unlikely to be meeting stated goals such as NNL. Participants described the central barrier to the adoption of best practice as the technical complexity of assessing and quantifying biodiversity losses and gains, and uncertainty in restoration in marine contexts. With offsetting described as an integral part of development consent for marine economic development, both these barriers and their navigation presents threats to users setting off a chain of accepted activity leading away from best practice. These threats were perceived to arise from low governmental capacity or prioritisation for environmental management, institutional needs for a social licence to operate, and overarching demands for economic growth. We conclude that marine biodiversity offsetting has come to be ambiguous in its practical definition, with a range of conflicting factors influencing its use and preventing the standardisation required to meet rigorous interpretations of best practice necessary to ensure biodiversity protection and NNL.
... Ali et al. 2018;Bidaud, Schreckenberg, and Jones 2018;Ghosh 2015;Mabon et al. 2018;Narain and Maron 2018) and economic (e.g. Githiru et al. 2015;Habib et al. 2013;Lindenmayer et al. 2017) aspects of biodiversity offsets in isolation. ...
... One key factor influencing the effectiveness of biodiversity offsets is adequate enforceability (Gibbons and Lindenmayer 2007), as poor compliance can result in offsets not meeting their intended outcomes and thus causing a loss of biodiversity (Lindenmayer et al. 2017;Moilanen et al. 2009;Norton 2009). In order to be effective, biodiversity offset projects should be legally enforceable and auditable (Lodhia, Martin, and Rice 2018;Norton 2009). ...
... A major concern is that the effectiveness of biodiversity offsets is rarely measured during and after implementation (Lindenmayer et al. 2017). Monitoring, reporting and auditing of offset activities are needed to ensure that biodiversity offsets are either meeting their intended outcomes, or to identify ongoing improvements (Koh, Hahn, and Ituarte-Lima 2014;Kujala et al. 2015;Maron et al. 2010;Maron et al. 2012;Maron et al. 2016). ...
Biodiversity offsets are a mechanism for allowing economic development to proceed while ensuring that this is not to the detriment of environmental and social values. In order to achieve this, biodiversity offsets need to include environmental, social and economic aspects in an equitable and effective way. Australian legislation and policy relating to biodiversity offsets was reviewed and rated according to the level of equity and effectiveness, in terms of transparency, measurability and enforceability, to achieve outcomes. In all jurisdictions, gaps were found in the transparency, measurability and enforceability of offset regulations. In particular, the Commonwealth, having the overarching responsibility for the protection of biodiversity, was found to be lacking in the ability to fill these gaps. These gaps could result in a loss of biodiversity and ecosystem function and services, as well as having economic repercussions for communities and developers. It also raises questions as to whether Australia is meeting its obligation as a signatory to the Convention on Biological Diversity and its ability to meet the corresponding Aichi Targets (and the subsequent Global Biodiversity Framework).
... Given that formation of tree hollows by natural processes can take decades to centuries (Gibbons, Lindenmayer, Barry, & Tanton, 2000;Mac Nally, Soderquist, & Tzaros, 2000), artificial hollows (e.g., timber or plywood nest boxes) are commonly used to provide temporary habitat resources for hollow-dependent wildlife (Lambrechts et al., 2010;Lindenmayer et al., 2017;Mering & Chambers, 2014). The effectiveness of nest boxes is dependent on their ability to provide microhabitats that approximate natural hollows (Lindenmayer et al., 2009). ...
... Effect sizes show effect of box attachment category (tree, picket) compared to natural hollows, accounting for the effects of key covariates. Error bars indicate the 95% confidence intervals around each estimate South Wales, Lindenmayer et al. (2017) reported Brown Treecreepers using only 0-0.6% of the marine plywood nest boxes that were specifically constructed for this species. Two other studies that used generic rectangular cuboid-shaped plywood boxes constructed for Superb Parrots reported no use by this species (Le Roux et al., 2016;Lindenmayer, Crane, Blanchard, Okada, & Montague-Drake, 2015). ...
... As such, artificial hollow microclimates that buffer against climate variation by providing occupants with higher relative humidity and a more stable thermal profile are likely to influence the ongoing viability of populations of hollow-dependent fauna. This will be critical for the diverse communities of hollow-using fauna endemic to the extensively cleared and degraded woodland ecosystems across south-eastern Australia (Bennett & Ford, 1997;Gibbons & Lindenmayer, 2002), where nest boxes are commonly installed to provide supplementary habitats (Lindenmayer et al., 2017;Macak, 2020); particularly because much of this region is characterized by a Mediterranean climate with large variation in weather conditions from day to day and across seasons . Protection of large old trees with existing hollows must remain a priority, but where artificial hollows are required (Griffiths et al., 2018;Griffiths, Semmens, Watson, & Jones, 2020), they should be designed to maximize wall thickness and be installed so that canopy cover and aspect combine to reduce solar exposure during summer, thereby ensuring target fauna have access to well-insulated supplementary habitats. ...
Artificial tree hollows (e.g., nest‐boxes) are commonly deployed to mitigate the loss of mature trees within human‐disturbed landscapes. Their effectiveness as a habitat resource, and thus conservation management tool, is strongly influenced by the suitability of internal microclimate conditions. In south‐eastern Australia, spout hollows are a nesting resource used by a diverse community of vertebrate species. We tested the suitability of a novel nest box design (spout boxes) that mimicked the physical characteristics of spout hollows. We monitored the occupancy (n = 193) and internal microclimate (n = 131) of natural hollows and spout boxes within a woodland where natural tree hollows were once abundant. Both natural hollows and spout boxes were occupied and used for breeding by birds and mammals. Natural hollows had consistently higher humidity, and thermal maxima and minima were buffered, when compared with spout boxes. These differences were largely explained by wall thickness. Spout boxes displayed even more extreme temperature variation and lower humidity when not shaded. While more extreme microclimate conditions did not prevent usage, tolerable thresholds for hollow‐dependent species may soon be exceeded under current climate change projections. Managers need to carefully consider nest box design and positioning to ensure the suitability of these supplementary resources for conservation purposes.
... Cet objectif théorique associé à la mise en place de politiques publiques de compensation ont conduit à une augmentation rapide du nombre des mesures compensatoires ces vingt dernières années (Madsen et al. 2010). Cependant, l'apport et l'efficacité réelle des mesures compensatoires pour la biodiversité sont fortement controversés (Maron et al. 2012;Curran et al. 2014;Maron et al. 2016;Lindenmayer et al. 2017;Gibbons et al. 2018;Devictor 2018). ...
... La durabilité des dispositifs a ainsi été évaluée à de rares occasions pour les nichoirs (Lindenmayer et al. 2009;Lindenmayer et al. 2017), les îlots artificiels (Keith & Skjei 1974) ou les bâtis (Gameiro et al. 2020). Le coût de fabrication, de mise en place et de maintenance des dispositifs fait également l'objet de plusieurs études (McKenney & Lindenmayer 1994;Spring et al. 2001;Bedolla-Guzman et al. 2016;Gameiro et al. 2020). ...
... Furthermore, nestboxes have a limited durability and require funds for regular maintenance or replacement (Lindenmayer et al. 2009;Lindenmayer et al. 2017), which might be both difficult to sustain in the long term. Furthermore, Schwartz et al. (2020) found that nestboxes are more attractive for rollers than natural cavities in Vallée des Baux. ...
Pour faire face aux changements rapides de l’environnement induits par l’Homme, de nombreuses politiques publiques de protection de la nature ont été mises en place. Parmi celles-ci, les mesures compensatoires conduisent à restaurer des habitats d’espèces, qui peuvent cependant créer des pièges écologiques. Ce risque est particulièrement grand pour les dispositifs artificiels, largement plébiscités, dont il est aujourd’hui crucial d’évaluer l’impact sur les populations. Dans cette thèse, à travers les exemples du Rollier d’Europe et des Laridés coloniaux nichant dans le Sud de la France, je montre que le test de l’hypothèse de piège écologique est bien adapté à l’évaluation des dispositifs artificiels, et est généralisable à d’autres contextes. L’étude de mécanismes de création des pièges permet également la formulation de recommandations. Je propose une démarche adaptative pour la conception, la mise en œuvre et l’évaluation des projets de restauration et de compensation écologique.
... Proponents for biodiversity offsets note that if correctly framed within the context of the mitigation hierarchy, offsetting is a tool with a specific purpose, for addressing residual impacts on biodiversity caused by economic development after avoidance, mitigation and remediation measures have occurred (IUCN 2016a). Data on global biodiversity offset implementation is building , and the understanding of the mechanisms that result in biodiversity offset failings continue to improve (Bull et al. 2013;Bull et al. 2014; Maron et al. 2016;Lindenmayer et al. 2017;Simmonds et al. 2019). Critically, without the approach, negative residual impacts to biodiversity from human developments would otherwise be unaddressed and left to accumulate -hailing the "death by one thousand cuts" debate (von Hase & ten . ...
... This requires developers to predict and prevent negative impacts to biodiversity prior to any development actions taking place (BBOP [Business and Biodiversity Offset Programme] 2012). The conservation benefits of avoiding impacts are likely to outweigh, taking more uncertain remediation and offsetting measures once the damage has occurred (Watson et al. 2016b;Lindenmayer et al. 2017). Actions that drive adherence to the first step of the mitigation hierarchy include; following environmental regulations designed to protect biodiversity (e.g., through national planning process and negotiations between stakeholders), giving clear guidance on critical biodiversity areas (e.g., Key Biodiversity Areas), and making political decisions to set aside areas of high societal value (e.g., World Heritage Sites). ...
... The theoretical and practical challenges of achieving NNL of biodiversity from development are increasingly well described and are widely reported (Table 2.2). For example, a nest box program in Australia intended to offset the clearing of hollow-bearing trees did not achieve the intended biodiversity outcomes for three threatened vertebrates reliant on the trees due to: 1) a failure to consider equivalency (the nest boxes failed to provide habitat for the target species), 2) incorrect use of multipliers (the 1:1 offset ratio did not account for the risk of offset failure), and 3) a lack of compliance and monitoring to evaluate the true effectiveness (Lindenmayer et al. 2017). As illustrated here, many of the issues with offsets result from poor operationalisation, monitoring and compliance, rather than inherent to the concept itself (Quétier et al. 2014). ...
The most widely applied decision-making process for balancing the trade-offs between conservation and development activities is the biodiversity mitigation process, implemented using environmental impact assessment supported by a conceptual ‘mitigation hierarchy’
framework. Yet to date, the exploration of the biodiversity mitigation process to the primary resource sectors has not been widely investigated as a subject of study in conservation. In this thesis, I explore mitigating impacts from fisheries on marine megafauna, linking system-wide approaches with individual-level incentives in a unified framework.
The majority of this thesis focusses on a case study of sea turtle captures and mortalities in a coastal fishing community in Peru. A linked, but separate case study explores the application of the framework to all human impact on biodiversity more broadly. I begin at the broadest scale, by exploring challenges and solutions for a global mitigation hierarchy for nature conservation that could enable tracking of progress towards an agreed overarching objective, based on net conservation outcomes. The global framework research precedes an exploration of the biodiversity mitigation process in the case study coastal fishing system.
Throughout the fishery case study, I draw on established decision-making processes to better understand the conservation issue at hand and to develop an understanding of what is necessary to empirically calculate net outcomes in data-poor fishing systems using the
proposed framework. The decision-making processes I employ include qualitative ecological risk assessment theory to assess the efficacy of current management systems, and a qualitative management strategy evaluation process to support consideration of trade-offs. I seek to further improve data gathering processes in data-poor fishing systems by applying the IDEA (“Investigate”, “Discuss”, “Estimate” and “Aggregate”) structured elicitation protocol to control for personal bias and heuristics when drawing on stakeholder knowledge. Finally, I
characterise the social network of fishing-related information-sharing between fishers to inform understanding of social influences on decision making using network null models.
As humanity seeks to deliver nature conservation alongside development, broader perspectives on human impacts, and how best to mitigate them are needed. This research contributes to an important and timely dialogue that seeks to shift emphasis away from piecemeal actions that prevent biodiversity loss, and instead adopt a strategic and proactive approach to restoring nature that links broad scale concepts to locally tailored solutions.
... ( • Thirty studies evaluated the effects on mammals of providing artificial dens or nest boxes on trees. Fourteen studies were in Australia 8,9,12,13,15,16,18,19,21,22,24,27,29,30 , nine were in the USA [1][2][3][4][5][6][7]14,25 , three were in the UK 10,11,28 , one was in each of Canada 17 , Lithuania 20 , South Africa 23 and Japan 26 . ...
... Twenty-seven studies, in Australia 8,9,12,13,15,16,18,19,21,22,24,27,29,30 , the USA 1,3-7,14,25 , the UK 11,28 , Canada 17 , South Africa 23 and Japan 26 found that artificial dens or nest boxes were used by a range of mammal species for roosting and breeding. ...
... A study in 2010-2013 in a eucalypt forest in New South Wales, Australia (30) found that nest boxes were used by a range of native and non-native mammal species. Yellow-footed antechinus Antechinus flavipes were found in 12-14% of nest boxes, common brushtail possum Trichosurus vulpecula in 11-13%, and common ringtail possum Pseudocheirus peregrinus in 3-7%. ...
... Hannis and Sullivan, 2012, Ives and Bekessy, 2015, Spash, 2015, Sullivan, 2013. Comparatively few empirical analyses of biodiversity offsetting exist and those that do primarily examine high income countries, especially the US wetland banking system and Australia's federal and state offset regulations, and they widely report failure to achieve no net loss (Bull et al., 2013a, Curran, 2014, Harper, 2005, Lindenmayer et al., 2017, Zu Ermgassen et al., 2019. Considering the majority of offset policies occur in middle-and low-income countries, there is, according to Gelcich et al. (2017, p. 187) a 'glaring geographical gap' ...
... Although there are increasing policies, standards and guidelines for biodiversity offsets, comparatively few empirical analyses exist and those that do primarily examine high income countries and they widely report failure to achieve no net loss (Bull et al., 2013b, Curran, 2014, Harper, 2005, Lindenmayer et al., 2017, Zu Ermgassen et al., 2019. Considering the majority of offset policies occur in middle-and low-income countries, there is, according to Gelcich et al. (2017) a 'glaring geographical gap' for research opportunities focused on these countries, including in Central and South ...
Environmental offsets aim to find a balance between economic growth and biodiversity conservation by compensating for the adverse environmental impacts of development. In Colombia, environmental offsets are being put forward as the engine for a new sustainable development model. Colombia is considered a pioneer in environmental policy in Latin America, has various environmental compensation instruments and is currently taking a lead in the region in biodiversity offsetting.
This research examines environmental offsetting in policy and practice in Colombia, tracing the evolution of offsetting policy since the 1970s and the drivers behind the latest biodiversity offset regulations. Crossing the landscapes of Colombia, from rural fincas in the Andes and the valley of the Magdalena Medio, to the offices of industry, government and NGOs, this thesis examines the subject of offsetting and the meanings of biodiversity from different angles, revealing the importance of biodiversity as a national asset, a symbol of identity and inseparable from cultural diversity.
Through the use of semi-structured interviews, policy analysis and a case study of the hydroelectric dam Hidrosogamoso and forest offsets implemented in Parque Nacional Natural Serranía de los Yariguíes, this research offers empirical evidence of the successes, multidimensional challenges, contradictory policies and contested practices associated with offsets. Drawing on political ecology and peace and conflict studies, centred on the themes of biodiversity and conflict, the research explores the conflicts that arise as a result of direct, systemic, and cultural violence towards people and nature, revealing parallels between a socio-ecological conflict at the impact site and the offset site. It draws attention to the threats facing human rights and environmental defenders amid historical patterns of colonisation and extractivism, land use conflicts and current post-conflict peacebuilding challenges.
This study examines the discursive constructions of biodiversity and highlights the social impacts of offset projects implemented in a protected area, as well as the practical and ethical challenges of attempting to offset environmental harm, challenging win-win and no net loss narratives promoted under green growth agendas. It argues that by creating a reliance on extractive development and transnational capital to carry out conservation, offsets are a double-edged sword that risk becoming a new tool of (neo)extractivism that is ultimately environmentally and socially unsustainable.
... 24,32 An offset can therefore meet all of its regulatory requirements and still fail to restore the biodiversity losses it was intended to compensate. 33 Consequently, rapid adoption of biodiversity offset policies has been met with equally rapid emergence of skepticism toward offsetting as an effective conservation mechanism. 18,28,34 Another key challenge in tracking the ecological impact of offsetting is the complexity of the offset policy landscape. ...
... 12,35,70,71 But even in countries with public registers, the information collected is generally not adequate or of the right type (Figure 2), or there might not exist infrastructure or capacity to collate, utilize, and oversee the collected data. 72 This highlights broader problems in offset governance where conditions of offset approvals do not necessarily require demonstration of offset effectiveness 19,24,33 or where there is a lack of clarity regarding who within the fragmented regulatory authority is responsible for monitoring compliance. 14,69,73 These issues are not specific to biodiversity offsetting; under-resourcing is a chronic and not apolitical problem in environmental law and policy, leading to regulatory decisions that deviate from original policy objectives (bureaucratic slippage) and ultimately shifting the power to control regulatory decisions to the regulated community (regulatory capture). ...
In the face of the ongoing biodiversity crisis, questions are arising regarding the success, or lack thereof, of biodiversity offset schemes, where biodiversity losses from human development are compensated by producing equitable gains elsewhere. The overarching goal of offsetting is to deliver no net loss (NNL) of biodiversity. Assessing whether offsetting does indeed deliver NNL is, however, challenging because of a lack of clear and reliable information about offset schemes. Here we consider barriers in tracking NNL outcomes, outline criteria of public offset registers to enable accessible and credible reporting of NNL, and show how existing registers fail to satisfy those criteria. The lack of accessibility and transparency in existing registers represents a fundamental gap between NNL targets and a valid tracking system, which challenges the impetus to enact the transformative changes needed to reverse biodiversity decline.
... Images by the authors. The repurposed structure image developed with Alex Holland and Anton Maksimenko at the Australian Synchrotron (Rueegger, 2017) Lifespan Variable: range from <4 years (Lindenmayer et al., 2017) to 10 years (Lindenmayer et al., 2009) and longer (Goldingay et al., 2018) Variable: dependent on age and weathering; long-term studies on attrition are needed (Griffiths et al., 2018) Variable: often short, sometimes <3 years (Carey & Sanderson, 1981;Terry et al., 2021) Microclimate conditions ...
... Variable: can support endangered species (e.g. Brazill-Boast et al., 2013) but can perform poorly (Lindenmayer et al., 2009(Lindenmayer et al., , 2017 and attract non-target species (Stojanovic et al., 2020) Moderate: can attract target species (e.g. mammals, Suckling & Goldstraw, 1989) Variable: can attract target species (Griffiths et al., 2020;Rueegger, 2017;Terry et al., 2021) but sometimes unsuccessful (e.g. ...
The decline of critical habitat structures, such as large old trees, is a global environmental challenge. The cavities that occur in these trees provide shelter and nesting sites for many species but can take centuries to develop. Artificial cavities, including nest boxes and carved logs, offer an increasingly important conservation response. However, current methods of designing, manufacturing and deploying such habitats have constraints that limit innovation, feasibility and effectiveness. In response, this article aims to provide new and broadly useable methods that can improve the design of habitat structures for cavity‐dependent animals. To address the shortcomings of existing methods, we develop an approach that uses computer‐aided design techniques of generative and parametric modelling to produce structures that satisfy stakeholder needs, computer‐aided manufacturing techniques of 3D printing and augmented‐reality assembly to build functional prototypes, and computer‐assisted techniques of laser scanning and data‐driven design to support installation, monitoring and iterative improvement of designs. We demonstrate this approach through a case‐study project that designs and instals habitat structures for the powerful owl Ninox strenua, a cavity‐dependent and threatened bird. Through a comparison with existing methods, our pilot study shows that computer‐aided design and manufacturing can provide novel and useful approaches to develop artificial habitat‐structures. Computer‐aided design finds geometries that approximate the complex characteristics of natural tree cavities and automatically produces new versions to suit diverse sites or species. Computer‐aided manufacturing integrates materials that match the performance of naturally occurring habitat structures and facilitates the assembly of complex geometries by non‐experts. Computer‐assisted techniques produce precisely fitting and easy‐to‐instal designs, which support gradual improvement through ongoing prototyping and evaluation. These capabilities highlight how advanced design techniques can improve aspects of artificial habitat‐structures through geometric innovation, novel construction techniques and iterative exploration. Significantly, computational approaches can result in designs that can perform well, are easy to construct and instal and are applicable in many situations. Our reusable workflow can aid in the tasks of practical conservation and support ecological research by effectively negotiating the needs of both humans and target species.
... Of Australia's native parrots, 12 species are endangered (Dooley and Vine 2013), among them the world's only migratory parrots, the Orange-bellied Parrot (Neophema chrysogaster) and the Swift Parrot (Lathamus discolor). While a variety of threats affect each of these 12 species, the impacts of habitat loss (and associated loss of breeding sites) and invasive species are significant threatening processes for many of these birds (Cameron 2006;Holdsworth 2006;Stojanovic et al. 2014bStojanovic et al. , 2016Le Roux et al. 2016a;Lindenmayer et al. 2017). ...
... For some species, nest boxes can supplement the lack of natural tree hollows (Tidemann et al. 1992;Heinsohn et al. 2003;Brazill-Boast et al. 2010;Webb et al. 2012;Goldingay et al. 2015). However, boxes that are accessible to invasive species or native predators may not be suitable for many native species (Lindenmayer et al. 2017), creating challenges for native cavity-nesting species conservation in urban areas. ...
... how close compensation comes to achieving NNL goals. While previous research has explored specific compensation policies and outcomes in certain locations 12,[17][18][19] , ours is the first to systematically examine a common set of policy settings across multiple case studies (Fig. 1), which vary in the local conditions that potentially influence policy performance (Table 1). We bring together the policy designs currently promoted globally 8,9 to examine 18 different options, representing combinations of two area-based approaches to generating biodiversity gains, four types of trades in biodiversity features between development and compensation sites, and three methods for prioritising compensation across the landscape (compensation policies often include a combination of these activities; Fig. 2). ...
... However, these reviews also reveal that when projects attempt to establish new habitat (as opposed to enhancing existing habitat), as is the case for compensation activities investigated in our study, and new habitats must resemble a similar condition to a reference site by a set time period, success rates are reduced even furtherso our assumption is generous. While there is currently a great lack of evidence of restoration success in the offsetting context 45 , recent studies suggest typically used multipliers are far from sufficient to overcome the risks of project failure 19,34 . Supplementary Figure 4 illustrates the effect of two alternative success rates (25% and 75%) on compensation impacts on biodiversity. ...
Many nations use ecological compensation policies to address negative impacts of development projects and achieve No Net Loss (NNL) of biodiversity and ecosystem services. Yet, failures are widely reported. We use spatial simulation models to quantify potential net impacts of alternative compensation policies on biodiversity (indicated by native vegetation) and two ecosystem services (carbon storage, sediment retention) across four case studies (in Australia, Brazil, Indonesia, Mozambique). No policy achieves NNL of biodiversity in any case study. Two factors limit their potential success: the land available for compensation (existing vegetation to protect or cleared land to restore), and expected counterfactual biodiversity losses (unregulated vegetation clearing). Compensation also fails to slow regional biodiversity declines because policies regulate only a subset of sectors, and expanding policy scope requires more land than is available for compensation activities. Avoidance of impacts remains essential in achieving NNL goals, particularly once opportunities for compensation are exhausted.
... Whether these new habitats function similarly to the destroyed habitat is uncertain. However, given the inherent unpredictability in ecological restoration and species responses, and previous research that suggests that attempts at no net loss have failed (e.g., Lindenmayer et al. 2017;Quétier et al. 2014;Quigley and Harper 2006), compensatory measures appear to be an ineffective strategy for minimizing impacts to biodiversity within EAs. To mitigate adverse ecological consequences, EAs must recognize the role that salmon play in maintaining the structure and function of ecosystems and ensure that projects do not contribute to the erosion of biocomplexity. ...
Mismatches between institutions and social–ecological systems (SESs) are one of the foremost challenges in natural resource management. However, while mismatches are often cited in the literature as a major challenge, empirical evidence of mismatches and their consequences is limited. This is particularly true for complex SESs, such as on the Pacific Coast of North America, where salmon drive interactions across multiple environments, jurisdictions, and scales. Here, I use the theoretical concept of fit to examine institutional alignment in a large-scale Pacific salmon SES, the Skeena River watershed in British Columbia, Canada. Utilizing Canadian federal environmental assessments as a proxy for colonial environmental governance institutions, I describe the common causes and consequences of mismatches between institutions and salmon SESs. This case study suggests that mismatches are threatening salmon sustainability and negatively affecting Indigenous People’s rights, livelihoods, and approaches to resource management and stewardship. I argue that improving social–ecological fit in salmon SESs will require new or revitalized forms of environmental governance that consciously fit the underlying social–ecological dynamics. While these findings are based on the Skeena River watershed, they may be generalizable to other salmon SESs in which mismatches between social and ecological processes and institutions exist.
... Widespread and ongoing loss of breeding habitat across the range of superb parrots (Manning, Lindenmayer, & Barry, 2004;Manning, Fischer, & Lindenmayer, 2006;Manning & Lindenmayer, 2009;Manning et al., 2013) is likely to exacerbate the effects of nest cavity scarcity we observed. Habitat restoration using generic artificial nest boxes for superb parrots have failed (Lindenmayer et al., 2017) and targeted solutions for other species increased interspecific competition (Stojanovic, Young, & Troy, 2019;Stojanovic et al., 2020a). Given uncertainty about the availability of nesting sites for superb parrots (Stojanovic et al., 2020c) and the challenges associated with artificial nests, protecting known suitable cavities is a logical first step toward relieving competition for superb parrots. ...
Reproductive skew occurs when a few individuals monopolize breeding output, which can act as a mechanism of natural selection. However, when population sizes become small, reproductive skew can depress effective population size and worsen inbreeding. Identifying the cause of reproductive skew is important for mitigating its effect on conservation of small populations. We hypothesized that superb parrots Polytelis swainsonii, which strongly select for the morphology of tree cavity nests, may be reproductively skewed toward pairs that monopolize access to nests. We use SNP genotyping to reconstruct a pedigree, estimate molecular relatedness and genetic diversity of wild superb parrot in the Australian Capital Territory. We successfully genotyped 181 nestlings (a census between 2015–2019) and showed they were the progeny of 34 monogamous breeding pairs. There was a strong reproductive skew – 21 pairs bred only once producing 40% of the nestlings, whereas 13 pairs bred two to four times, producing 60% of the total nestlings. Five of these repeat‐breeders produced 28% of all nestlings, which was nearly triple the productivity of one‐time breeders. Repeat breeders usually monopolized access to their nest cavities, but the few pairs that switched nests did not differ in fecundity from those that stayed. The cause of nest switching was unknown, but uninterrupted access to a suitable nest (not minor variations in morphology between nests) better predicted fitness of breeding superb parrots. Pedigrees offer powerful insights into demographic processes, and identifying reproductive skew early provides opportunities to proactively avoid irreversible loss of genetic diversity via conservation management. We identify new research questions based on our results to clarify the relationship between access to resources and breeding success. We reveal evidence of reproductive skew in a Vulnerable parrot. Reproductive skew erodes genetic diversity in small populations. We show that only a fraction of superb parrot pairs produced the majority of breeding output over five years. Breeders that monopolized access to rare nest sites were able to dominate reproductive output.
... This implies taking this phenomenon into account in the environmental impact assessment (EIA) of new highways. The EIA involves monitoring to evaluate the effectiveness of the impact avoidance and reduction measures implemented (Lindenmayer et al. 2017). However, this monitoring is based on the purpose of the mitigation measure. ...
Several studies assert that transportation infrastructure rights-of-way can play a positive role for many animal species, especially in highly fragmented and human-dominated landscapes. This study examines the contribution of highway stormwater ponds to amphibian ecological networks, questioning both the influence of their location on species richness and their capacity to increase landscape connectivity. The ecological networks of amphibian species were modeled by graph theory around highway A77 (France). Stormwater ponds as well as natural ponds were included as potential habitats and several connectivity metrics were calculated at different scales. The connectivity values of the stormwater ponds were analyzed in relation to species presence data collected in 2018. While most of these ponds contribute little to regional connectivity, some of them represent important connector patches. Statistical analysis also suggests that highway ponds are used by amphibians in areas with few natural pools. This raises questions about how to improve the management of ecological networks by considering the capacity of artificial habitats to serve as a refuge for biodiversity.
... Only a few studies to date have investigated whether breeding success in nestboxes is comparable to that in natural hollows, or the factors that influence nestbox usage (Sanz et al. 2003, Olah et al. 2014, Saunders et al. 2020. Nestboxes can also have problems; for example, they can be used by common or exotic species rather than the target species they were installed for, and usually require ongoing maintenance (Lindenmayer et al. 2017, Goldingay et al. 2018, Stojanovic et al. 2021. As nestboxes can be costly to instal and maintain, it is important to understand which factors increase the likelihood of use by the target species, and reduce the risk of occupancy by competitors (Goldingay & Stevens 2009, Lindenmayer et al. 2009). ...
Nestboxes have been deployed for parrots and cockatoos (Psittaciformes) worldwide, but there is limited evidence of their efficacy for these species. We examined the use of nestboxes by endangered South Australian Glossy Black Cockatoos Calyptorhynchus lathami halmaturinus, a habitat specialist that feeds almost solely on the seeds of drooping sheoak Allocasuarina verticillata trees, and investigated the factors that influenced nestbox use. Between 1998 and 2017, the mean annual proportion of nesting attempts that successfully fledged a chick was similar in nestboxes (52 %, n = 547) and natural hollows (53 %, n = 627). Nestbox use increased over time, which may reflect changes in the size and extent of the Glossy Black Cockatoo population over the study period. Nestboxes were more likely to be used by Glossy Black Cockatoos if they were close to the nest of another breeding pair and were not occupied by Yellow‐tailed Black Cockatoos Zanda funerea early in the breeding season. Nestboxes were also more likely to be used if they had been used in the previous breeding season, indicating nest‐site fidelity. The amount of A. verticillata feeding habitat in a 1km and 5km radius did not significantly influence nestbox use. Our study provides further evidence of the value of nestboxes to cockatoo conservation programs, but also suggests that multiple factors other than local food availability influence uptake by a target species. Given that Glossy Black Cockatoos prefer to aggregate their nests, nestboxes for this species are most likely to be beneficial when they are used to expand the capacity of existing breeding areas or are clustered in the landscape. Our study demonstrates that well designed nestbox deployments should consider the preferred social groupings of cockatoos during the breeding season, and the location of competitor species, in order to maximise nestbox uptake.
... One of the strategies commonly employed to recover populations of declining hollow-dependent fauna is to install artificial nest boxes 27 , but if these boxes are occupied by honey bees, then the strategy can be undermined. Honey bees have been reported as users of nest boxes in many landscapes [28][29][30] and in some cases are reported as among the most frequent users of these artificial structures 31,32 . ...
Feral Apis mellifera colonies are widespread globally and cause ecological impacts as pollinators and competitors for food and nesting opportunities. The magnitude of impact depends on their population density, but knowledge of this density is poor. We document feral A. mellifera colonies at 69 per km ² in fragmented Eucalyptus woodlands in Australia, exceeding estimates from elsewhere in the world, and matched only by one other Australian study. We surveyed 52.5 ha of woodland patches with 357 nest boxes installed to provide nesting opportunities for threatened vertebrates. Our sites covered a region of more than 140 km across with repeated surveys over 3 to 6 years. We show that nest box use by feral A. mellifera colonies is influenced by box design (p = 0.042), with weak evidence for an interactive effect of type of vegetation at a site (woodland remnants vs. replanting) and woody cover within 500 m (p = 0.091). At 69 colonies per km ² , this density is equivalent to the recommended stocking of hives for pollination of some crops and is therefore likely to influence pollination and lead to competition with other flower visitors. Apis mellifera is also likely to be competing for hollows with cavity dependent native fauna, especially in landscapes where there has been extensive tree removal.
... Acceptable offset implementation relies heavily on enforcement (IUCN 2014). Given our findings in this study that artificial nest hollows on average require servicing every 3-4 years, it would seem prudent for regulators that approve the use of artificial nest hollows as environmental offsets for Carnaby's cockatoos to also include a requirement that sufficient funds are set aside to cover the costs of monitoring and repair of those hollows (Lindenmayer et al. 2017). The monitoring serves two functions in that it provides important information to confirm that the artificial hollows are fulfilling their intended purpose (Richards et al. 2020), and it provides regular information on when and what type of repairs are required. ...
Loss of nest hollows in eucalypt woodlands is a major cause of decline for a range of Australian native birds including Carnaby’s cockatoo Calyptorhynchus latirostris. Loss of breeding habitat, plus decay of natural hollows, results in fewer nest sites for this species. Provision of artificial nesting hollows for Carnaby’s cockatoo is a recent part of approved environmental offsets under Western Australian and Australian government environment approvals processes. In this study we examined the continuing utility of natural and artificial nest hollows over time and show that both nest types require repairs on average every 3-4 years. Repairs extend the working life of natural nest hollows and ensure that any artificial nest hollows established for conservation management purposes should continue to fulfil their purpose. We provide data on the costs associated with the supply and deployment of artificial nest hollows, and indicative annual cost per nest hollow for repairs to natural and artificial nest hollows. Our results demonstrate the importance of regular maintenance to ensure hollows remain available for breeding cockatoos. Artificial nest hollows provide a short-term solution to a larger problem of loss of native woodlands, but will only serve that purpose if current and future artificial nest hollows are monitored and repaired on a regular basis, and that adequate funds are provided to ensure that those nest hollows remain serviceable. Provision and maintenance of large numbers of artificial hollows in association with restoration/replanting of woodlands in breeding areas is the only long-term solution to loss of breeding habitat.
... Notably, there is also the potential for the misuse of artificial habitat structures in the context of biodiversity offsets (eg Lindenmayer et al. 2017). Biodiversity offsets seek to compensate for the impacts of environmentally destructive actions by creating equivalent gains elsewhere (zu Ermgassen et al. 2019). ...
... Development offsets have faced a number of criticisms and problems, including that offsets have sometimes been used to meet a preexisting conservation commitment, which means that there is no new offset (Maron et al. 2015); the defined "counterfactual" (i.e., what would have happened at the offset site in the absence of the offset) has sometimes exaggerated the baseline rate of environmental losses (Sonter et al. 2017); those assessing the benefits provided by offsets have sometimes ignored the fact that it takes time to start delivering benefits following the establishment of new vegetation (Maron et al. 2016); and particular offsets have sometimes failed to deliver their expected environmental benefits (Lindenmayer et al. 2017;May, Hobbs, and Valentine 2017). This suggests that although development offsets have the potential to play a useful role in restoring and protecting habitat, they must be carefully designed and implemented and based on a clear understanding of the problems outlined here. ...
... Heatwaves are increasing in intensity and duration across the globe (Perkins-Kirkpatrick and Lewis 2020) and pose a threat to human populations (Nitschke et al. 2011) and wildlife (Ratnayake et al. 2019). In Australia, loss of tree hollows has led to the widespread use of nest boxes as a conservation tool (Lindenmayer et al. 2016(Lindenmayer et al. , 2017Macak 2020). However, high temperatures within nest boxes during summer heatwaves could render them unsuitable for use by target wildlife (Griffiths et al. 2017;Rowland et al. 2017). ...
In urban bushland, the installation of nest boxes is widely used to compensate for the loss of natural tree hollows. However, current nest box designs may not provide thermal refuges for wildlife during summer heatwaves, particularly if internal temperatures exceed the upper critical temperatures of wildlife. We investigated whether the addition of roofing insulation to nest boxes deployed for sugar gliders (Petaurus breviceps) and squirrel gliders (Petaurus norfolcensis) in urban bushland would reduce internal nest box temperatures during summer heatwaves. We measured temperatures of 44 insulated and 47 uninsulated nest boxes during one of the hottest summers on record (2018–2019) in the Lake Macquarie region of NSW, Australia, a period during which several prolonged heatwaves occurred. Over the 90-day study, maximum temperatures were, on average, 3.1°C lower in insulated boxes than in uninsulated boxes. The addition of insulation significantly lowered nest box temperatures regardless of aspect (north or south facing) or day of measurement. Temperatures exceeded the upper critical temperature (35.1°C) of gliders more frequently in uninsulated nest boxes (28% of days) than in insulated nest boxes (8% days). Although the addition of insulation to nest boxes lowered their internal temperatures, during heatwaves spanning 23 days, nest box temperatures exceeded the upper critical temperatures of gliders on 58% and 23% of days in uninsulated and insulated nest boxes respectively. These findings underscore the importance of retaining natural hollows in urban bushland to provide thermally suitable refuges for wildlife during extreme heat events.
... While artificial nest deployments for parrots are often successful (White et al. 2006;Tatayah et al. 2007;Saunders et al. 2020), this is not always the case. For example, artificial nests are sometimes occupied by nontarget species (Stojanovic et al. 2020(Stojanovic et al. , 2021a or are not occupied by the target species at all (Lindenmayer et al. 2017;Wimberger et al. 2018). Given the costs associated with the construction and deployment of these nests, designing them with the nesting requirements of the target species in mind is crucial to optimize the use of conservation resources (Stojanovic et al. 2017). ...
Animals that breed in cavities formed through decay or mechanical damage often face limitations to reproduction due to a shortage of nest sites. Artificial nests are commonly deployed to increase the short‐term availability of breeding sites for these species. Often this is an effective approach; however artificial nests are costly and may be ignored by the target species or inadvertently benefit non‐target species. Here we consider the use of modified natural hollows and artificial nest sites to support endangered Norfolk Island green parrots Cyanoramphus cookii. We recorded the characteristics of all modified and artificial nests in the Norfolk Island National Park and used eight years of nesting data to study nest selection by green parrots and introduced crimson rosellas Platycercus elegans. Artificial nests (those lacking a natural base) were never used by green parrots. Nests with thicker walls were more likely to be used by green parrots, but there was no nest site characteristic that predicted frequency of use. Crimson rosella nest use was not predicted by any of the nest characteristics measured. A better understanding of the reasons behind green parrots’ avoidance of artificial nests and preference for thicker nest walls is required to inform the future design and management of nest sites. Our study shows that evaluation of how artificial sites are used by the target species is important to maximize the efficacy of conservation efforts. This article is protected by copyright. All rights reserved.
... Notably, there is also the potential for the misuse of artificial habitat structures in the context of biodiversity offsets (eg Lindenmayer et al. 2017). Biodiversity offsets seek to compensate for the impacts of environmentally destructive actions by creating equivalent gains elsewhere (zu Ermgassen et al. 2019). ...
Habitat destruction and degradation, and their interaction with other threats, are driving animal declines worldwide. One approach increasingly proposed for mitigating these threats is to create artificial habitat structures as substitutes for destroyed natural structures. Here, we provide the first general definition of artificial habitat structures and synthesize important considerations for effective use. We show that they are a versatile conservation tool that have been trialed in a variety of contexts globally, to varying degrees of success. Their design must be well-informed by the drivers of natural habitat selection and their use should be part of an experimental framework to enable evaluation and refinement. We highlight possible ecological risks associated with their use and urge that artificial habitat structures are not used as inappropriate biodiversity offsets or for greenwashing. Looking forward, cross-disciplinary collaborations will help design sophisticated and effective structures to assist animal conservation in this era of rapid global change.
... Biodiversity offset schemes can intentionally or unintentionally set targets that reach some biodiversity baseline formulated by specific counterfactual statements but may not necessarily reach intended conservation progress (see Maron, Gordon, Mackey, Possingham, & Watson, 2015;Simmonds et al., 2019;Sonter et al., 2017). For example, the offset ratios may be inadequate if they fail to account for the risk of offset failure (for a quantitative example see Lindenmayer et al., 2017). This inconsistency when applying counterfactual thinking is particularly problematic when using matching methods, as the evaluator must decide which variables to include and which not. ...
... Ermgassen et al., 2019, there is also abundant evidence that they can fail to meet their objectives resulting in BES losses (e.g. Morris et al., 2006;Quigley and Harper, 2006;Ruhl and Salzman, 2006;Gibbons and Lindenmayer, 2007;Walker et al., 2009;Burgin, 2010;Hossler et al., 2011;Quétier and Lavorel, 2011;Suding, 2011;Maron et al., 2012;Gordon et al., 2015;Koh, Hahn and Ituarte-Lima, 2017;Lindenmayer et al. 2017;Moilanen and Kotiaho, 2018;Ermgassen et al., 2019;Griffiths et al., 2019). Similar problems can also occur in the rehabilitation/restoration stage of the mitigation hierarchy. ...
PROVISION OF TECHNICAL SUPPORT RELATED TO TARGET 2 OF THE EU BIODIVERSITY STRATEGY TO 2020 –MAINTAINING AND RESTORING ECOSYSTEMS AND THEIR SERVICES
ENV.B.2/SER/2016/0018
Guidance on achieving no net loss or net gain of biodiversity and ecosystem services
... The objective is therefore to reach a no net loss (NNL). Current practices of BO, whose effectiveness is rarely assessed, are harshly criticized on numerous counts (Bezombes et al., 2019;Bull and Strange, 2018;Curran et al., 2014;Gibbons et al., 2018;Lindenmayer et al., 2017;Maron et al., 2018;Moreno-Mateos et al., 2015;Weissgerber et al., 2019;zu Ermgassen et al., 2019). Despite important improvements, implementing BO remains a challenge (Gardner et al., 2013). ...
Ecological compensation is a principle according to which negative impacts on biodiversity should be compensated for. Biodiversity offsetting (BO) is the requirement to compensate quantified losses by quantified biodiversity gains considered to be equivalent. Compensation policies reducing ecological compensation to BO overlook the fact that the notion of biodiversity has both analytical and normative aspects. To substantiate this idea, we analyze the French case, which is one of the most developed ecological compensation policies in the world. We show that this policy is torn between two antagonistic trends. The first trend leads decision-makers and practitioners to embark on a numerical quest for “no net loss” of biodiversity. The second trend explores new organizational strategies consisting of a change in spatiotemporal scale and scope. This second trend challenges the precepts of BO and the associated objective of no net loss. We argue that the first trend reflects the analytical aspect of biodiversity but ignores the normative one, while the second trend does the exact opposite. A serious ecological compensation policy should reconcile both aspects to do justice to the complexity of biodiversity. We elaborate the organizational building blocks of such a two-tier ecological compensation policy, which is key to participate in stopping the erosion of biodiversity.
... Our findings also confirm previous studies showing that nest boxes poorly replicate the microclimate of tree cavities. Therefore, we highlight the need to focus on protecting cavity trees, while treating nest boxes as temporary solution in species conservation, whose significant installation and maintenance costs could be difficult to sustain in the long term (Goldingay et al., 2018;Lindenmayer et al., 2009Lindenmayer et al., , 2017. ...
Artificial devices are increasingly used in conservation measures to mitigate the disappearance of natural habitats. However, few studies have demonstrated their benefits for the target species, and they may pose a risk of creating ecological traps. This occurs when lower individual fitness is found in artificial habitats that are more attractive than their natural equivalents. In this study, we tested the ecological trap hypothesis on a dense population of European rollers Coracias garrulus breeding in both natural cavities and nest boxes. Our initial prediction was that the more stress-ful microclimatic conditions of nest boxes would lead to reduced fitness of European rollers, thus creating an ecological trap. The results showed that nest boxes were preferred over natural cavities. Despite significantly more extreme microclimatic conditions in nest boxes, we found similar breeding parameters between artificial and natural nest types. Our results also suggest that European rollers selected the nest boxes which best buffered the temperature, thus avoiding potential ecological traps. Overall our results led to the conclusion that nest boxes do not create ecological traps for European rollers in this study area. However, other species may be more sensitive to microclimatic variations or less able to avoid the least favorable nest boxes. These findings could help to inform the placement of nest boxes in order to reduce extreme temperatures and variation in humidity rates. Future studies could compare nest types for other fitness parameters, such as juvenile body condition or survival. We also recommend the ecological trap hypothesis as a useful framework to evaluate the outcomes of artificial devices used for conservation. K E Y W O R D S buffering capacity, Coracias garrulus, humidity, natural cavities, nest box, preference, temperature
... Although emphasized as a valuable conservation tool by many (e.g., Reid 2013; Santos et al. 2015;Levrel et al. 2017), biodiversity offsetting attracts criticism. Much of the criticism targets ecological, technical, or governance aspects of policy, such as substandard performance of some established offsetting practices (Kujala et al. 2015;Lindenmayer et al. 2017;May et al. 2017); difficulties involved in quantifying and comparing different ecological units (Walker et al. 2009;Reid 2013;Goncalves et al. 2015); and challenges associated with monitoring and evaluating offsetting schemes over time (Reid 2013;Santos et al. 2015;Schoukens & Cliquet 2016). However, the ethical issues involved, often underlying much of the criticism, have received much less attention. ...
Biodiversity offsetting is an increasingly applied tool aiming to compensate for environmental damage caused by exploitation projects. Critics, however, raise concerns over the purported effectiveness of offsetting and question the ethical underpinnings and implications of offsetting. But these ethical dimensions have largely been overlooked in research, which may lead to offsetting systems that fail to respect the values intended to be safeguarded. To address these dimensions five ethical objections in the scientific literature are identified: (1) offsetting violates nature's intrinsic value; (2) losses of nature cannot be compensated for by human interventions; (3) too little is known to make adequate trades; (4) offsetting impedes virtuous dispositions toward nature; and (5) offsetting has negative justice implications. These objections, and arguments against them, are described and analyzed using the ethical concepts of intrinsic and instrumental values, and anthropocentrism and non‐anthropocentrism, as well as deontological, consequentialist, and virtue‐ethical paradigms. Ten recommendations to policy‐makers and five questions to practitioners are offered to aid decision‐making on biodiversity offsetting. The recommendations concern both policy and legislation, for example on the need to clarify aims and how to use flexibilities and multipliers. The questions mainly focus on process‐related issues. Hopefully, these recommendations and questions will encourage further discussion of the ethics of biodiversity offsets, which ultimately may help to respect the values of biodiversity and human welfare at stake. Article impact statement: Five ethical objections should be considered in the design and implementation of biodiversity offsetting. This article is protected by copyright. All rights reserved
... Our findings also confirm previous studies showing that nest boxes poorly replicate the microclimate of tree cavities. Therefore, we highlight the need to focus on protecting cavity trees, while treating nest boxes as temporary solution in species conservation, whose significant installation and maintenance costs could be difficult to sustain in the long term (Goldingay et al., 2018;Lindenmayer et al., 2009Lindenmayer et al., , 2017. ...
Artificial devices are increasingly used in conservation measures to mitigate the disappearance of natural habitats. However, few studies have demonstrated their benefits for the target species, and they may pose a risk of creating ecological traps. This occurs when lower individual fitness is found in artificial habitats that are more attractive than their natural equivalents. In this study, we tested the ecological trap hypothesis on a dense population of European rollers Coracias garrulus breeding in both natural cavities and nest-boxes. Our initial hypothesis was that the more stressful microclimatic conditions of nest-boxes would lead to reduced fitness of rollers, thus creating an ecological trap. The results showed that nest-boxes were preferred over natural cavities. Despite significantly more extreme microclimatic conditions in nest-boxes, we found similar breeding parameters between artificial and natural nest types. Our results also suggest that rollers selected the nest-boxes which best buffered the temperature, thus avoiding potential ecological traps. Overall our results lead to the conclusion that nest-boxes do not create ecological traps for rollers in this study site. However, other species may be more sensitive to microclimatic variations or less able to avoid the least favourable nest-boxes. These findings could help to inform the placement of nest-boxes in order to reduce extreme temperatures and variation in humidity rates. Future studies could compare nest types for other fitness parameters, such as juvenile body condition or survival. We also recommend the ecological trap hypothesis as a useful framework to evaluate the outcomes of artificial devices used for conservation.
... Offsets seek to compensate for the environmental costs of human actions, such as mining or urban development, by creating equivalent environmental gains elsewhere (Miller et al., 2015). If artificial refuges do not closely replicate natural refuges, and are therefore not used by target species, they are likely to fail to offset ecological damage (Lindenmayer et al., 2017). ...
One technique used to combat the growing global species extinction crisis has been to create artificial refuges—human‐made replacements for natural refuges destroyed during habitat modification. However, there is limited knowledge of how closely artificial refuges replicate the natural refuges they seek to replace. Mining threatens many species worldwide through large‐scale habitat modification, and artificial refuges have been proposed as a method to offset the resulting habitat loss. Here, we examined the microclimatic, physical, and biotic characteristics of natural dens occupied by the northern quoll (Dasyurus hallucatus)—an endangered marsupial threatened by habitat loss—and compared these to (a) superficially similar unoccupied crevices, and (b) artificial dens created by mining companies for northern quolls. Northern quolls occupied natural dens that were cooler and deeper than unoccupied crevices, likely to avoid lethal air temperatures as well as predators. Artificial dens provided similar thermal properties to occupied dens, but lacked key characteristics in having shallower den cavities, less complex surrounding habitat, increased feral cat visitation, and less small mammal prey compared to occupied dens. This study highlights the need to consider multiple facets when constructing artificial refuges, in order to avoid perverse outcomes, such as inadequate shelter, increased predation, and food shortages.
Loss of hollow-bearing trees threatens many hollow-dependent wildlife. To mitigate this process, artificial chainsaw-carved hollows (CHs) are often created in dead trees, yet little is known about their thermal profiles. We measured temperatures inside 13 natural hollows (8 live and 5 dead trees) and 45 CHs (5 live and 40 dead trees) in the central west of NSW, Australia, over the course of 2 summers. Maximum temperatures and daily temperature ranges within natural hollows and artificial hollows were similar in 2017–2018. Hollow temperatures were lower in thicker-walled hollows than in thinner-walled hollows. During the January 2019 heatwave, temperatures inside CHs in dead trees exceeded 35 °C—4 °C higher than the upper limit of the thermal neutral zone of sugar gliders—for 6.2 consecutive days (range 0–9 days). CHs in dead trees provided little buffering from thermal extremes; when air temperatures peaked at 44.6 °C, CHs in dead trees were on average 2.4 °C cooler than ambient (range: 5.5 °C cooler to 1.0 °C hotter than ambient). These results show that CHs created in dead trees may not provide suitable thermal conditions for hollow-dependent marsupials during summer heatwaves. Retention of large live trees, coupled with revegetation, is crucial for conserving hollow-dependent fauna in agricultural landscapes.
Hollow‐dependent fauna are declining worldwide, due primarily to the widespread clearing of hollow‐bearing trees. Artificial cavities such as timber and plywood boxes are commonly used to increase hollow availability, yet there is increasing evidence that they are poor facsimiles of natural cavities, characterized by lower insulative properties and a shorter field life. We evaluated whether plastic materials could create a nest box with a stable thermal profile that more closely resembles the complex shapes and textures of natural tree hollows while containing fewer mechanical joins that represent potential failure points when installed. We developed three sets of prototype nest boxes comprising various combinations of plastic density (10%, 25% and 50%), insulation (single vs. double wall with or without sawdust between them), nesting chamber (with or without timber inserts) and bedding (with or without decomposed heartwood) and compared their thermal performance in a temperature‐controlled laboratory to compare internal temperature and relative humidity. We found double‐walled plastic nest box with an internal timber‐lined chamber was best able to buffer ambient temperature fluctuations, consistently recording internal temperatures of 6+°C below maximum ambient temperature, maintaining high levels of relative humidity (76%–92%) when furnished with decomposed timber heartwood. This design also performed better during a simulated hot day; internal temperatures exhibiting twice the lag time of single‐walled designs, noting that plastic density had little influence on internal conditions. While the recruitment and protection of hollow‐bearing trees must be a priority, this work shows significant potential in improving the design and functionality of artificial hollows that are critical to the conservation of hollow‐dependent species. We found double‐walled plastic nest box with an internal timber‐lined chamber was best able to buffer ambient temperature fluctuations, consistently recording internal temperatures of 6+°C below maximum ambient temperature, maintaining high levels of relative humidity (76%–92%) when furnished with decomposed timber heartwood. This design also performed better during a simulated hot day; internal temperatures exhibiting twice the lag time of single‐walled designs, noting that plastic density had little influence on internal conditions.
‘Biodiversity offsetting’ aims to address the residual negative environmental impacts of human development. It’s goal is to achieve No Net Loss (NNL), and preferably a Net Gain of biodiversity attributes between development and offset sites. Biodiversity offsetting suffers from a lack of ‘proof of concept’, as little work has been done to critically test the ecological efficacy of offsetting practices. Offsetting of stream ecological functions was investigated in Aotearoa New Zealand, via review of regulatory documentation for 76 offsets and field assessments of 14 offset sites. Field results indicated some functions, including fish passage connectivity, respond rapidly post-offset enhancement whilst others exhibit recovery lags (such as fish spawning habitat provision). However, most offsets were considered unlikely to achieve NNL due to failures in practice and process. Factors included inadequate consideration for restoration uncertainty, inappropriate monitoring conditions, insufficient data and inequivalent trade-offs. Key linkages between aquatic and terrestrial ecosystems, particularly regarding floodplain connectivity, were poorly considered in offset implementation. Thus, development may be occurring based on inadequate regulatory processes, and poorly evaluated ecological outcomes. These findings join a growing body of evidence which indicates that, in the context of a global biodiversity crisis, offsetting is not achieving its purpose of NNL.
The loss of hollow-bearing trees is a key threat for many hollow-dependent taxa. Nesting boxes have been widely used to offset tree hollow loss, but they have high rates of attrition, and, often, low rates of usage by target species. To counter these problems, chainsaw carved hollows (artificial cavities cut into trees) have become a popular alternative, yet little research has been published on their effectiveness. We examined the usage of 150 chainsaw carved hollows by cavity-dependent fauna in the central west of New South Wales using observations from traditional inspection methods and remote cameras. Between October 2017 and April 2019, we detected 21 species of vertebrates (two reptile, one amphibian, 10 bird, and eight mammal species) inside chainsaw carved hollows, but the number of species detected was dependent on the chosen monitoring method. We detected six species inside hollows during physical inspections, whereas remote cameras detected 21 species entering hollows. Cameras detected eight species using hollows as breeding sites, whereas physical inspections detected just four species. Cameras detected two threatened mammals (squirrel glider (Petaurus norfolcensis) and greater glider (Petauroides volans)) raising young inside hollows, yet we failed to detect these species during physical inspections. For birds, the two methods yielded equivalent results for detection of breeding events. Overall, our study showed that few cavity-dependent species used chainsaw carved hollows as breeding sites. This highlights how artificial hollows are not a substitute for retaining naturally occurring hollows in large trees and revegetation programs.
The creation of mechanically carved tree cavities to provide supplementary shelter for hollow-dependent wildlife is increasingly popular in conservation management programs. However, there is limited empirical evidence quantifying how the features of their design and broader placement within the landscape influence use by target fauna. In this study, we took a multi-scale approach to investigating the use of chainsaw hollows (CHs) by a target native arboreal marsupial, Krefft’s Glider Petaurus notatus. We hypothesized that Krefft’s Gliders would respond to attributes of: (1) the CH itself; (2) the tree into which it was installed; and (3) the habitat within the reserve in which it was located. We monitored occupancy (over 2.7 years, using a pole camera) of 48 CHs installed in live Eucalyptus trees across multiple reserves in Melbourne, Australia, plus visitation (over ∼3 months, using camera traps) to 40 of the CHs. Mixed models were used to relate the occupancy of CHs by Krefft’s Gliders to field-collected data on various attributes of CHs at all three scales. From a total of 35,219 visitations across the 40 CHs, we recorded 13 native hollow-dependent species (five mammals, eight birds) visiting CHs. During 14 pole-camera inspections, Krefft’s Glider occupied 60% of the 48 CHs at least once, with 4% used as maternal dens during breeding. Four exotic species were also recorded visiting and/or occupying CHs. Orientation and volume both significantly affected occupancy: Krefft’s Gliders were more likely to occupy larger CHs, and those facing north and west (possibly related to microclimate). Tree-scale attributes did not affect occupancy, but Krefft’s Gliders were more likely to occupy CHs further from reserve edges, and where local density of Black Wattles (Acacia mearnsii: an important food resource) and low vegetation cover (100–200 cm above ground) was increased. Our findings show that CHs can provide supplementary shelters for Krefft’s Gliders when natural hollows are limited. Practitioners should consider both the physical characteristics of the cavity (e.g. volume) and the surrounding habitat (e.g. availability of foraging resources) to enhance the use of CHs by target species. The ongoing availability of CHs to target species will also be influenced by their use by exotic species, and potential for closure as woundwood grows. In an Australian context, a lack of knowledge about the specific features of natural hollows to which hollow-dependent fauna respond, means it is critical for policy and management to prioritize the retention of mature hollow-bearing trees.
Forest and woodland areas that have suffered historic degradation of habitat are likely to have reduced populations of tree-hollow dependent wildlife. We investigated the frequency of use of small-entry nest boxes installed 3 m high and vertical nest logs installed 1–3 m high, over 10–30 years in box–ironbark forest in north-east Victoria. Mammals were the dominant users of the nest boxes. Squirrel gliders and sugar gliders collectively used >75% of boxes and brush-tailed phascogales used >30% of boxes. Birds used the nest boxes on just two occasions. Brown treecreepers were the dominant users of the nest logs, with 48 breeding events across 30% of 105 nest logs. Turquoise parrots bred in the logs on five occasions. Gliders used 31% and phascogales 16% of the nest logs. These mammals were directly observed more frequently in the nest boxes than in the nest logs. Our findings show that mammals and birds preferred morphologically different hollows. Further research into the influence of different artificial hollow design elements is required. Nest boxes and nest logs required infrequent maintenance that was easily sustained over time. Our results suggest that tree-hollow dependent wildlife can benefit from restoration of their breeding and shelter sites.
Worldwide deterioration in natural communities has led to an increased use of fauna translocations to improve conservation status and restore ecological function. However, few translocation programs have sufficient resources to involve multiple species and destination locations with appropriate threat management and monitoring before and after release. As part of conservation actions to mitigate impacts of the Chevron Australia Gorgon liquefied natural gas project on Barrow Island Nature Reserve, biodiversity offset funding was provided to benefit species impacted by the development. Animals were translocated from three islands to two mainland locations in Western Australia. We aimed to: (1) improve conservation status and security of several threatened species; and (2) contribute to reconstruction of pre-European fauna assemblages. Nine hundred and seventy five individuals of six mammal and two bird species were translocated. These included 421 golden bandicoots (Isoodon auratus barrowensis), 111 spectacled hare-wallabies (Lagorchestes conspicillatus conspicillatus), 105 Barrow Island boodies (Bettongia lesueur ssp. Barrow Island), 104 brushtail possums (Trichosurus vulpecula hypoleucus), 62 mala (Lagorchestes hirsutus ssp. Tanami), 88 djoongari (Pseudomys fieldi), 37 black and white fairy-wrens (Malurus leucopterus edouardi) and 47 spinifexbirds (Eremiornis carteri). Of 11 new populations, only two failed to establish; attributed to native and feral predators. Additional populations of four species of threatened mammal (one of which has now been reduced in conservation listing) and one species of threatened bird were established. To our knowledge, this is the largest translocation effort ever undertaken in Australia and is a rare example of an offset that has provided tangible threatened species benefit.
Australia’s biodiversity is declining despite two decades of protection for threatened species under the nation’s key environmental legislation, the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). Among its main functions, the EPBC Act frames the assessment and approval of new developments. However, little research has been conducted into compliance with policy guidelines under the EPBC Act that outline minimum assessment requirements where projects potentially impact threatened species. Focusing on the Endangered northern quoll (Dasyurus hallucatus), we analysed ‘referrals’ (a required preliminary impact (self-)assessment) of proposed projects in the species’ range between 2007–2010 and 2016 onwards (i.e. before and after species-specific assessment guidelines released), to determine (1) the level of compliance with Commonwealth assessment guidelines, and (2) consistency in the type and amount of survey effort between the two time periods. Of the 33 referrals submitted after 2016 that we examined, only six conducted the minimum ‘reconnaissance survey’ requirement comprising a multi-faceted field data collection protocol. The types of surveys conducted also differed, albeit marginally, among referrals submitted between the two periods. Despite our findings of variation in survey approach (both periods), and the overwhelming failure to comply with minimum survey requirements (post-2016 only), all the projects we examined were approved under the EPBC Act without the need for further assessment. We suggest that assessments for threatened species under environmental legislation – including proposed national environmental standards in Australia – be improved through strictly enforced minimum survey requirements, lest inadequate environmental impact assessments jeopardise the recovery of threatened species.
Bat boxes are commonly deployed to mitigate the loss of bat roosting habitat. Due to a dearth of microclimate research, numerous untested commercially available bat boxes, and the uncertain impacts of a rapidly changing climate, the overheating risk presented to bats by bat boxes is largely unquantified. Based on limited research, we know many boxes overheat (i.e., temperatures >40°C). A lack of standardized protocols to evaluate microclimate and misleading information available to the public leads to a murky understanding of risks involved with deploying bat boxes. Herein, we evaluate the thermal tolerance of temperate‐zone bats, delineate areas of concern regarding the risks to temperate‐zone bats when bat boxes are deployed, identify strategies for reducing overheating risk, suggest methods for assessing microclimate, and provide a visual framework to assess overheating risk. Identifying suitable design and placement combinations is crucial to developing region‐specific strategies to mitigate against overheating. We urge consideration of the risks involved with using bat boxes, advocate for rigorous testing before deployment, and suggest using alternatives when possible.
Biodiversity offsetting is often presented as a way to manage competing demands of environmental protection and economic development. It is premised on the transparent demonstration of how aims of no net loss of biodiversity (NNL) or similar are met in practice. This is complicated in marine systems where ecological predictions are commonly highly uncertain, knowledge of ecological restoration is low and administrative governance is complex. Drawing on a case study of marine biodiversity offsetting in Australia, this paper shows how these uncertainties pose practical challenges for both producers and consumers of marine biodiversity offsets, needing to progress with decision-making while meeting increasing societal pressure for demonstrable NNL. These competing needs are met through the centrality of an auditable decision-making process that contributes to establishing an organisation’s social licence to operate. The need for auditability drives the use of an imprecise measure of NNL through financial equivalency and the use of strategic offsetting projects. The coarse-grained interpretation of biodiversity offsetting best practice reduces the risks posed by explicit acknowledgement of biodiversity loss, offset failure or prohibitively large offset liabilities. Strategic relationship management across government, industry, academia and non-governmental organisations has raised the profile of biodiversity and its importance, but whether the auditing process has delivered on environmental protection is an open question. What is ‘good enough’ to meet governance standards may have become the over-riding goal. We conclude by acknowledging that the seemingly unattainable yet expected aim of NNL for marine systems prioritises auditability above discussions of ‘acceptable’ risk.
Nest boxes are widely used for habitat restoration. Unfortunately, competitors of the target species may exploit nest boxes, creating perverse outcomes. Avoiding habitats preferred by non‐target species, while favoring those of the target species, requires an adaptive management approach if limited information about species preferences is available when deploying boxes. Using nest boxes intended for swift parrots Lathamus discolor, we identify factors associated with non‐target species occupancy (Common starling Sturnus vulgaris and tree martin Petrochelidon nigricans) in newly deployed boxes in 2016, and then again after three years had elapsed in 2019. Box occupancy by different species depended on the interaction between distance of individual boxes to the forest edge and year. Although the target species exploited similar numbers of nest boxes in both years, competitors were the main beneficiaries of established boxes. A subordinate, native nest competitor increased box occupancy likelihood at greater distances from forest edges in both years, but the relationship was stronger in 2019. Introduced common starlings Sturnus vulgaris were most likely to occupy boxes close to forest edges, but the magnitude of this relationship was much greater for established than newly deployed boxes. We suggest that permanent box deployments for swift parrots may produce perverse outcomes by increasing nesting habitat for common starlings. We suggest that for species that only use cavities for part of their life cycle, managers should limit access to boxes outside of critical times to reduce the likelihood that pest populations can exploit restoration efforts and create new problems.
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1.Interaction networks among native and invasive species in a community can inform both invasion impacts and applied management of invasive species. The intensity of aggressive interactions may be related to the overlap in species’ ecological niche and functional traits, especially in cavity‐breeding species, who must compete for limited nesting sites. Australia is home to over 100 native and introduced species, including several invasive species that are widespread globally, such as the common myna (Acridotheres tristis). Here, we aimed to test the extent to which shared functional traits inform the intensity of aggression between cavity nesting birds. 2.We quantified the outcomes of aggressive interactions between birds in large hollow‐bearing trees in SE Queensland, Australia. We examined whether more similarly sized birds interacted more frequently, whether larger species won aggressive interactions more often, and whether cavity‐breeding species with similar preferences for nesting sites (breeding niche space) interacted more frequently. 3.We recorded a total of 410 aggressive interactions and 48 interacting bird species around tree hollows, including 20 cavity‐nesting bird species. These interactions were dominated by the invasive common myna, the native noisy miner (a non‐cavity‐breeder), and the native rainbow lorikeet (Trichoglossus moluccanus), but the common myna won the largest total number of interspecific interactions. On average larger birds won aggressive interactions more frequently, yet there were some important exceptions to this finding; the common myna (113 ± 30 g) won 26 of the 29 interactions against the larger native rainbow lorikeet (126 ± 44 g). Importantly species with more similar nest‐site preferences were observed aggressively interacting more frequently. 4.Synthesis and applications. The impact of the invasive common myna was larger on species that are closer to the myna in body size and share nest site preferences. Control efforts for the myna should focus on birds that nest in natural tree hollows. An analysis of shared traits by managers could be used to help identify how many local species would benefit from common myna control in a given area and test if further behavioural studies of common myna are warranted.
Biodiversity offsetting is the practice of using conservation actions such as habitat restoration, management or protection to compensate for ecological losses caused by development activity, including construction projects. The typical goal of offsetting is no net loss (NNL), which means that all ecological losses are compensated for by commensurate offset gains. The focus of this work is a conceptual and methodological exploration of net positive impact (NPI), an ambitious goal that implies commitment to beyond NNL, and which has recently received increasing attention from both big business and environmental NGOs. We build upon three ways to deliver NPI: (i) use of an additional NPI multiplier, (ii) using permanent offsets to deliver additional gains after NNL has first been reached during a shorter offset evaluation time interval, and a (iii) novel modification of the mitigation hierarchy so that gains from its traditional third step, onsite rehabilitation, can no longer be counted towards reduced offset requirements. The outcome from these three factors is that for the same ecological damage, larger offsets will be required than before, and earlier, thereby necessarily improving the success expected from offsets. As a corollary, we show how offsets really are NNL only at one ephemeral point in time, before which they are net negative and after which they turn into either net positive impact or net negative impact, depending on whether permanent offsets are combined with partially temporary losses or if temporary offset gains are combined with partially permanent losses. While we provide operational guidance on how to achieve NPI, it should be understood that achieving it is fully conditional on prior achievement of NNL, and offsets have indeed been frequently observed to fail due to inadequate policy requirements, incompetent planning or incomplete implementation. Nevertheless, achieving NPI becomes straightforward if NNL can be credibly reached first. Article impact statement: Achieving a net positive impact of biodiversity offsetting is straightforward if no net loss can be credibly reached first. This article is protected by copyright. All rights reserved
Nest boxes have grown in popularity as a habitat management tool in Australia during the last decade. This management use remains contentious because some studies suggest nest boxes are ineffective. There are three recent contentions: (i) nest boxes mostly benefit common species, (ii) exotic species may be dominant users of nest boxes, and (iii) species of conservation concern use nest boxes infrequently. We address these contentions using data from 1865 nest boxes involving eight nest box designs. These nest boxes were installed predominantly <200 m from a road in association with highway duplication and re‐alignment across 16 projects in New South Wales. The Common Brushtail Possum (Trichosurus vulpecula) is the species of most relevance to contention 1. It used 9% of boxes overall including 26% of ‘possum’ designated boxes. The most frequent nest box users were small petaurid gliders (mostly Sugar Gliders, Petaurus breviceps) which used 63% of ‘small glider’ designated boxes. This nest box and another suited to the Sugar Glider comprised 40% of all boxes installed, so it is not surprising that this species might be a common user. Exotic species were uncommon users of the nest boxes enabling contention 2 to be rejected. Active hives of Feral Honeybees (Apis mellifera) occupied just 1% of boxes, and another 1% of boxes were used by introduced rodents and birds. The Squirrel Glider (Petaurus norfolcensis) is the species most relevant to contention 3. It was seen in 80 boxes across 11 projects, representing 7% of the three types most frequently used. These observations are not consistent with the third contention. Nest boxes can provide many important insights about the requirements and interactions of hollow‐dependent fauna. However, they are not intended as an alternative to retaining hollow‐bearing trees.
Nest boxes are often used to provide supplementary roosts for cavity-dependent wildlife, but little is known about if they influence faunal community composition. Long-term monitoring of bat boxes in south-eastern Australia indicated that their use was dominated by one generalist species (Chalinolobus gouldii), causing concern that installing bat boxes could cause a shift toward less diverse bat communities. To test this, we conducted a large-scale before-after control-impact experiment at 18 sites, over five years. Sites were either: (1) those with existing bat boxes, (2) those where boxes were added during the study, or (3) controls without boxes. We used echolocation call data from 9035 bat detector nights to compare community composition, diversity, and species’ relative activity between the sites. Chalinolobus gouldii continued to dominate the use of existing boxes, but we found little difference in community composition between sites based on the presence, absence, or addition of boxes. Our study is the first to explore the influence installing artificial hollows has on localized faunal assemblages over spatio-temporal scales relevant to management. We conclude that there is cause for optimism that bat boxes might not have perverse outcomes on local community composition in the short- to medium-term, as we had feared.
Large old trees are some of the most iconic biota on earth and are integral parts of many terrestrial ecosystems including those in tropical, temperate and boreal forests, deserts, savannas, agro-ecological areas, and urban environments. In this review, we provide new insights into the ecology, function, evolution and management of large old trees through broad cross-disciplinary perspectives from literatures in plant physiology, growth and development, evolution, habitat value for fauna and flora, and conservation management. Our review reveals that the diameter, height and longevity of large old trees varies greatly on an inter-specific basis, thereby creating serious challenges in defining large old trees and demanding an ecosystem- and species-specific definition that will only rarely be readily transferable to other species or ecosystems. Such variation is also manifested by marked inter-specific differences in the key attributes of large old trees (beyond diameter and height) such as the extent of buttressing, canopy architecture, the extent of bark micro-environments and the prevalence of cavities. We found that large old trees play an extraordinary range of critical ecological roles including in hydrological regimes, nutrient cycles and numerous ecosystem processes. Large old trees strongly influence the spatial and temporal distribution and abundance of individuals of the same species and populations of numerous other plant and animal species. We suggest many key characteristics of large old trees such as extreme height, prolonged lifespans, and the presence of cavities - which confer competitive and evolutionary advantages in undisturbed environments - can render such trees highly susceptible to a range of human influences. Large old trees are vulnerable to threats ranging from droughts, fire, pests and pathogens, to logging, land clearing, landscape fragmentation and climate change. Tackling such diverse threats is challenging because they often interact and manifest in different ways in different ecosystems, demanding targeted species- or ecosystem-specific responses. We argue that novel management actions will often be required to protect existing large old trees and ensure the recruitment of new cohorts of such trees. For example, fine-scale tree-level conservation such as buffering individual stems will be required in many environments such as in agricultural areas and urban environments. Landscape-level approaches like protecting places where large old trees are most likely to occur will be needed. However, this brings challenges associated with likely changes in tree distributions associated with climate change, because long-lived trees may presently exist in places unsuitable for the development of new cohorts of the same species. Appropriate future environmental domains for a species could exist in new locations where it has never previously occurred. The future distribution and persistence of large old trees may require controversial responses including assisted migration via seed or seedling establishment in new locales. However, the effectiveness of such approaches may be limited where key ecological features of large old trees (such as cavity presence) depend on other species such as termites, fungi and bacteria. Unless other species with similar ecological roles are present to fulfil these functions, these taxa might need to be moved concurrently with the target tree species.
The long-term effectiveness of restored areas for biodiversity is poorly known for the majority of restored ecosystems worldwide. We quantified temporal changes in bird occurrence in restoration plantings of different ages and geometries, and compared observed patterns with a reference dataset from woodland remnants on the same farms as our plantings. Over time, bird species richness remained unchanged in spring but exhibited modest increases in winter. We found that wider plantings supported significantly greater bird species richness in spring and winter than narrow plantings. There was no evidence of a significant interaction between planting width and time. We recorded major temporal changes in the occurrence of a range of individual species that indicated a clear turnover of species as plantings matured. Our results further revealed marked differences in individual species occurrence between plantings and woodland remnants. Life-history attributes associated with temporal changes in the bird assemblage were most apparent in winter survey data, and included diet, foraging and nesting patterns, movement behaviour (e.g. migratory vs. dispersive), and body size. Differences in bird assemblages between plantings of different ages suggest that it is important that farms support a range of age classes of planted woodland, if the aim is to maximize the number of native bird species in restored areas. Our data also suggest that changes in the bird species occupying plantings of different ages can be anticipated in a broadly predictable way based on planting geometry (especially width) and key life-history attributes, particularly movement patterns and habitat and diet specialisation.
Biodiversity offsetting is transforming conservation practice around the world. Development activities that degrade or destroy biodiversity at one location are now increasingly acceptable because of compensatory environmental gains generated elsewhere. This change represents a major shift in how nature is protected, and yet its philosophical justification has received little attention. We argue that biodiversity offsetting aligns most easily with a utilitarian ethic, where outcomes rather than actions are the focus. However, offsetting schemes often neglect to account for the multiple values that people assign to biodiversity including unique, place-based values. Furthermore, the implications of defining nature as a tradeable commodity may affect our sense of obligation to protect biodiversity. Ironically, offsetting may exacerbate environmental harm because it erodes ethical barriers based on moral objections to the destruction of biodiversity. By failing to consider the ethical implications of biodiversity offsetting, we risk compromising the underlying motivations for protecting nature.
Offsetting is a policy instrument intended to provide flexibility for development. We developed a simple calculator to predict when no net loss is feasible using biodiversity offsetting. Assuming offset ratios ≤10:1 are indicative of operational feasibility and employing a discount rate of 3%, we predicted that no net loss is feasible where biodiversity can be restored within 55 years, which restricts the impacts on biodiversity that can be offset using restoration. Alternatively, no net loss is feasible by avoiding loss to biodiversity that is declining under the counterfactual at an annual rate ≥6%. However, this is considerably higher than typical background rates of biodiversity loss so restricts where avoided loss offsets are feasible. No net loss is theoretically feasible in the broadest range of circumstances if biodiversity gains are provided in advance of development. However, these gains are procured by restoration or avoided loss, so constraints presented by these approaches also apply. We concluded that no net loss is feasible in a limited range of development scenarios unless offset ratios greater than 10:1 are more widely tolerated.This article is protected by copyright. All rights reserved
Governments should not meet existing conservation targets using the compensation that developers pay for damaging biodiversity, say Martine Maron and colleagues.
Environmental offsetting involves compensating for the residual adverse impacts of an action on the environment by generating an equivalent benefit elsewhere. As the prevalence of environmental offsetting grows, so does the challenge of translating no-net-loss goals to workable policy. From 2011–2012, the Australian Government developed an Environmental Offsets Policy and an accompanying metric (the Offsets Assessment Guide) to support decision making about offset requirements under the Environment Protection and Biodiversity Conservation Act 1999. Through extensive stakeholder consultation and in collaboration with academic researchers, the Guide was developed with the aim of accounting appropriately for ecological equivalence in a transparent and flexible manner. This paper outlines the Australian Government's environmental offset policy development process, and describes the approach adopted for evaluating the suitability of proposed offsets in meeting the policy goals. The Guide explicitly estimates the extent to which an offset will improve the target biota and/or avert future losses, the degree of confidence that the offset will be implemented successfully, and the time it will take to deliver a conservation benefit. Since implementation of the Environmental Offsets Policy and the Guide, there has been a shift in focus from estimating offset requirements based on simplistic area ratios, toward directly evaluating the components of an offset action that determine its environmental performance. Achieving a balance between scientific robustness and policy workability is an ongoing challenge. The Environmental Offsets Policy and Guide represent an important step towards consistency and transparency in environmental offset decision-making.
Biodiversity offsets are an increasingly popular yet controversial tool in conservation. Their popularity lies in their potential to meet the objectives of biodiversity conservation and economic development in tandem, the controversy lies in the need to accept ecological losses in return for uncertain gains. The offsetting approach is seeing widespread adoption, even whilst methodologies and the overriding conceptual framework are still under development.
This review of biodiversity offsetting evaluates implementation to date, synthesizing the outstanding theoretical and practical problems. We begin by outlining criteria that make biodiversity offsets unique, and then explore the suite of conceptual challenges arising from these criteria, whilst indicating potential design solutions.
In practice, we find that biodiversity offset schemes have been inconsistent in meeting conservation objectives. This is as much due to the challenge of ensuring full compliance and effective monitoring as it is to conceptual flaws in the approach itself. Evidence to support this conclusion comes primarily from developed countries, though offsets are increasingly implemented in the developing world.
This is a critical stage at which biodiversity offsets risk becoming a response to immediate development and conservation needs, without an overriding conceptual framework to provide guidance and evaluation criteria. We clarify the meaning of the term 'biodiversity offset', and propose a framework that integrates the consideration of theoretical and practical challenges in the offset process. We also propose a critical research agenda for specific topics around metrics, baselines and uncertainty.
Summary Offsets (also known as mitigation banks, compensatory habitat, set-asides) is a policy instrument recently introduced in several States in Australia to permit some land clearing while striving for no net loss in the extent and condition of native vegetation overall. Offsetting is criticized with respect to the amount of gain required to compensate for losses from clearing, the equivalence of losses and gains, the time lag between losses and gains and a poor record of compliance. Despite these criticisms, we conclude that offsetting is a useful policy instrument while governments continue to permit some clearing of native vegetation. However, offsets will only contribute to no net loss if (i) clearing is restricted to vegetation that is simplified enough so that its functions can be restored elsewhere with confidence or clearing is restricted to vegetation that is unlikely to persist and is not practicable to restore irrespective of clearing; (ii) any temporary loss in habitat between clearing and the maturation of an offset, or differences between the habitat lost from clearing and gained through an offset, does not represent significant risk to a species, population or ecosystem process; (iii) there will be gains of sufficient magnitude on the offset site to compensate for losses from clearing; (iv) best practice adaptive management is applied to offsets; (v) offsets are in place for at least the same duration as the impacts from clearing; and (vi) there is adequate compliance. Land clearing with offsets outside these parameters is inconsistent with ‘no net loss’.
Scattered trees are prominent features in many landscapes worldwide, including natural landscapes, cultural landscapes, and recently modified landscapes. The ecological importance of scattered trees is widely acknowledged in natural landscapes, but has not been sufficiently appreciated in human-modified landscapes. This paper shows that scattered trees are keystone structures in a wide range of landscapes. At the local scale, ecological functions of scattered trees include: provision of a distinct microclimate; increased soil nutrients; increased plant species richness; increased structural complexity; and habitat for animals. At the landscape scale, ecological roles include: increased landscape-scale tree cover; increased connectivity for animals; increased genetic connectivity for tree populations; and provision of genetic material and focal points for future large-scale ecosystem restoration. Furthermore, in disturbed landscapes, scattered trees often are biological legacies that provide ecological continuity through time. In combination, these ecological functions support the argument that scattered trees are keystone structures. That is, their contribution to ecosystem functioning is disproportionately large given the small area occupied and low biomass of any given tree, and the low density of scattered trees collectively. Because scattered trees fulfill unique functional roles in a wide range of scattered tree ecosystems, their loss may result in undesirable ecological regime shifts. A key management challenge in all landscapes with scattered trees is to maintain a balance between recruitment and mortality of trees in an appropriate spatial pattern. Meeting this challenge may represent an important step towards the genuine integration of conservation and production in human-modified landscapes.
Global food demand is growing rapidly. Livestock grazing can provide a valuable source of protein, but conventional grazing is often unsustainable. We studied an 800,000-ha section of a threatened ecoregion in southeastern Australia. Conventional management in the region involves continuous livestock grazing with few rest periods and regular fertilizer application. By using remotely sensed data on tree cover and extensive field data on livestock grazing regimes, soil chemistry, tree diameters, and tree regeneration, we show that the region is facing a tree regeneration crisis. Under conventional management, across the region, millions of hectares of land currently supporting tens of millions of trees will be treeless within decades from now. This would have severe negative ramifications for biodiversity and key ecosystem services, including water infiltration and shade provision for livestock. However, we identified an unexpected win-win solution for tree regeneration and commercial grazing. A relatively new practice in the region is fast-rotational grazing, characterized by prolonged rest periods in between short, intensive grazing events. The probability of regeneration under fast-rotational grazing was up to 4-fold higher than under conventional grazing, and it did not differ significantly from the probability of regeneration in ungrazed areas. In addition, trees were more likely to regenerate where soil nutrient levels were low. These findings suggest that the tree regeneration crisis can be reversed by applying low-input, fast-rotational grazing. New policy settings supporting these practices could signal a turning point for the region, from ecological decline to ecological recovery.
Both permit requirements and ecological assessments have been used to evaluate mitigation success. This analysis combines these two approaches to evaluate mitigation required under Section 404 of the United States Clean Water Act (CWA) and Section 10 of the Rivers and Harbors Act, which allow developers to provide compensatory mitigation for unavoidable impacts to wetlands. This study reviewed permit files and conducted field assessments of mitigation sites to evaluate the effectiveness of mitigation required by the US Army Corps of Engineers for all permits issued in Orange County, California from 1979 through 1993. The 535 permit actions approved during this period allowed 157 ha of impacts. Mitigation was required on 70 of these actions, with 152 ha of enhanced, restored, and created habitat required for 136 ha of impacts. In 15 permit actions, no mitigation project was constructed, but in only two cases was the originally permitted project built; the two cases resulted in an unmitigated loss of 1.6 ha. Of the remaining 55 sites, 55% were successful at meeting the permit conditions while 11% failed to do so. Based on a qualitative assessment of habitat quality, only 16% of the sites could be considered successful and 26% were considered failures. Thus, of the 126 ha of habitat lost due to the 55 projects, only 26 ha of mitigation was considered successful. The low success rate was not due to poor enforcement, although nearly half of the projects did not comply with all permit conditions. Mitigation success could best be improved by requiring mitigation plans to have performance standards based on habitat functions.
An increasing number of Australians want to be assured that the food and fibre being produced on this continent have been grown and harvested in an ecologically sustainable way. Ecologically sustainable farming conserves the array of species that are integral to key ecological processes such as pollination, seed dispersal, natural pest control and the decomposition of waste. Wildlife Conservation in Farm Landscapes communicates new scientific information about best practice ways to integrate conservation and agriculture in the temperate eucalypt woodland belt of eastern Australia. It is based on the large body of scientific literature in this field, as well as long-term studies at 790 permanent sites on over 290 farms extending throughout Victoria, New South Wales and south-east Queensland. Richly illustrated, with chapters on birds, mammals, reptiles, invertebrates and plants, this book illustrates how management interventions can promote nature conservation and what practices have the greatest benefit for biodiversity. Together the new insights in this book inform whole-of-farm planning. Wildlife Conservation in Farm Landscapes is an ideal resource for land managers and farmers interested in integrating farming and environmental values and anyone interested in biodiversity in woodlands and agricultural zones. Recipient of a 2017 Whitley Awards Certificate of Commendation for Conservation in Action
The use of environmental offsets has increased in many parts of the world over the last decade, but assessments of their effectiveness have been rare. We provide the first quantification of the effectiveness of offsets in an Australian State (Western Australia) with an offsets register and history of offset implementation. We determined what outcomes were achieved and the environmental effectiveness of 208 past and current offsets applied as part of environmental approvals between 2004 and 2015 under State jurisdiction legislation. Of the past offsets, we conclude that at most 39% of the offsets studied delivered an outcome and can be considered effective, with land acquisition comparing favourably to other offset types. The outcomes of many offsets were unknown due to reporting too soon after implementation (14%) and inadequate reporting (18%). Thirty percent of past offsets during this time period were found be ineffective through non- or inadequate implementation. We observed significant improvements in the clarity of offset approval conditions over the time period of our study, nonetheless, we suggest that these results provide evidence of the need for better implementation of on-ground management and research into the nature of offsets. We make four suggestions for improvement: 1) timely reporting and compliance with environmental conditions; 2) ensuring approval conditions measure ecological outcomes; 3) improving project planning for offsets; and 4) including contingency and longer term planning in offset design. Conclusions from examining implementation of offsets in Western Australia are likely to be applicable wherever offsets policies are in place or being developed.
Many key questions remain unresolved about how biodiversity responds to temporal increases in native vegetation cover resulting from extensive restoration efforts. We quantified occupancy and colonization probability of old growth, regrowth and planted woodland patches by arboreal marsupials within Australian agricultural landscapes subject to woodland restoration over an 11-year period. Our analyses focused on the common brushtail possum Trichosurus vulpecula and common ringtail possum Pseudocheirus peregrinus. We found strong evidence of a gradient in occupancy levels ranging from highest in old growth woodland, approaching zero in plantings, with regrowth woodland intermediate between these two broad types of vegetation structure. Plantings were not occupied by either species at the outset of our investigation and were rarely colonized throughout the subsequent 10 years. We hypothesize that a lack of shelter sites in large old hollow-bearing trees is one of the key factors limiting the occurrence of plantings by cavity-dependent arboreal marsupials, suggesting a lag between planting establishment and the time required for plantings to become suitable habitat. We found the probability of colonization was positively related to the amount of vegetation cover in the surrounding landscape. Unexpectedly, colonization probability was not influenced by a temporal increase in woody vegetation cover surrounding a patch. A paucity of relationships between patch colonization and the temporal change in vegetation cover may be explained by the fact that most of the increased vegetation cover in our study landscapes over the past decade has resulted from establishment of plantings which are generally not suitable nesting habitat for arboreal marsupials. Our findings have key management implications such as emphasizing the value of old growth woodland for arboreal marsupials and of targeting restoration efforts around old growth and regrowth woodland patches, and the flawed notion of biodiversity offsets that allow replantings to compensate for clearing old growth woodland.
Scattered trees are considered ‘keystone structures’ in many agricultural landscapes worldwide because of the disproportionate effect they have on ecosystem function and biodiversity. Populations of these trees are in decline in many regions. Understanding the processes driving these declines is crucial for better management. Here, we examine the impact of wildfire on populations of this keystone resource. We examined 62 observation plots affected by wildfire and matched with 62 control observation plots where fire was absent. Counts of scattered trees were conducted pre-fire in 2005 and repeated post-fire in 2011. Changes in populations were compared between the control and fire-affected observation plots. Our results show wildfire had a significant local impact, with an average decline of 19.9% in scattered tree populations on burned plots. In contrast, scattered trees increased on average by 5.3% in the control observation plots. The impact of wildfire was amplified (as revealed by greater percentage tree losses) by larger wildfires. Wildfire effects on scattered tree populations are of concern, given a background of other (usually) chronic stressors (often associated with agriculture) and that the frequency and intensity of wildfire are predicted to increase in many landscapes.
The rising popularity of biodiversity offsetting as a tool for balancing biodiversity losses from development with equivalent
gains elsewhere has sparked debate on many fronts. The fundamental questions are the following: Is offsetting good, bad, or
at least better than the status quo for biodiversity conservation outcomes, and what do we need to know to decide? We present
a concise synthesis of the most contentious issues related to biodiversity offsetting, categorized as ethical, social, technical,
or governance challenges. In each case, we discuss avenues for reducing disagreement over these issues and identify those
that are likely to remain unresolved. We argue that there are many risks associated with the unscrutinized expansion of offset
policy. Nevertheless, governments are increasingly adopting offset policies, so working rapidly to clarify and—where possible—to
resolve these issues is essential.
Vegetation restoration is considered as an important strategy for reversing biodiversity decline in agricultural areas. However, revegetated areas often lack key vegetation attributes like large old hollow-bearing trees. As these trees take a long time to develop, artificial cavities such as nest boxes are sometimes provided to address lag effects. We conducted a 3-year experiment using 150 nest boxes with 4 designs to quantify patterns of occupancy within 16 replanted areas and 14 patches of remnant old-growth eucalypt woodland. We quantified patterns of occupancy of nest boxes in physically connected versus isolated remnants and plantings, and multiple covariate effects on nest box occupancy at the nest box, tree, patch, and landscape levels. Our analyses revealed a lower probability of nest box occupancy within remnants (vs. plantings) for 2 of the 6 response variables examined: any species and the Feral Honeybee. Nest boxes in connected remnants and plantings were more likely to be occupied than those in isolated plantings and remnants by any mammal and the Common Brushtail Possum. Nest boxes in restored woodlands are used by some hollow-dependent fauna but principally already common species and not taxa of conservation concern. Nest boxes were also used by pest species. A key management consideration must be to create connected habitat to facilitate colonization of nest boxes by mammals. Approximately 15% of the cavity-dependent vertebrates within the study area used next boxes, possibly because the diverse requirements of the array of other species were not met by the range of nest boxes deployed.
In Australian temperate woodlands, most squirrel glider (Petaurus norfolcensis) habitats exist outside formal conservation reserves, often in highly fragmented agricultural landscapes. To conserve squirrel glider populations in such woodlands it is essential to define important habitats and understand how they are used. This study examines the nocturnal habitat use of squirrel gliders across five sites within an agricultural landscape in south-eastern Australia. Over a five-month period we radio-tracked 32 gliders to 372 nocturnal locations. We quantify characteristics of key nocturnal habitats and describe their use. Gliders were more likely to use large eucalypt trees, particularly yellow box (Eucalyptus melliodora) and mugga ironbark (E. sideroxylon). Nocturnal activity mostly took place high in the canopy of eucalypts, accounting for 74% of fixes. Multiple regression models revealed that feeding was more likely to occur in large, healthy trees close to drainage lines, with a preference for E. melliodora, when eucalypts were not flowering. Flowering trees were preferentially sought and were strongly associated with being large healthy trees that occur on ridges and upper slopes. Showing that the squirrel glider utilises key feeding structures (large healthy Eucalyptus trees) in different parts of the landscape at different times has direct management implications in the conservation and restoration of squirrel glider habitat, particularly in fragmented temperate woodland.
Tree-cavity-dependent wildlife faces future shortages of cavities due to a decline in the abundance of large, old trees in many parts of the world. Nest boxes are proposed as a tool to restore habitat value but evidence of their effectiveness for arboreal mammals remains equivocal. This may arise from a poor understanding of design preferences. We conducted investigations in two landscapes in eastern Australia to determine whether species show a preference for specific designs. We observed a preference by some mammal species for particular designs (33–78% occupied/used), suggesting that design refinement can improve the frequency with which nest boxes are used. Although feral species may out-compete target species for nest boxes, we did not observe this. We recorded feral honeybees (Apis mellifera) in 6–9% of nest boxes but they did not remain, and many occupied boxes were later used by mammals. The introduced common myna bird (Acridotheres tristis) was prevalent in one landscape, but competition for nest boxes was localized. For nest boxes to be an effective habitat restoration tool, they must be able to be occupied over long periods of time. We investigated this for the squirrel glider (Petaurus norfolcensis), an arboreal marsupial threatened through part of its geographic range. Squirrel gliders occupied and bred within nest boxes (100% used) at two locations continuously over a 10-year period with minimal nest box maintenance. Individuals occupied boxes for up to 7 years. This confirms that targeted nest box programs can be an effective restoration tool for cavity-dependent arboreal mammals.
Tree hollows are a critical breeding resource for many organisms globally. Where hollow‐bearing trees are in decline, population limitation can be a serious conservation issue. A particular problem in addressing hollow limitation is the long time that hollows take to form. This means there can be a significant lag time between detecting a species' population decline and arresting the lack of hollows through reducing tree mortality and increasing regeneration. Once underway, declines of hollow‐dependent species therefore can be difficult to halt. It is imperative that we identify and anticipate such future problems before they occur, and implement conservation action in advance. In this study, we use a novel application of an established modelling method to explore this issue and illustrate an ‘early warning’ approach, focusing on a case study of the vulnerable superb parrot Polytelis swainsonii from south‐eastern Australia. The species is dependent on hollow‐bearing trees for nesting that have a very long generation time (> 120 years). Potential nest trees for the superb parrot are on a trajectory of decline. We modelled the future hollow resource for this species under different management scenarios including: (a) business‐as‐usual – that is, no further specific conservation action; (b) and (c) waiting until considerable further reductions (90 and 70%) in hollows before implementing conservation actions to redress loss of hollows; and (d) implementing enhanced conservation actions now to redress loss of hollows. We found that all scenarios except (d), ‘conservation action now’, resulted in substantial declines in potential nest trees, and came at significant opportunity cost in terms of reducing tree mortality and increasing tree regeneration. Delaying conservation action will greatly increase the long‐term risk of extinction of hollow‐dependent species such as the superb parrot. Predicting and slowing the decline in available hollows by early intervention and restoration management is critical, even where hollow‐dependent species populations may appear to be secure in the short‐term.
We explored the main factors affecting the global distribution of tree cavities – a habitat component of mostly biotic origin that is crucial for many animal species. We considered the influence of eight environmental variables (ranging from the single-tree to the biogeographic-region scale) on cavity density in a meta-analysis of 103 published studies. The global median density of cavities was 16ha−1, with densities highest in Australasia and lowest in the Palaearctic region. Two major factors influencing density were identified: cavity density was positively related to the amount of precipitation, and was higher in natural than in managed forests. These effects suggest that the distribution of tree cavities largely reflects the incidence of fungal heart-rot in trees, and that forest management, by affecting wood decay processes, can have a broad-scale impact on tree microhabitat availability. Although air temperature, forest composition and wood hardness had suggestive univariate effects, neither these variables nor biogeographic region explained any additional variation in multifactor models. In regions where woodpeckers are present there was an upper limit to the density of woodpecker-excavated cavities (approximately 10–20cavitiesha−1) that was considerably lower than the highest total cavity densities encountered (up to 140ha−1). This indicates that primary cavity-nesters are particularly important keystone species in cavity-poor forests where wood decay processes are suppressed either climatically or by forest management.
Effective conservation relies on understanding the biology of particular species and how they use key resources. For many arboreal mammals, tree hollows are a key den site. We examined the use of tree hollows by the squirrel glider (Petaurus norfolcensis) in south-eastern Australia. Over a five-month study, individual squirrel gliders used multiple hollow trees (average≤7) as den sites. Den sites were often adjacent to areas where nocturnal activities took place. The average distance between den sites used by individual gliders on successive days was 218m. Dens were often shared by an adult pair and a juvenile. Den trees were disproportionably used, with gliders showing preference for 12 primary den trees often located on steep slopes. Our findings have implications for the number and spatial arrangement of den trees needed to promote the conservation of populations of the squirrel glider, particularly where land is used for agriculture and livestock grazing.
Being able to recognise critical habitat features such as nesting and denning sites is essential for wildlife conservation. It is particularly true for the den trees of species threatened by habitat loss, such as the squirrel glider (Petaurus norfolcensis). Measurements of 146 den trees of the squirrel glider were made in fragmented woodlands of the South-west Slopes of New South Wales and data compared with random trees to quantify the key characteristics of den sites. The likelihood of use as a den tree increased with increasing numbers of visible tree hollows and tree size. Dieback was also a positive indicator of den use. However, when visible hollows within a tree are abundant, dieback-free trees were preferred. Measures of den tree context such as basal area, the number of neighbouring large trees and distance to the next nearest tree, were also found to be important determinants of the likelihood of usage. The above variables were combined into a multiple regression model. The squirrel glider favoured particular Eucalyptus species and some broader eucalypt groups. We believe such variations were most likely due to interspecific differences in hollow development and dieback among the various groups, rather than bark type, a factor previously cited as an important determinant of den tree usage. The 'best' model had high negative predictive power, suggesting it would be useful for identifying (1) trees that could be felled without a loss of this critical habitat resource (e.g. at development sites) and (2) areas unsuitable for potential squirrel glider relocation or habitat enhancement. Squirrel gliders show preference for a combination of tree and tree context features in selecting den trees. Understanding these features will help managers enhance and protect denning resources for this species.