Article

Extinction Debt at Extinction Threshold

Wiley
Conservation Biology
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Abstract

To allow for long-term metapopulation persistence, a network of habitat fragments must satisfy a certain condition in terms of number, size, and spatial configuration of the fragments. The influence of land-scape structure on the threshold condition can be measured by a quantity called metapopulation capacity, which can be calculated for real fragmented landscapes. Habitat loss and fragmentation reduce the metapop-ulation capacity of a landscape and make it less likely that the threshold condition can be met. If the condi-tion is not met, the metapopulation is expected to go extinct, but it takes some time following habitat loss be-fore the extinction will occur, which generates an extinction debt in a community of species. We show that extinction debt is especially great in a community in which many species are close to their extinction thresh-old following habitat loss because the metapopulation-dynamic time delay is especially long in such species. A corollary is that landscapes that have recently experienced substantial habitat loss and fragmentation are ex-pected to show a transient excess of rare species, which represents a previously overlooked signature of extinc-tion debt. We consider a putative example of extinction debt on forest-inhabiting beetles in Finland. At present, the few remaining natural-like forests are distributed evenly throughout southern Finland, but the number of regionally extinct old-growth forest beetles is much greater in the southwestern coastal areas, where human impact on forests has been lengthy, than in the northeastern inland areas, where intensive for-estry started only after World War II. Ignoring time delays in population and metapopulation dynamics will lead to an underestimate of the number of effectively endangered species.

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... Thus, the most well studied consequences of fragmentation are poor recruitment, reduced (functional) connectivity, and associated loss of geneflow caused by long distances between habitat patches [3,12,22]. These studies, for instance, suggest that species with lower dispersal ability and a shorter lifespan should be more sensitive to fragmentation [23], and/or that different organism groups and species will be affected by fragmentation at different spatial and temporal scales [6,18,24]. However, compared to actual islands, forest stands will fall along a gradient from effectively continuous populations, to functioning meta-populations with a balance of extinction and (re)colonization, to non-viable meta-populations where sub-populations lose connectivity and slowly disappear [25,26]. ...
... Given the critical value of the remaining natural boreal forest, the continued forest harvesting and land use change, and the importance of dispersal and landscape permeability for species diversity, it is logical to assume a substantial effect of fragmentation on both incidence and abundance of conservation-relevant species in boreal forest stands. Furthermore, the slow turn over, combined with that many boreal forest species are highly specialised and recognised as threatened [51], suggests high risk for extinction debt in this zone [13,23,24,38]. Lastly, the boreal zone has large landscape variation due to differences in historical land-use and level of human impact [3,46,47,52], suggesting a high availability of comparisons to study. ...
... Furthermore, we identified a number of sub hypothesis or secondary questions related to how the landscape effect is manifested and depend on a range of factors. The extent of the effect may differ among organism groups and, for instance, be higher for groups with poor dispersal ability [23]. The extent of the effect may also depend on the exact aspect of the landscape analysed, i.e. the explanatory power will be higher if a variable more important to the organism has been quantified [6]. ...
Article
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Background Forestry and land-use change are leading causes of habitat loss, degradation, and fragmentation worldwide. The boreal forest biome is no exception, and only a small proportion of this forest type remains intact. Since forestry will remain a major land-use in this region, measures must be taken to ensure forest dependent biodiversity. Stand level features and structures promoting conservation relevant species have received much attention, but the landscape level perspective is often missing. Hence, we review the literature that has related fragmentation in the surrounding landscape to occurrence of threatened, declining, red-listed, rare, or deadwood dependent species as well as those considered to be indicator, flagship, umbrella, and/or keystone species in a given boreal forest stand. Methods A comprehensive search string was developed, benchmarked, and adapted for four bibliographic databases, two search engines, and 37 specialist websites. The online evidence synthesis tool Cadima was used for screening of both abstracts and full texts. All articles meeting the inclusion criteria were subject to study validity assessment and included in a narrative table. Studies reporting means and variance were included in quantitative meta-analysis when more than 3 comparable studies were available. Results The searches resulted in 20 890 unique articles that were reduced to 172 studies from 153 articles. These studies related stand level presence, abundance, species richness, and/or composition of conservation relevant species to landscape factors such as: categorical fragmentation intensity (higher vs. lower), amount of habitat or non-habitat, distance to habitat, and/or habitat configuration, on scales ranging from tens to tens of thousands of ha. Forty-three studies were suitable for meta-analysis. These showed a significant negative effect of fragmentation on both presence and abundance of conservation relevant species, as well as a near significant trend for species richness. This was particularly clear when fragmentation was measured as distance to surrounding habitat for presence, and as habitat amount for abundance. The organism groups with the strongest support for a negative effect of fragmentation were wood fungi and birds. Conclusion As hypothesised, there is strong support for negative effects of fragmentation in boreal forest. These results emphasize the negative consequences of the intensive forestry and associated landscape transformation that has been the norm for the last century. We argue that this should have direct implications for policy makers to shift towards including a landscape perspective in all planning of harvesting, preserving, and restoring forest. In addition, we found that research effort has been very uneven between organism groups, that studies on landscape change over time were rare, and that many studies have not quantified the difference in fragmentation intensity among landscapes making it difficult to quantify the extent of the negative effect. One way forward would be to revisit the studies included here in to incorporate change over time, as well as a true quantification of landscape fragmentation. By doing so, the scale of the negative effects would be much better analysed, which would greatly assist conservation practitioners all throughout the boreal forest biome.
... Dead wood is an exceptionally important habitat feature for many insects and other taxa in boreal forests, with studies showing an increase in abundance and richness of saproxylic insects with increasing amounts of dead wood (Sandström et al. 2019), including in fruiting bodies of wooddecaying macrofungi, which can be considered hotspots of boreal forest insect diversity (Komonen 2003). The effect of removal of woody biomass from large areas of the landscape on the rest of the soil food web, and the functioning of the boreal ecosystem as a carbon sink, is likely to be severe but may not always be evident as the extinction debt takes time to be paid (Hanski and Ovaskainen 2002). ...
... Ecologically sensitive management must, however, consider the possibility of extinction debtthe future extinction of a species due to past and/or current activities. Boreal forests had lower extinction rates of beetle species the shorter they were exposed to industrial forestry practices (Hanski and Ovaskainen 2002). Indeed, many beetle species could eventually disappear from the landscape without the presence of old-growth forest refugia (Niemelä et al. 2007). ...
... Indeed, many beetle species could eventually disappear from the landscape without the presence of old-growth forest refugia (Niemelä et al. 2007). To prevent this, forest management should, where possible, mimic natural disturbance when harvesting timber, maintain natural vegetation and old-growth forests across the forestry landscape, and ensure structural and compositional variation exists at the landscape level (Hanski and Ovaskainen 2002;Niemelä et al. 2007, see also the EMEND project: https://emend.ualberta.ca/). ...
... Importantly, changes in species abundance or diversity of communities associated with foundation species may not occur immediately after a disturbance, resulting in extinction debt, or a significant time delay prior to the disappearance or local extinction of a species from a particular habitat patch (Tilman et al. 1994, Kuussaari et al. 2009, Watts et al. 2020. Problematically, assessing post-disturbance community-wide biodiversity loss before extinction debt has been paid could lead to incorrect estimation (usually an underestimation) of the number and types of associated species vulnerable to local extinction (Hanski & Ovaskainen 2002, Watts et al. 2020. ...
... Overall high mobility of the fish, crustacean, and echinoderm fauna associated with live and dead corals suggests that active dispersal could explain the surge of species richness in the dead coral habitats between July 2008-January 2009 and the increase in abundance of Trapezia crabs in live corals. Our results also suggest that a metapopulation perspective (Hanski & Ovaskainen 2002) may be a useful conceptual framework for investigating post-disturbance patterns of live and dead coral habitat occupancy, at least in this system of discrete finger corals in the Galápagos, and for tropical reefs of other regions where disturbances result in increasingly patchily and sparsely-distributed branching coral colonies. ...
... obs.). As in most communities of mobile species such as birds (Watts et al. 2020), insects (Hanski & Ovaskainen 2002), and reef fishes (Kritzer & Sale 2006), the community of fishes and macroinvertebrates associated with live and dead finger corals represents a mix of habitat and food specialists and generalists. Future research to identify habitat specialist species on Galápagos reefs is needed to understand those species most vulnerable to habitat loss and to overall biodiversity loss following future temperature stress from climate oscillations. ...
Preprint
During a cold La Niña period (August 2007-January 2008) in the central Galápagos archipelago, 70% of Pocillopora finger corals were bleached across three long-term monitoring sites, affording an opportunity to examine the impact of El Niño Southern Oscillation-related temperature anomalies on the persistence of these corals and their associated community of fish and mobile macroinvertebrates. Using a time series empirical approach, we tagged and tracked the fate of 96 coral heads and their associates. When surveyed in July 2008, live (recovered) and dead corals supported similar levels of randomized observed species richness and Chao 1 estimated species richness. Whereas richness on the surviving live corals remained fairly stable, Chao 1 estimated richness on dead corals underwent a nearly 50% increase between July and January 2009, thereafter declining to 50% of originally surveyed richness by February 2010. This nonlinear change in species richness was largely due to influx and decline in opportunistic generalists including pencil urchin bioeroders, gastropod snails, and hermit crabs that colonized dead corals and fed on sessile invertebrates and algae that had initially recruited to dead and undefended coral substrate. Thus, dead corals retained high overall species richness until live corals had recovered; after which richness declined as dead corals eroded and disappeared (July 2011). Live corals attracted a less speciose but stable assemblage of mutualistic xanthid crabs and fishes that increased in abundance over time with the recovery and growth of live coral tissue. Overall, three physical features of the finger coral habitats (coral vital status, total surface area, and maximum branch length) predicted the number of species associated with each colony. The delayed diversity loss of associated species following La Niña disturbance to a foundation species represents a local extinction debt of 32-49-month duration. A better understanding of the scale of extinction debt in foundational marine ecosystems is needed to quantify the breadth of impacts of climate oscillations on biodiversity and ecosystem functioning.
... Adding fragmentation of old-growth forests and reports of extinction debts (e.g. Hanski & Ovaskainen, 2002), we may be approaching a tipping point for biodiversity (Barnosky et al., 2012). ...
... Recurrent fragmentation in a landscape (Tilman et al., 1994) and potentially, repeated clear-cutting events, can accelerate this effect. According to Hanski & Ovaskainen (2002), extinction debts can be seen by the many rare species present in fragmented old-growth forests, such as beetles in northeastern Finland. Similarly, three out of four fungal species associated with dead wood in old-growth forests showed a time-lagged negative response to landscape changes in eastern Finland (Gu, Heikkilä & Hanski, 2002). ...
Article
Boreal forests are important carbon sinks and host a diverse array of species that provide important ecosystem functions. Boreal forests have a long history of intensive forestry, in which even-aged management with clear-cutting has been the dominant harvesting practice for the past 50–80 years. As a second cycle of clear-cutting is emerging, there is an urgent need to examine the effects of repeated clear-cutting events on biodiversity. Clear-cutting has led to reduced numbers of old and large trees, decreased volumes of dead wood of varied decay stages and diameters, and altered physical and chemical compositions of soils. The old-growth boreal forest has been fragmented and considerably reduced. Here, we review short- and long-term (≥50 years) effects of clear-cutting on boreal forest biodiversity in four key substrates: living trees, dead wood, ground and soil. We then assess landscape-level changes (habitat fragmentation and edge effects) on this biodiversity. There is evidence for long-term community changes after clear-cutting for several taxa: epiphytic lichens; saproxylic fungi, bryophytes and insects; epigeic bryophytes; and soil snails, bacteria, and ectomycorrhizal fungi. Long-term declines in species richness were found for saproxylic fungi, bryophytes and true flies. However, for the majority of taxa, long-term effects of clear-cutting are not well understood. On the landscape level, reduced connectivity to old-growth forests has negative effects on several species of fungi, lichens, bryophytes and insects, notably among Red-Listed species. Furthermore, altered microclimate near clear-cut edges negatively affects epiphytic lichens and epigeic arthropods, implying complex effects of habitat fragmentation. Repeated cycles of clear-cutting might pose even stronger pressures on boreal forest biodiversity due to continued fragmentation of old-growth forests and accumulation of extinction debts. Examining the broad effects of forestry on biodiversity across the boreal biome is crucial: (i) to increase our knowledge of long-term and landscape-level effects of former clear-cutting; and (ii) to gain a better understanding of how forestry will affect biodiversity and, subsequently, ecosystem functioning, with repeated cycles of clear-cutting.
... In fact, cereal yields as prominent intensification indictor are stagnating for all CEE countries since 1990 (Brisson et al. 2010;Liira et al. 2008). In this respect, the fundamental incongruity is that most extinctions of species should already have occurred due to realized habitat loss long time ago, which is usually true for short-lived specialist species, e.g., insects, annual plants and for small fragmented habitats (Hanski and Ovaskainen 2002;Krauss et al. 2010). Conversely, ecological legacy effects might still be pending, most likely in cases of long-lived species, e.g., perennial plants, mammals on large and connected habitats where persistent extinction is often described as (co-)extinction debt in a metapopulation context (e.g., Culbert et al. 2017;Deák et al. 2021;Kuussaari et al. 2009;Löffler, Poniatowski, and Fartmann 2020). ...
... Conversely, ecological legacy effects might still be pending, most likely in cases of long-lived species, e.g., perennial plants, mammals on large and connected habitats where persistent extinction is often described as (co-)extinction debt in a metapopulation context (e.g., Culbert et al. 2017;Deák et al. 2021;Kuussaari et al. 2009;Löffler, Poniatowski, and Fartmann 2020). In fragmented landscapes, delayed (co-)extinction is facilitated by increasing habitat numbers and area, decreasing habitat isolation and temporally close habitat destruction time (with variable time spans of debt duration between 5 and 1000 years) (Figueiredo et al. 2019;Hanski and Ovaskainen 2002;Hylander and Ehrlén 2013). It is clearly evident that biodiversity dynamics can only be understood against this background of patterns and processes concerning the dynamic configuration of remaining habitat fragments in a landscape context. ...
Article
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A dramatic decrease of biodiversity is currently questioning human‐environment interactions that have shaped ecosystems over thousands of years. In old cultural landscapes of Central and East European (CEE) countries, a vast species decline has been reported for various taxa although intensive land cultivation has been reduced in favor of agroecological transformation, nature conservation and sustainable land management in the past 30 years. Thus, in the recent history, agricultural intensification cannot solely be discussed as the major driver controlling biodiversity. In cultural landscapes, we state that drivers and pressures mainly emerge from the backyards of rural settlements that act as interconnected rural hotspots and therefore form an ecological metapopulation in which small‐scale backyard habitats are capable of preserving and exchanging species pools of the historical cultural landscape. We further argue that shifting sociocultural norms significantly affecting the survival of source populations in rural hotspots and drastically limit their dispersal pathways, which triggers the degradation of the rural metapopulation in recent times. Pressures of cultivation shift, landscape decoupling, structural homogenization, and use of technology and agrochemicals are identified as backyard ecological drivers negatively affecting biodiversity preservation, particularly in the surrounding rural landscape. Spatiotemporal dimensions of backyard pressures involving material fluxes, species exchange and retention, alternation of site conditions, and local genetic adaptation are delineated for different backyard features, including building structures, gardens, lawns, and paved grounds. Finally, we propose a future research agenda to quantify effects and trends of rural hotspots and followed patterns of altered species dynamics. We give an example on the use of satellite time series to remotely map rural backyard habitats and reveal significant spatiotemporal trends induced by small‐scale human behavior that may lead to a new socioecological perception and stimulate actions to shape ecological dynamics emerging from the backyards of human settlements.
... We refer to the increase in ecosystem function after habitat disturbance as ecosystem function credit. Extinction debt attracts the most attention because it provides time windows for conservation actions to rescue rare species from extinction (Hanski and Ovaskainen 2002;Malanson 2008;Wearn, Reuman, and Ewers 2012;Halley, Sgardeli, and Triantis 2014;Highland and Jones 2014;Chen and Peng 2017;Otto et al. 2017;Figueiredo et al. 2019;Makishima et al. 2021;Ridding et al. 2021). However, studies of ecosystem function debt/credit are limited (also mentioned by Gonzalez, Mouquet, and Loreau 2009), and as far as we know, none of these studies consider a heterogeneous landscape. ...
... Similar definitions are used in the other studies (Kuussaari et al. 2009;Jackson and Sax 2010;Halley et al. 2016;Figueiredo et al. 2019). Meanwhile, a given species' extinction risk could be measured by the time delay index, that is, the persistence time of extinct species since habitat loss (Hanski and Ovaskainen 2002). If the time delay index of a species is higher, its extinction risk is lower (Grimm and Wissel 2004). ...
Article
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Aim Habitat destruction causes “extinction debt” and is also thought to produce ecosystem function debt, but theory of their magnitude and nature is limited. Heterogeneous landscapes are fundamental to the maintenance of species richness and ecosystem function, while directed or undirected dispersal behaviour, such as dispersal of seeds by animals or by the wind, is also important, especially after habitat destruction. We therefore consider extinction and ecosystem function debt under different dispersal rates and behaviours in heterogeneous landscapes. Methods We use a classic heterogeneous metacommunity model to capture the dynamics of competing species in local patches linked by dispersal and varying in environmental conditions. We remove one patch at a time and measure extinction debt and ecosystem function debt by the number/proportion of delayed extinctions and the amount of biomass change, respectively. Results We reveal three species extinction regimes as dispersal increases: (1). species most adapted to the removed habitat are most at risk; (2). similarly adapted species are also at risk; (3). patch removal shifts competitive balance among the few species coexisting at high dispersal, where competition is strong. We find surprisingly that destruction of habitat can hasten the extinction of those species best adapted to harsh environments and that the proportion of diversity at risk from extinction actually increases with dispersal because competition is intense there. Finally, there can be a small ecosystem credit but extinction debt when dispersers reroute to potentially more favourable remaining habitats (directed dispersal), especially when harsh environments are removed. However, ecosystem debt occurs and can be large under undirected dispersal. Main Conclusions The magnitude and nature of extinction and ecosystem function debts depend on species dispersal rates and behaviours, as well as the environmental conditions of the disturbed habitats. Conservation actions will be more successful if they consider these factors.
... Such habitat loss has likely led to the disappearance of species over large areas of Australia, with some threatened species experiencing broad-scale extirpation (Ward et al. 2022). Even for species not apparently in decline, the modification and fragmentation of habitat may result in extinction debts (Tilman et al. 1994;Hanski and Ovaskainen 2002). A compounding issue for bird conservation is the geographical biases in habitat loss, which may disproportionately affect species with small ranges (which can already be predisposed to extinction (Harris and Pimm 2008), and particular habitat associations. ...
... For instance, recent research has shown that birds foraging in agricultural lands are exposed to, and experience varied effects from, neonicotinoid insecticides (Lennon et al. 2019(Lennon et al. , 2020, while those in urban environments may not be able to satisfy their nutritional requirements (Meillère et al. 2015). Coupled with the ongoing threat of habitat loss this may result in extinction debt in the long-term (Tilman et al. 1994;Hanski and Ovaskainen 2002). ...
Article
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Australia has lost vast areas of its natural vegetation through agriculture and urbanization, resulting in the area of suitable habitat for many Australian bird species being greatly diminished. Given the geographical and ecological biases in anthropogenic land use, the impact of habitat loss now and into the future may be disproportionately high for some species, threatening their long-term persistence. Such changes are occurring rapidly, and habitat loss needs to be monitored dynamically to prevent extinction. To monitor changes in available unmodified species habitat, we use species’ area of feeding habitat (AFH), which represents the area of habitat within a species’ range with vegetation matching their feeding requirements. We analysed the past, current and future threats of habitat modification for 467 Australian bird species by calculating AFH across three time periods: pre-colonization, current (2020), and a projected future scenario (2100). These values were used to identify species subject to substantial habitat loss due to urbanization and agriculture and delineate predictors of such losses. Most species had experienced habitat loss since colonization (n = 442, 95%), and species that had already experienced considerable habitat loss were more likely to lose habitat into the future. Species with particular habitat associations (e.g., Mallee), were also more prone to greater proportions of habitat lost. The results highlight the utility of AFH and emphasize the importance of protecting what habitat remains for the species with highly depleted geographic ranges, noting that those that have experienced the most loss of unmodified habitat are the most likely to lose more unmodified habitat under future conditions.
... This understanding is important for landscape-level conservation efforts in which choices are made about the protection (or allowing the destruction) of some fraction of the existing patches. If a critical number of the sources patches are lost, then the entire metapopulation will collapse (Hanski and Ovaskainen, 2002). Unfortunately, patch occupancy alone is not a reliable indicator of the source/sink status of individual patches. ...
... Eventually, these species will go extinct in this landscape, but extinction is delayed by the presence of long-lived individuals and some low levels of reproduction. This delay is termed ''extinction debt'' (Hanski and Ovaskainen, 2002;Honnay et al., 2005), and it depends on the life history of species affected by habitat fragmentation (Piqueray et al., 2011). Krauss et al. (2010) reviewed data for a variety of species living in fragmented grasslands of Europe. ...
... Decreases in habitats size caused by human activities are predicted to cause species loss, and the impacts would be more severe for organisms of higher trophic levels (Crooks et al., 2017;Post et al., 2000;Schoener, 1989). As it takes time for extinction events to occur, many species that persist now may have already been doomed, and such "extinction debt" will be paid in the not-too-distant future (Hanski & Ovaskainen, 2002;Tilman et al., 1994). Here, our study suggests a new mechanism for habitat reduction F I G U R E 2 Bacterial density (colony-forming units [CFUs] per milliliter) of microcosms at (a) the beginning and (b) the end of the experiment. ...
Article
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Populations in antagonistic coevolutionary interactions may “run or die,” and their fates are determined by their evolutionary potential. The asymmetry of evolutionary speed between coevolving partners, for example, resulting from genetic constraints, can be mitigated in larger populations. We therefore hypothesize more frequent extinction driven by antagonistic coevolution with declining habitat size. In bacterium‐virus systems, viruses (the consumers) typically suffer an evolutionary disadvantage due to constraints of genetic variation; and this pattern may apply to host–parasite interactions in general. Here, in our experiment with the bacterium Pseudomonas fluorescens SBW25 and its lytic phage virus SBW25Φ2, the likelihood of viral extinction was greater in smaller habitats. Among viral populations that did persist, those from small habitats showed lower infectivity and their coevolving bacterial populations had greater densities. Therefore, the impact of habitat size reduction on biodiversity could be exacerbated by coevolutionary processes. Our results also lead to a number of suggestions for biocontrol practices, particularly for evolutionary training of phages.
... Habitat loss is a global key threatening process to vertebrates, particularly herpetofauna due to their dependence on the environment for regulation of body temperature (White et al. 1997). Because of often considerable lag times between habitat loss and extinction for many fauna, the consequences of the current level of habitat loss have not yet been realised (Tilman et al. 1994;Hanski and Ovaskainen 2002;Kuussaari et al. 2009;Jackson and Sax 2010). ...
... The sum of core and satellite species is a qualitative approximation for the number of species that can potentially persist. Alternatively, the proportion of transient species in the network (1-persistence), can be interpreted as the "extinction debt" of the community (Hanski & Ovaskainen, 2002;Kuussaari et al., 2009), and represents the minimum proportion of species that would become extinct under the current environmental conditions once plants occupy all the space suitable for recruitment in the locality. Disturbancedependent transients could persist if there are recurrent disturbances of sufficient spatial extent and short return time. ...
Article
Full-text available
Plant-plant interactions are major determinants of the dynamics of terrestrial ecosystems. There is a long tradition in the study of these interactions, their mechanisms and their consequences using experimental, observational and theoretical approaches. Empirical studies overwhelmingly focus at the level of species pairs or small sets of species. Although empirical data on these interactions at the community level are scarce, such studies have gained pace in the last decade. Studying plant-plant interactions at the community level requires knowledge of which species interact with which others, so an ecological networks approach must be incorporated into the basic toolbox of plant community ecology. The concept of recruitment networks (RNs) provides an integrative framework and new insights for many topics in the field of plant community ecology. RNs synthesise the set of canopy-recruit interactions in a local plant assemblage. Canopy-recruit interactions describe which ("canopy") species allow the recruitment of other species in their vicinity and how. Here we critically review basic concepts of ecological network theory as they apply to RNs. We use RecruitNet, a recently published worldwide data set of canopy-recruit interactions, to describe RN patterns emerging at the interaction, species , and community levels, and relate them to different abiotic gradients. Our results show that RNs can be sampled with high accuracy. The studies included in RecruitNet show a very high mean network completeness (95%), indicating that undetected canopy-recruit pairs must be few and occur very infrequently. Across 351,064 canopy-recruit pairs analysed, the effect of the interaction on recruitment was neutral in an average of 69% of the interactions per community, but the remaining interactions were positive (i.e. facilitative) five times more often than negative (i.e. competitive), and positive interactions had twice the strength of negative ones. Moreover, the frequency and strength of facilitation increases along a climatic aridity gradient worldwide, so the demography of plant communities is increasingly strongly dependent on facilitation as aridity increases. At network level, species can be ascribed to four functional types depending on their position in the network: core, satellite, strict transients and disturbance-dependent transients. This functional structure can allow a rough estimation of which species are more likely to persist. In RecruitNet communities, this functional structure most often departs from random null model expectation and could allow on average the persistence of 77% of the species in a local community. The functional structure of RNs also varies along the aridity gradient, but differently in shrubland than in forest communities. This variation suggests an increase in the probability of species persistence with aridity in forests , while such probability remains roughly constant along the gradient in shrublands. The different functional structure of RNs between forests and shrublands could contribute to explaining their co-occurrence as alternative stable states of the vegetation under the same climatic conditions. This review is not exhaustive of all the topics that can be addressed using the framework of RNs, but instead aims to present some of the interesting insights that it can bring to the field of plant community ecology.
... The sum of core and satellite species is a qualitative approximation for the number of species that can potentially persist. Alternatively, the proportion of transient species in the network (1-persistence), can be interpreted as the "extinction debt" of the community (Hanski & Ovaskainen, 2002;Kuussaari et al., 2009), and represents the minimum proportion of species that would become extinct under the current environmental conditions once plants occupy all the space suitable for recruitment in the locality. Disturbancedependent transients could persist if there are recurrent disturbances of sufficient spatial extent and short return time. ...
Article
Full-text available
Plant–plant interactions are major determinants of the dynamics of terrestrial ecosystems. There is a long tradition in the study of these interactions, their mechanisms and their consequences using experimental, observational and theoretical approaches. Empirical studies overwhelmingly focus at the level of species pairs or small sets of species. Although empirical data on these interactions at the community level are scarce, such studies have gained pace in the last decade. Studying plant–plant interactions at the community level requires knowledge of which species interact with which others, so an ecological networks approach must be incorporated into the basic toolbox of plant community ecology. The concept of recruitment networks (RNs) provides an integrative framework and new insights for many topics in the field of plant community ecology. RNs synthesise the set of canopy–recruit interactions in a local plant assemblage. Canopy–recruit interactions describe which (“canopy”) species allow the recruitment of other species in their vicinity and how. Here we critically review basic concepts of ecological network theory as they apply to RNs. We use RecruitNet, a recently published worldwide data set of canopy–recruit interactions, to describe RN patterns emerging at the interaction, species, and community levels, and relate them to different abiotic gradients. Our results show that RNs can be sampled with high accuracy. The studies included in RecruitNet show a very high mean network completeness (95%), indicating that undetected canopy–recruit pairs must be few and occur very infrequently. Across 351,064 canopy–recruit pairs analysed, the effect of the interaction on recruitment was neutral in an average of 69% of the interactions per community, but the remaining interactions were positive (i.e. facilitative) five times more often than negative (i.e. competitive), and positive interactions had twice the strength of negative ones. Moreover, the frequency and strength of facilitation increases along a climatic aridity gradient worldwide, so the demography of plant communities is increasingly strongly dependent on facilitation as aridity increases. At network level, species can be ascribed to four functional types depending on their position in the network: core, satellite, strict transients and disturbance-dependent transients. This functional structure can allow a rough estimation of which species are more likely to persist. In RecruitNet communities, this functional structure most often departs from random null model expectation and could allow on average the persistence of 77% of the species in a local community. The functional structure of RNs also varies along the aridity gradient, but differently in shrubland than in forest communities. This variation suggests an increase in the probability of species persistence with aridity in forests, while such probability remains roughly constant along the gradient in shrublands. The different functional structure of RNs between forests and shrublands could contribute to explaining their co-occurrence as alternative stable states of the vegetation under the same climatic conditions. This review is not exhaustive of all the topics that can be addressed using the framework of RNs, but instead aims to present some of the interesting insights that it can bring to the field of plant community ecology.
... The deadline for habitat restoration is therefore quite sensitive to small changes in ̂ near D*, and habitat destruction just over the critical value D* may allow very long deadlines for habitat restoration. This outcome relates closely to Hanski and Ovaskainen's prediction that species just past an extinction threshold exhibit a particularly large time delay to extinction [Hanski 2002]. Though Hanski and Ovaskainen were concerned with time to extinction rather than to an Allee threshold, the slowness of transient dynamics near a bifurcation underlies both phenomena. ...
Preprint
Habitat destruction threatens the viability of many populations, but its full consequences can take considerable time to unfold. Much of the discourse surrounding extinction debts--the number of species that persist transiently following habitat loss, despite being headed for extinction--frames ultimate population crashes as the means of settling the debt. However, slow population decline also opens an opportunity to repay the debt by restoring habitat. The timing necessary for such habitat restoration to rescue a population from extinction has not been well studied. Here we determine habitat restoration deadlines for a spatially implicit Levins/Tilman population model modified by an Allee effect. We find that conditions that hinder detection of an extinction debt also provide forgiving restoration timeframes. Our results highlight the importance of transient dynamics in restoration and suggest the beginnings of an analytic theory to understand outcomes of temporary press perturbations in a broad class of ecological systems.
... In fact, the interrelation of factors as diverse as climate, access to resources, predators and human activity, makes it necessary to develop mathematical models that allow predicting the effect of each of them on the species involved, showing possible scenarios of coexistence or extinction. A large number of publications on topics such as predator-prey models [1,2,3], intra-and inter-specific competition [4,5,6], or habitat fragmentation [7,8,9] can be found, but more research is still needed on how to integrate all these mechanisms together. ...
Preprint
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We develop a mathematical model of extinction and coexistence in a generic predator-prey ecosystem composed of two herbivores in asymmetrical competition and a hunter exerting a predatory pressure on both species. With the aim of representing the satiety of hunters when preys are overabundant, we introduce for the predation behavior a dependence on preys density. Specifically, predation is modeled as growing proportionally to the presence of herbivores at low density, and saturating when the total population of prey is sufficiently large. The model predicts the existence of different regimes depending on the parameters considered: survival of a single species, coexistence of two species and extinction of the third one, and coexistence of the three species. But more interestingly, in some regions parameters space the solutions oscillate in time, both as a transient phenomena and as persistent oscillations of constant amplitude. The phenomenon is not present for the more idealized linear predation model, suggesting that it can be the source of real ecosystems oscillations.
... This is often the case especially for biodiversity, as species' complex interactions and spatial population dynamics can result in a considerable delay before populations reach the levels supported by the changed environment (e.g. Hanski and Ovaskainen 2002). Thus, continuing the current practice does not guarantee that carbon stock or biodiversity will stay at the current level. ...
Article
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Purpose Carbon and biodiversity footprints are increasingly calculated. However, little attention has been paid to the coherency of methodological choices and interpretation of the footprint results. This paper aims to clarify the coherency between the choice of reference land use and carbon and biodiversity footprints and discuss the challenges encountered. Methods First, we analyse features of reference land use options proposed in ISO 14067 (2018) i.e. business as usual, projected future, target, potential natural regeneration and historic baseline. Second, we discuss the connection between temporal scope and life cycle of land use. Third, we provide guidance on how to choose reference land use coherently. Fourth, we discuss specific issues related to carbon and biodiversity footprints and their relationship to reference land use. Finally, we provide conclusions and recommendations for further conceptual development. Results and discussion Choice of reference land use and determination of temporal scope of a study may significantly influence the assessment of carbon or biodiversity footprints. If the aim of a footprint study is to assess the effects of land use, reference land use should describe dynamically non-use of land. Thus, potential natural regeneration or continuation of natural state (if it is the starting point) of land is the coherent reference land use in this case. If the aim of a footprint study is to assess the effects of a decision to change land use or its management, reference land use should describe dynamically alternative use of land expected without the studied decision. Business as usual or projected future is a coherent reference land use in this case. Historic baseline or target reference land use may be useful in comparing the ecosystem value of the studied land use with a pre-set historic baseline or (policy) target. Conclusions We conclude that coherent choice of reference land use for carbon or biodiversity footprints depends on the goal and scope of a study. Beyond methodological coherency, issues related to the reliability and availability of appropriate data are relevant and vary between reference land use choices. However, difficulties in the assessment should not justify incoherent choices. We recommend that uncertainties are not overlooked but incorporated in the assessment and considered in the interpretation of the results. In addition, we recommend that key methodological choices, including the definition of the purpose of a study, chosen temporal scope and applied reference land use, should be clearly and transparently presented.
... The past forest cover is likely mainly affected by historical logging. This, so called, extinction debt (see Hanski, and Ovaskainen, 2002), is a time delay in the effects of habitat loss on bird populations. Kumpula et al. (2023) has earlier shown that forest cutting has a cumulative effect on willow tit numbers and thus logging history at least up to 30 years can influence population dynamics. ...
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Understanding how anthropogenetic change affects populations of species is crucial to halt the loss of biodiversity. Although habitat loss and degradation are key drivers of population declines, the exact demographic mechanisms are seldom well understood. Here, we investigated how habitat availability and changes in habitat availability were related to large-scale changes in the breeding and winter populations of a rapidly declining forest species, the willow tit Poecile montanus, in Northern Europe. In addition, we examined the effects of potential competitors (the great tit Parus major and the blue tit Cyanistes caeruleus) and their predator (the great spotted woodpecker Dendrocopos major) on long-term population changes. We also investigated long-term trends in adult survival and recruitment. Changes in breeding numbers were positively associated with the availability of older forest and changes in great tit numbers, but not significantly associated to short-term changes in forest cover or the abundance of nest predator, great spotted woodpeckers. Site level population changes during winter-a proxy for survival rates-were positively associated with the amount of older forest, but were not affected by temperature. The capture-recapture study showed a strong decline in adult survival, but the per capita recruitment rate showed no clear trend. As adult survival has a large contribution to the population growth rate, our results suggest that the willow tit population decline is mainly caused by decreased adult survival rates during non-breeding season. Given that logging volumes have been increasing in recent decades in the area, the reduced habitat quality and loss of older forests are likely the key drivers of the overall population decline.
... Due to the habitat loss and fragmentation, several abundant species may become rare and go extinct. Models indicate that when habitat loss occurs, it may result in time-delayed species extinction, referred to as extinction debt, where the natural demographic functions of the population are no longer sustainable Hanski 2000;Hanski and Ovaskainen 2002). Tilman et al. (1994) suggest that the gradual and predictable disappearance of organisms is most likely in the case of dominant and efficient resource users, which can lead to increased intraand inter-specific resource competition (Samia and Lutscher 2010;Cheng et al. 2019). ...
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The distribution of species in a patchy habitat may be influenced by competitive interactions. The dominant and highly competitive boreal ant species belong to the Formica rufa group. A pair of species, Formica aquilonia and Formica polyctena, require extensive territories due to their multi-nest breeding habits. The coexistence and habitat patterns of these two wood ant species in the boreal forest landscape were investigated. Forest characteristics in the vicinity of nests in forest patches were similar for both species, but they did not coexist in the same sampling plots of 0.79 ha in forest patches, indicating competitive exclusion. The sampling plots in large forest patches were more occupied by F. aquilonia, while no such association was found for F. polyctena. At a larger spatial scale (78.5 ha), we found that F. polyctena was more tolerant of smaller forest patches than F. aquilonia suggesting that these two ant species can coexist in moderately fragmented forest landscapes. However, forest habitat loss, fragmentation and climate-induced changes in forest tree structure may shift the species balance in favour of F. polyctena over F. aquilonia in the future.
... Intensive agricultural land use limits gene flow among population and fragment habitats available to any particular species. Where individuals of animal species are unable to move through agricultural fields, populations will become more isolated, further reducing effective population sizes and threatening the viability of these populations (Hanski and Ovaskainen, 2002). ...
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The past decades have witnessed a dramatic change in agriculture with food production soaring due to the Green Revolution. The Green Revolution entails agricultural intensification through excessive and sometimes inappropriate use of chemical fertilizers and pesticides which has polluted water bodies and degraded soils, led to biodiversity loss by killing beneficial plants, insects and other wildlife and in some cases poisoned farm workers. The study assessed the side effects of intensive agricultural production on environment in Benue State, Nigeria. The major objective of the study was to examine the side effects of intensive agriculture on environment, while the specific objectives were to identify major the problems caused by intensive farming, find out major benefits of intensive farming, ascertain the effects of intensive farming on the soil and examine ways of reducing intensive farming. Primary data were gathered by survey using structured questionnaire administered on 115 respondents (farmers/labourers working in intensive farms) were selected randomly from five different farms. Data gathered were analyzed through descriptive statistics which revealed that farm accidents with machines 87.9%, availability of food throughout the year 94.8%, destruction of soil organic matter 61.7% and practicing organic agriculture 33.95%. It is recommended that operators of farm machines should be trained before allowed to handle any machine for farm operations.
... Therefore, the patterns and trends we observe over the past four decades in Denmark provide a partial picture of the cumulative human impact on local bird diversity -especially as the most significant land-use changes occurred long before (Finderup Nielsen et al. 2019). Delayed extinction debts may cause lagged biodiversity responses that can be missed even by national monitoring programs (Hanski and Ovaskainen 2002). Longer temporal analyses are therefore needed to capture true trajectories of biodiversity (Tingley and Beissinger 2013). ...
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Our understanding of how human activities impact biodiversity comes largely from space‐for‐time substitutions. However, spatial gradients are a poor surrogate for changes through time as they do not account for dynamic processes such as delayed extinction debts. Here we contribute towards filling this research gap by assessing the trajectories of local avian assemblages over 40+ years of climate and land‐use change. Using four decades of volunteer observations in Denmark we investigated long‐term trends of local bird richness, community structure, function, abundance, and biomass to better understand their anthropogenic drivers. Between 1976 and 2020, volunteers recorded ~ 2.4 million birds at 378 routes spanning a median of 15 years (range: 10–44). At the local level, we found a restructuring of bird communities over time (6% change per decade) and declines in abundance (−7% per decade), but stability in biomass, functional diversity, and spatial turnover. Local species richness showed a shallow decline on average. These results provide evidence that temporal turnover and loss of individuals are the most prominent features of recent ecological change in these communities. We found that the rate of local warming was positively associated with trends of species richness and functional diversity, suggesting a potential redistribution of warm‐adapted species. Meanwhile, communities that were becoming more spatially homogenous were associated with urban and farmland areas. In space, environmental changes are often distinct and recognisable, e.g. between forest and farmland. Through time, however, changes can be infrequent, gradual, and non‐linear. Despite these challenges, our results illustrate the power of spatially replicated, long‐term biodiversity monitoring programs for detecting the trends and attributing drivers of local biodiversity change.
... The long-term persistence of biodiversity in fragmented landscapes also depends on both the size of remnant habitat patches-which should be large enough to sustain viable populations-and their proximity, facilitating the movement of individuals between patches (MacArthur & Wilson 1963, 1967Chase et al. 2020). This connectivity is crucial for rescuing small populations, recolonizing locally extinct patches, and allowing different species to function as metapopulations (Hanski & Ovaskainen 2002). ...
Article
The influence of fragmentation per se on biodiversity is hotly debated, with evidence of negative, neutral, or even positive effects after controlling for habitat amount. Principles from this debate are often used to inform biodiversity conservation in remnant habitat fragments but are rarely considered in a restoration context. Habitat restoration is essential to work alongside conservation and reverse biodiversity declines. Although restored habitats vary along a similar fragmentation gradient to remnant patches, the importance of different processes likely varies. Communities in remnant patches are largely determined by existing populations, while communities in restored patches are shaped by colonization from nearby populations. We illustrate how fragmentation per se can have variable outcomes for biodiversity depending on whether habitat is conserved or restored. The fragmentation debate, in its current form, has limited application for restoration ecology, and we emphasize the need for ecologists and conservationists to consider the directionality of the fragmentation process.
... Ignoring potential extinction debts can lead to wrong directions 520 in biodiversity management (Hanski and Ovaskainen, 2002). In 521 our case, recognising the slow reaction of AM fungal diversity to 522 habitat loss due to agriculture can lead to better management of This preprint research paper has not been peer reviewed. ...
... Community biodiversity does not always respond in the immediate aftermath of environmental shifts (Hanski & Ovaskainen, 2002;Kuussaari et al., 2009;Vellend et al., 2006), thus suggesting that communities are often not in equilibrium with their current environment but rather with past conditions (e.g. Guo et al., 2020;Rowan et al., 2016;Sandel et al., 2020). ...
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Biodiversity is temporally dynamic, reflecting historical environmental conditions and influencing ecosystem stability. Colonisation and extinction dynamics frequently exhibit asynchronous patterns, resulting in net imbalances and thus to long‐lasting richness trends. If these trends are not functionally random, functional net imbalances between colonisations and extinctions (fNICE) are likely to emerge. Using community time series data of European freshwater fish and North American breeding birds, we investigated how fNICE differs from its taxonomic equivalent (tNICE), to provide a comprehensive picture of biodiversity dynamics. Our findings reveal that taxonomic and functional delays are a prevalent feature, challenging the assumption of an immediate response to environmental changes. Taxonomic delays manifest as extinction debts and colonisation credits, while functional delays indicate a shift in the balance between functional gains and losses over time. Moreover, we found that taxonomic and functional imbalances are not always directly correlated, although some specific patterns were found consistently for fish and birds. Early colonisations outpaced functional gains, indicating that although new species arrived earlier than the extinction of other species, the acquisition of new functional traits lagged. Although this may temporarily stabilise communities, as functional redundancy can mitigate loss of function via local extinctions, excessive redundancy can compromise biodiversity's capacity to respond to environmental variations, thereby undermining long‐term resilience. In conclusion, understanding the intricate temporal dynamics of biodiversity responses is paramount for effective conservation practices. While short‐term observations may suggest an equilibrium between diversity and the environmental conditions, our results underscore the importance of considering long‐term dynamics and the interplay between species traits and changing environments. The metrics tNICE and fNICE are valuable tools for quantifying these temporal dynamics and unravelling their consequences for ecosystem stability. Incorporating these insights into conservation strategies can aid in proactively preserving biodiversity and safeguarding the integrity of ecosystems. Read the free Plain Language Summary for this article on the Journal blog.
... Changes in the topography, depletion of natural resources, and urbanization have always been associated with human activity (Khaleghi, 2017). The connectedness between biological relationships with other nearby places might be broken by habitat loss (Hanski and Ovaskainen, 2002). Previous studies also reported that anthropogenic activities have significantly affected the natural environment (Goudie, 2013). ...
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The tropical dry forests (TDF) have an enormously rich flora and fauna that offer various ecological services to the surrounding human societies. Biodiversity assessment is mandatory for implementing any sustainable forest management policy, which is why it is one of the important criteria and indicators currently used. Threats to TDF biodiversity are the primary challenges arising from environmental concerns caused by anthropogenic activity leading to global warming issues. The study aimed to investigate the vegetation assessment and several environmental and anthropogenic variables influencing forest biodiversity from 5 threatened forest sites of District Sialkot (Ghalotian, Kishan Garh, Daburgi Chanda Singh, Pir Kot, and Ghulab Garh), Pakistan. We collected 170 distinct plant species, including 135 dicots, 27 monocots, seven pteridophytes, and one bryophyte, categorized into 138 genera and 62 families, divided into 114 herbs, 32 trees, and 24 shrubs. The phytosociological analysis described the quantitative characteristics, including % frequency, % density, % cover, and importance Value Index (IVI) of all forest areas. Gulab Garh forest has the richest biodiversity forest area, and herbs are the dominant species that have been documented. Environmental factors such as temperature, precipitation, organic matter, soil pH, Ca+2, Mg+2, Na+, Cl−, and electric conductivity (EC) strongly affect forest vegetation investigated by principal coordinate analysis. Shannon and Simpson’s diversity indexes reveal that all sites contain loamy and sandy soil and display a significant relationship between alpha diversity and richness. Increasing trends in temperature and decreasing trends in rainfall suggested that climate significantly affects the Sialkot region’s plant biodiversity. SWOT analysis highlighted that population growth leads to increasing anthropogenic activities such as constructing housing societies and roads, inadequate farming, and excessive grazing, impacting the forest vegetation and altering TDF ecosystem properties/services and functioning. Our findings reinforce the vegetational assessment and importance of local forest biodiversity and significant environmental drivers that influence the plant species diversity in TDF areas. Future conservation strategies are suggested to reduce unlawful resource consumption, restore plant biodiversity in designated protected areas, and conserve rare species locally.
... A large number of invasive plant removal experiments have been short term, involved only a few species in small plots and have been conducted mainly in grassland and herbaceous communities (Kettenring and Adams, 2011 and citations herein). Long-term data are essential for providing a baseline to evaluate the effects of disturbance and climate change effects on community structure and function because they allow enough time for the effects of species interactions to play out (Hanski and Ovaskainen, 2002;Lindenmayer et al., 2012). ...
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Island forests are becoming increasingly fragmented and colonized by invasive species, which can eventually lead to local species extinctions. In the Galapagos Islands, invasive species pose a serious extinction threat to the endemic daisy tree Scalesia pedunculata, formerly the dominant habitat-forming species of the unique Scalesia forest. This forest has been reduced to fragments due to land use changes in the past and is now increasingly invaded by introduced plants. We conducted a field experiment on Santa Cruz Island to assess the impacts of blackberry (Rubus niveus) and two other invasive plant species, Cestrum auriculatum and Tradescantia fluminensis, as well as the effects of the removal of two of these (R. niveus and C. auriculatum) on cover, composition and diversity of the resident plant communities. Particular attention was paid to effects of the invasive species on the S. pedunculata population. Annual vegetation monitoring was carried out in a total of 34 permanent plots (10 m × 10 m) over 10 years (2014-2023), using the line-intercept method. Seventeen of these plots were established in an invaded area and 17 plots in an area with continuous invasive plant removal since 2014. Results indicated that there were significant changes in both the species composition of the plant communities and average percent cover of species over time, comparing removal plots with invaded plots. Species composition in removal plots changed significantly more than in invaded plots, towards a plant community with greater percent cover of endemic species. A significant negative relationship between the three invasive species and cover of S. pedunculata suggested that multiple invader species may have additive negative impacts. Natural recruitment of S. pedunculata by seeds was observed in the removal but not in the invaded plots. These results, as well as the striking decrease of 71% in cover of adult S. pedunculata in the invaded plots indicate that this threatened species will be driven to local extinction on Santa Cruz Island, Galapagos, in less than 20 years if invasive plant species are not removed on a large scale.
... The observed increase in tolerance of threatened species (Appendix S2, Figure S9) may have ecological relevance in the form of extinction debt (Hanski & Ovaskainen, 2002). When using the maximum and the conservative human tolerance indices, one should be aware of the uncertainty stemming from the current extinction debt experienced by species in poor-quality habitats. ...
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Aim Some species thrive in human‐dominated environments, while others are highly sensitive to all human pressures. However, standardized estimates of species' tolerances to human pressures are lacking at large spatial extents and taxonomic breadth. Here, we quantify the world's bird species' tolerances to human pressures. The associated precision values can be applied to scientific research and conservation. Location Global. Time Period 2013–2021. Major Taxa Studied 6094 bird species. Methods We used binary observation data from eBird and modelled species' occurrences as a function of the Human Footprint Index (HFI). With these models, we predicted how likely each species was to occur under different levels of human pressures. Then, we calculated each species' Human Tolerance Index (HTI) as the level of the HFI where predicted occurrence probability was reduced to 50% of the maximum species' occurrence probability. We used resampling to obtain estimates of uncertainty of the Human Tolerance Indices. We also compared tolerances across species with increasing, stable, and decreasing population trends. Results We found that 22% of the bird species tolerated the most modified human‐dominated environments, whereas 0.001% of species only occurred in the intact environments. We also found that HTI varied according to species' population trend categories, whereby species with decreasing population trends had a lower tolerance than species with increasing or stable population trends. Main Conclusions The estimated HTI indicates the potential of species to exist in a landscape of intensifying human pressures. It can identify species unable to tolerate these environments and inform subsequent conservation efforts. We found evidence that species' sensitivity to human‐dominated environments may be driving birds' use of space. Bird species' tolerances are also linked to their population trends, making the tolerances a relevant addition to conservation planning.
... If the differences in species richness reported here do not represent global extinctions, but rather are instead merely local extirpations, then it suggests that these species have not been able to recolonize primary vegetation since. A potential mechanism may be that remnant patches of primary vegetation are too small or too isolated for successful colonization and persistence, such that areas of long human habitation have more fully paid the extinction debt incurred by initial human impacts (42,43). Without sub-fossils or fortuitously preserved specimens, determining whether these less diverse areas are a result of true extinctions is difficult. ...
Preprint
Habitat modification is responsible for substantial biodiversity declines, but communities vary in their tolerance to land-use change. One infrequently queried possibility is that historical factors determine the sensitivity of contemporary communities. We use bird community data from 54 studies across the world to test the hypothesis that pre-historic human presence reduced community sensitivity to land-use change by eliminating sensitive species in natural habitats. We find that pre-historic human population size correlates with reduced sensitivity of communities. Primary vegetation in areas with larger pre-historic human populations contain fewer species today, while species richness in structurally simple agriculture is unimpacted. The greatest signal of humans impacts dates back to 12,000 YBP suggesting that early humans may have caused even more widespread extinctions, than previously appreciated. One-Sentence Summary Areas with high human population 12,000 years ago have less biodiversity today, but are more tolerant of habitat modification
... Metapopulation extinction might thus lag the original landscape change (or other pressures) by decades; changes in the balance between extinction and recolonization might therefore become apparent only at a much later point in time. The original intervention causing the change in landscape capacity is thus triggering an "extinction debt" to be paid, possibly only after several years or decades (Fig. 3.1) (Hanski & Ovaskainen, 2002). The metapopulation perspective might be a suitable framework (1) to integrate the possible IDS root causes described above and (2) to date back the reasons for the currently observed decline rates to triggers of earlier times and (3) to explain a precipitous decline of individual and species numbers above a certain threshold of habitat destruction. ...
... We expect this is to become more and more evident at national level in the Netherlands as well. While populations may have lingered for some time under suboptimal climatic conditions, a phenomena often referred to as 'extinction debt' (Hanski and Ovaskainen 2002), the first losses are now becoming apparent. Besides C. hastulatum, other species which prefer cool conditions such as C. lunulatum, Aeshna juncea, Leucorrhinia rubicunda and Sympetrum danae (Termaat et al. 2019) are recently showing strong declines in the Netherlands as well (Van Grunsven et al. 2020). ...
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Given the rapid response of insects to environmental changes, their most prominent threats may change quickly as well. For effective insect species conservation it is therefore necessary to discriminate between former and current drivers of decline and to focus conservation efforts on the latter. We investigated how various environmental pressures, including former drivers of decline, have affected populations of the regionally endangered damselfly Coenagrion hastulatum and how their relevance has evolved over time. In our analysis, we compared water quality, vegetation properties and population trends across three distinct time spans: 1921–2000, 2001–2015 and 2016–2021. We included all known reproduction sites in the Netherlands, both current and historical, and also considered adjacent sites that were never inhabited. Ponds suitable for the species were characterised by mesotrophic conditions and high coverage of emergent and floating vegetation. Never inhabited ponds differed from inhabited ponds in being either more acidic or more eutrophic. Ponds where C. hastulatum disappeared between 2001 and 2015 had less of the mentioned vegetation structures and higher concentrations of various minerals. Ponds where the species disappeared after 2015 experienced severe droughts during 2018–2020. Most primary threats to C. hastulatum have shifted over time. In the past, changes in human use of ponds and increased sulphur and nitrogen deposition posed prominent threats. Presently, severe droughts, alongside nitrogen deposition have become the dominant concerns. Consequently, restoration of groundwater systems and rewetting measures are now first conservation priorities. Implications for insect conservation Our study highlights how threats to insect populations can rapidly evolve. Consequently, conservation strategies need regular evaluation and adjustment.
... Such analyses generally find that more biodiversity remains than would be predicted by species-area relationships (Figueiredo et al., 2019;Spalding and Hull, 2021;Montgomery et al., 2021). There seems to be an "extinction debt" (Hanski and Ovaskainen, 2002;Halley et al., 2016). Possibly there is a time lag between the eventual loss of these species and the actual loss of the last of its kind (Carroll et al., 2004;Kuussaari et al., 2009). ...
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Question: Can we best protect biodiversity from the loss of area set aside for nature by protecting the diversity of nature's evolutionary technologies (G-functions)? Premise: Efficiency and effectiveness in nature conservation are enhanced when appropriate ecological and evolutionary principles are brought to bear. The G-function framework sees species diversity as organized into sets of species that share a common fitness-generating function, or G-function. Within a G-function, evolution can be repeatable and reversible, whereas different G-functions possess non-repeatable and irreversible heritable traits. The family level of taxonomy may provide a good first cut at identifying different G-functions. Aims: Here, we explain the G-function framework and how species diversity can be organized into sets of species defined by repeatable versus non-repeatable heritable traits. We further discuss how preserving biodiversity within a G-function differs from that between G-functions and how this applies to ESS communities compared to non-ESS communities. ESS communities are tightly co-evolved, whereas non-ESS communities may arise from invasion structuring or human perturbations. Preserving the biodiversity of these two types of communities offers somewhat different challenges. Conclusions: The greatest evolutionary potential is retained when G-function diversity is maximized rather than species diversity per se. ESS communities are resistant to invasion by other species from within the same pool of G-functions and should represent the gold standard of conservation. An ESS community can only be invaded by species from G-functions alien to the community. Non-ESS communities require the most management effort and may require us to choose between naturalness of composition and naturalness of function. Behavioral indicators can be used to reveal mechanisms of species coexistence that emerge from the G-functions of a community and provide the practical tools for conserving these communities. Their mechanisms inform us about the ESS community that can emerge from it and reveal how far the community is from naturalness of function. Protecting biodiversity necessarily involves preventing extinctions, yet it seems that extinctions are lagging far behind what is expected from species-area relationships. Evolutionary Ecology Research, 2023: 45-64 Kotler et al. 46 This has been referred to as an extinction debt. The G-function framework suggests that some aspects of the extinction debt may be more apparent than real. Larger areas likely gave rise to more G-functions, but once evolved, G-functions and their constituent species can likely persist in much smaller areas. There is a favorable hysteresis. Consequently, with each G-function that we protect, we conserve both ecological and evolutionary potential. Thus, saving G-functions should be prioritized over haphazardly saving individual genera, species, or subspecies.
... In addition, we show that lichens on this substrate show a high beta diversity and that there is a nested pattern among deadwood qualities. This means that individual kelo wood substrates host unique species making them sensitive to anthropogenic and stochastic extinction (Hanski and Ovaskainen, 2002) and that deadwood lacking kelo-qualities only supports a subset of the deadwood-dependent lichen diversity found on kelo wood. Because we did not include natural forest in this study, we cannot evaluate if the higher beta diversity of kelo wood also occur in old-growth forests rich in natural structural elements or if this is a result of a continuous decrease of kelo wood in the landscape. ...
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Intensive forestry has led to landscape level deficits of important substrates such as deadwood and its associated biodiversity. Several taxa face extinction debts due to continuous declines and lack of regeneration of important habitats. Deadwood-dependent lichens are of great conservation concern due to a general lack of deadwood and due to their slow establishment, especially of rare species. In a field restoration experiment in central Sweden, we studied deadwood-dependent lichens for eight years, their association to different types of deadwood and their response to environmental change caused by variable retention forestry, deadwood enrichment and prescribed burning. Prescribed burning and site preparation caused depauperate lichen species assemblages throughout the study period but retention felling did not majorly affect lichen species assemblages. We found that lichen species were nested along deadwood qualities and deadwood created in the experiment only hosted a subset of lichen species found on kelo wood. Despite large reductions of kelo wood with lichen occurrences over the study period, overall species richness did not decrease. The fact that a large part of the lichen community occur only on kelo wood and that kelo wood is not regenerated implies that lichens associated with kelo wood face an extinction debt. In order to avoid local extinctions of deadwood-dependent lichens, site preparation and prescribed burning should be avoided in areas rich in high quality deadwood. There is urgent need to start creating new kelo wood through reoccurring fires in order to halt the impending extinction debt.
... However, intrinsic species traits (e.g., dispersal capacity, longevity, genetic plasticity), (meta)population dynamics (e.g., degree of connectivity), and species interactions can delay species disappearance. Thus, ecosystems tend to accumulate extinction debts during and after a perturbation (Hanski and Ovaskainen, 2002). As species go extinct, the "debt" is progressively paid off, and ecosystems shift toward a new equilibrium state. ...
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Near-time conservation palaeobiology uses palaeontological, archaeological and other geohistorical records to study the late Quaternary transition of the biosphere from its pristine past to its present-day, human-altered state. Given the scarcity of data on recent extinctions in the oceans, geohistorical records are critical for documenting human-driven extinctions and extinction threats in the marine realm. The historical perspective can provide two key insights. First, geohistorical records archive the state of pre-industrial oceans at local, regional and global scales, thus enabling the detection of recent extinctions and extirpations as well as shifts in species distribution, abundance, body size and ecosystem function. Second, we can untangle the contributions of natural and anthropogenic processes by documenting centennial-to-millennial changes in the composition and diversity of marine ecosystems before and after the onset of major human impacts. This long-term perspective identifies recently emerging patterns and processes that are unprecedented, thus allowing us to better assess human threats to marine biodiversity. Although global-scale extinctions are not well documented for brackish and marine invertebrates, geohistorical studies point to numerous extirpations, declines in ecosystem functions, increases in range fragmentation and dwindling abundance of previously widespread species, indicating that marine ecosystems are accumulating a human-driven extinction debt.
... Les documents cadres tels que l'instruction biodiversité de l'ONF (ONF, 2018), les recommandations au sein de plusieurs SRGS (Schéma Régional de Gestion Sylvicole) accompagnées de nombreux guides et initiatives de territoires pour la constitution d'une trame de « vieux bois » (ONF, 2017) vont dans le sens d'une amélioration. Toutefois, pour les espèces les plus exigeantes, la situation reste critique avec des populations le plus souvent extrêmement localisées dont la survie est remise en question par le temps nécessaire pour restaurer des conditions qui leur sont favorables (principe de la dette d'extinction, selon Hanski et Ovaskainen, 2002). Si les résultats d'évaluations montrent que la situation est globalement positive concernant l'évolution des populations d'oiseaux (Touroult et al., 2021), on observe un déclin des communautés d'arthropodes en forêt en terme de biomasse, d'abondance et de diversité, y compris sur des parcelles n'ayant pas subi de modification sur la période de suivi (Seibold et al., 2019). ...
... The decline in abundance and distribution of many insects has raised widespread public and political awareness on their biological value (Harvey et al. 2020;Didham et al. 2020;Wagner et al. 2021;Welti et al. 2021). As habitat loss and fragmentation have been identified as major drivers of this insect decline, a focus on connectivity conservation for (meta) population persistence is essential and justified (Hanski et al. 1996;Hanski and Ovaskainen 2002;Haddad et al. 2015;Cardoso et al. 2020). Connectivity is a biological concept, in which fluxes of individuals between patches in heterogenous landscapes are determined by both landscape configuration and the species' dispersal capacity. ...
Article
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Connectivity is a species- and landscape-specific measure that is key to species conservation in fragmented landscapes. However, information on connectivity is often lacking, especially for insects which are known to be severely declining. Patterns of gene flow constitute an indirect measure of functional landscape connectivity. We studied the population genetic structure of the rare digger wasp Bembix rostrata in coastal and inland regions in and near Belgium. The species is restricted to sandy pioneer vegetations for nesting and is well known for its philopatry as it does not easily colonize vacant habitat. It has markedly declined in the last century, especially in the inland region where open sand habitat has decreased in area and became highly fragmented. To assess within and between region connectivity, we used mating system independent population genetic methods suitable for haplodiploid species. We found more pronounced genetic structure in the small and isolated inland populations as compared to the well-connected coastal region. We also found a pattern of asymmetrical gene flow from coast to inland, including a few rare dispersal distances of potentially up to 200 to 300 km, based on assignment tests. We point to demography, wind and difference in dispersal capacities as possible underlying factors that can explain the discrepancy in connectivity and asymmetrical gene flow between the different regions. Overall, gene flow between existing populations appeared not highly restricted, especially at the coast. Therefore, to improve the conservation status of B. rostrata, the primary focus should be to preserve and create sufficient habitat for this species to increase the number and quality of (meta) populations, rather than focusing on landscape connectivity itself.
... La dette d'extinction fait d'abord référence au modèle initialement théorisé par Tilman et al. (1994) qui prédit l'extinction des espèces dans l'ordre de la plus compétitive à la moins compétitive après la disparition d'un habitat favorable, l'extinction d'une espèce pouvant intervenir plusieurs générations après la destruction. Par la suite, ce concept a été généralisé pour correspondre au temps nécessaire pour observer l'extinction d'une population après la destruction ou la fragmentation de son habitat (Loehle & Li 1996 ;Hanski & Ovaskainen 2002). Cette notion est particulièrement importante en biologie de la conservation puisqu'un milieu récemment dégradé présentera une richesse spécifique supérieure à sa richesse spécifique finale et son état écologique sera surévalué. ...
Thesis
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In France, the forest area decreased continuously until the middle of the 19th century, then increased rapidly following the industrial revolution. This forest minimum marks the limit between pre-existing "ancient forests" and the "recent forests" that were established later, because it makes it possible to assume a much longer forest continuity and to estimate precisely the historic forest areas thanks to the existence of complete historical maps (Napoleonic cadastre and Ordnance Survey maps among others). This temporal continuity of ancient forests induces a stability likely to favor the presence of particular species with low dispersal capacity and sensitive to disturbances.If the French forest area has almost doubled since 1850, it is estimated that 15 % of the forests present in 1840 has disappeared today at a national scale. Despite IUCN recommendations to protect ancient forests, conservation actions are still poorly defined and fall under the precautionary principle. This thesis project is part of a partnership with five French national parks located in mountain areas (Pyrenees, Cevennes, Mercantour, Ecrins and Vanoise) which have already vectorised and identified ancient forests on their territory. It aims to answer three main research questions :1- What is the role of ancient forests for the conservation of threatened species?2- Does the type of ancient land use influence the biodiversity of recent forests?3- Does forest management impact the biodiversity of ancient forests?The first question was addressed through statistical analysis of naturalist data collected by different networks of observers in the areas of adhesion of the five national parks in our study area. This work showed that threatened spermaphytes, pteridophytes, bryophytes, and forest beetles were more responsive to historical forest area than to current forest area, highlighting a 150-year lag in response to landscape change. The second part of the study was based on botanical surveys carried out in the forests of the Vanoise national park on four types of ancient use: forest, pasture, hay meadow and crop. This study showed that there was no difference in edaphic conditions between ancient forests and recent forests developed on former pastures and hay meadows, whereas forests located on former cropland had richer soils. On the other hand, differences in taxonomic and functional composition of understory plant communities were also smaller between ancient forests and former pastures than between ancient forests and former cropland. Finally, the third question was treated using metabarcoding surveys of fungal communities in the public forests of Vanoise with a gradient of time elapsed since the last harvest from one to 75 years. This study showed that the low-intensity silvicultural management of the Vanoise forests had little impact on soil fungal communities and confirmed the weak long-term traces left by grazing in recent forests.This work therefore highlights the importance of old-growth forests for the conservation of biodiversity, particularly forest species, but also emphasizes that the type of ancient land use is important to consider in recent forests. Former pastures in particular, which represent an important part of recent forests in mountain areas, have a lower impact than other land uses.
Article
This paper extends the θ\theta -logistic model to a more realistic nonautonomous framework that provides a wider perspective. This perspective grants all parameters the flexibility to vary with time. In this context, we show; from a mathematical point of view, the positivity and the continuation of solutions. In addition, we explore conditions under which the asymptotic behavior of the population density is in accordance with (or contrary to) that of time-varying carrying capacity. Accordingly, contributions are added to overcome the so-called Levins’ paradox and to clarify the case when extinction occurs even if the time-varying carrying capacity is unbounded. Some mathematical notions like origin attractivity and asymptotic stability are also discussed.
Preprint
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The ecosystem considered in this study is the outcome of a lengthy sequence of historical and ecological events. Patagonia's indigenous fauna comprises survivors of five significant extinction events, with the notable presence of the puma and the guanaco, two of the largest native mammals. In addition to these, European immigrants introduced sheep into the ecosystem. Together, these three species form a straightforward trophic network, featuring one predator and two prey species, all competing within the Patagonian steppe. For ranchers, guanacos and pumas are frequently perceived as threats to their economic interests. In recent decades, the field of biology, particularly ecology, has witnessed a substantial increase in the development of equation-based models. Scientists are interested in the ability to systematize hypotheses and gain insights into the behavior of complex biological systems, such as the one presented in this study. However, the nonlinear nature and the large number of parameters of models, represent a challenge when one wants to explore the parameter space. To overcome this and, at the same time, improve the understanding of the Patagonia ecosystem, we start by building an equation-based model based on previous contributions, and we reduce it to the essential minimum set of parameters. Then, we introduce two tools, a generalization of ternary graphs and a perceptron based ML, to help understand the response of the system equation to the key parameters. The perceptron tool allows us to visualize/interpret the influence of each parameter on the survival or extinction of each species. Through the generalization of the ternary graph, it was possible to conveniently visualize how the system responds to different combinations/variations of the five parameters of the reduced system equation in a single graphical representation.
Preprint
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Effective conservation of old-growth ecosystems, along with their unique biodiversity and climate benefits, requires coordinated actions from the scale of individual trees to broad regions. The US government is currently developing a conservation strategy for old-growth forest on federal lands, and similar efforts are occurring globally as nations implement the Kunming-Montreal Global Biodiversity Framework. An effective strategy must include elements at three spatiotemporal scales: immediate restrictions on harvest of old-growth and mature forests and old trees, standards to ensure management activities do not degrade old growth at the stand scale, and longer-term planning for old-growth restoration and recruitment across landscapes. Lessons from previous US forest policy, especially the Northwest Forest Plan, can inform efforts to strengthen each of these three components in the US old-growth conservation strategy. Ecosystem-based standards are needed to ensure protection of sufficient mature forest so that recruitment into the old-growth stage shifts ecosystems closer to historic proportions of old growth. In addition to clarifying existing goals related to ecological integrity, comprehensive old-growth policy must incorporate specific goals for recovering at-risk species based on empirical relationships across scales of biodiversity between forest habitat and species viability that are relevant across varied ecological contexts. Reversing extinction debt and ensuring long-term adaptation potential requires designation of large landscapes anchored by remaining old-growth stands, surrounded by areas managed for restoration of ecological integrity, native biodiversity, and ecosystem services including climate change mitigation.
Article
This article tracks changing conceptions of time in European forest science over recent decades, and accounts for how they can affect forest conservation and management. Through semiotic analysis of 62 peer-reviewed articles published in ecology and forestry, we (1) characterize the temporal features of old European forests as they evolve over our study period (1997–2017), and (2) trace how new and changing temporalities in forest science have reconfigured what constitutes a problem for conservationists and managers. We describe in particular how two articulations of forest time and forest management—Forest Continuity and Forest Maturity—have evolved, identifying the emergence of two new temporalities in old forest science. Over the study period, changing conceptions of forest pasts have increasingly led to consider forests as complex and evolving ecosystems from which humans cannot be excluded.
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This review provides an overview of the ethics of extinctions with a focus on the Western analytical environmental ethics literature. It thereby gives special attention to the possible philosophical grounds for Michael Soulé’s assertion that the untimely ‘extinction of populations and species is bad’. Illustrating such debates in environmental ethics, the guiding question for this review concerns why – or when – anthropogenic extinctions are bad or wrong, which also includes the question of when that might not be the case (i.e. which extinctions are even desirable). After providing an explanation of the disciplinary perspective taken (section “Introduction”), the concept of extinction and its history within that literature are introduced (section “Understanding extinction”). Then, in section “Why (or when) might anthropogenic extinctions be morally problematic?”, different reasons for why anthropogenic extinctions might be morally problematic are presented based on the loss of species’ value, harm to nonhuman individuals, the loss of valuable biological variety and duties to future generations. This section concludes by also considering cases where anthropogenic extinctions might be justified. Section “How to respond to extinctions?” then addresses a selection of topics concerning risks and de-extinction technologies. Finally, the section on “Extinction studies” introduces other viewpoints on the ethics of extinction from the extinction studies literature, followed by the “Conclusion”.
Article
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Informed population monitoring efforts are essential for sound management of harvested species, and adaptive strategies that provide detailed information to monitoring efforts often require data inputs from complimentary sources. Movement ecology information is seldom directly incorporated into population monitoring or adaptive harvest management strategies, yet can provide valuable information on species distributions, emigration and immigration rates, and aid in determining optimal population monitoring timing. The Rocky Mountain Population (RMP) of Sandhill Cranes is a harvested population subject to a stringent adaptive harvest management framework and an annual aerial survey to estimate population abundance, but movements of Sandhill Cranes during survey windows, and subsequent changes to harvest quotas based on their movement and distribution have not been investigated. We used seven years of GPS tracking data to estimate state-specific emigration and immigration rates, using a Bayesian multi-state capture-recapture model, among states within the RMP distribution to understand how seasonal crane movements may influence optimal aerial survey timing. We then leveraged these transition probabilities in conjunction with aerial survey count data to model how changes in aerial survey timing and movement-informed crane distribution would influence the current RMP Sandhill Crane adaptive harvest management model resulting in estimated changes to harvest allocation among states based on Sandhill Crane movement. We found that Sandhill Crane emigration from northern states began to increase the week of the aerial survey in late September, and continued to increase as autumn migration progressed into October. As expected, immigration to southern states began as emigration from northern states increased. Importantly, little movement among states occurred prior to the current aerial survey design timing. Overall, we found that current survey timing and shortly thereafter (~1 week) did not greatly influence estimates of Sandhill Crane distribution, and did not greatly influence the harvest reallocation to each state until mid to late October (range of -42–+52 tag allocation change), much later than the current survey design would allow. Using GPS locations, we found that optimal population monitoring efforts could be improved to account for both detection and seasonal movements, while minimally influencing current adaptive harvest management strategies to stakeholders. Linking movement ecology with population monitoring efforts and subsequently adaptive harvest management strategies yields insightful information that can be beneficial for conservation planning, decision-making, and optimal species management of a migratory bird.
Chapter
The increase in the world population is projected to reach 9.3 billion by the year 2050 and will no doubt require a significant and continued increase in food production to meet the food needs. The adoption of intensive agriculture began in the second half of the twentieth century and is dependent on diverse agrochemicals. Agricultural intensification practices involve the enlargement of small farms into large ventures, the concentration on the culture of single species of exotic cash crops, and the use of pesticides and fertilizers. The results from these practices have been very encouraging in terms of the amount of food produces but not without a price on biodiversity and environmental integrity. For instance, it has constituted a source of threat to wildlife habitats, niche functionality, and ecosystem processes and services all over the world with the outcome depending on the type and amount of agrochemical commonly used in the locale. This chapter attempts to collate evidence from previous studies on the extent of information on the detrimental effects of agricultural intensification through agrochemical use on the various environments and flora and fauna diversity around the world. The harmful effects of these modern agricultural practices are taking a negative toll on diverse important aspects of biodiversity and indirectly affecting human sustenance on Earth. To address this problematic trend, policies such as the adoption of sustainable agricultural practices are crucial. An example of such is organic agriculture which has less hazardous effects on biodiversity. These practices must be put in place by authorities and stakeholders in the agriculture industry so that food can be secured and conservation of biodiversity will be of major interest.KeywordsAgricultural intensificationAgrochemicalsBiodiversityEcosystemWildlife habitatsHabitat loss
Article
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Despite ongoing conservation efforts, pollinator biodiversity continues to decline at unprecedented rates. Conservation approaches tend to ignore landscape connectivity and focus mainly on increasing the availability of resources. Studies often find low or no effect of landscape connectivity on pollinator biodiversity. This may lead to a conclusion that pollinator assemblages are not sensitive to changes in landscape connectivity because pollinators are mobile species that can tolerate habitat fragmentation. However, the role of landscape connectivity might be underestimated, because of a failure to capture the effect on pollinator assemblages, undermining conservation efforts. Here we discuss evidence and theory indicating that the effects of landscape connectivity are underestimated due to a lack of consideration of the multiple aspects of biodiversity, including its spatial organization, community composition, functional diversity, species evenness, extinction debt and genetic diversity; and failure to measure aspects of landscape connectivity relevant to pollinators, namely spatial scale, matrix permeability, inter-habitat type connectivity and potential role of linear elements. Currently, available empirical evidence is scarce, thus, we suggest directions of further research and new conservation efforts to focus on maintaining aspects of landscape connectivity important to pollinators. Graphical abstract
Article
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This paper deals with patterns of biological diversity in Finnish forests and processes, both natural and human-caused, affecting this diversity.Ecologically relevant issues in relation to maintenance of biological deiversity, such as problems in measuring biodiversity, implications of ecological models, habitat fragmentation and systematic reverse selection are introduced.The work presents an overview of means of maintaining biological biological diversity in Finnish forests. Because it is impossible to maintain all the characteristics of natural forest landscape and forest structure in intensively managed forests, the foundation of nature reserves is of utmost importance.The present reserve network should be enlarged, and the minimum level should be at least 10 % of forest land protected in each biogeographic forest zone in a long term.Forest management practices should take into account the demands of sustaining biodiversity, such as preserving small scale key biotopes.In general, forestry should simulate natural dynamics of forests as much as possible.Effects of forest management on biota and adequacy in preserving biodiversity are essential future research priorities.
Article
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Reliable prediction of metapopulation persistence in fragmented landscapes has become a priority in conservation biology, with ongoing destruction of habitat confining increasing numbers of species into networks of small patches. A spatially realistic metapopulation model, which includes the first-order effects of patch area and isolation on extinction and colonization, has been tested. The distribution of an endangered butterfly was successfully predicted on the basis of parameter values estimated for a well-studied congeneric species. This modeling approach can be a practical tool in the study and conservation of species in highly fragmented landscapes.
Article
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HABITAT destruction is the major cause of species extinctions1–3. Dominant species often are considered to be free of this threat because they are abundant in the undisturbed fragments that remain after destruction. Here we describe a model that explains multispecies coexistence in patchy habitats4 and which predicts that their abundance may be fleeting. Even moderate habitat destruction is predicted to cause time-delayed but deterministic extinction of the dominant competitor in remnant patches. Further species are predicted to become extinct, in order from the best to the poorest competitors, as habitat destruction increases. More-over, the more fragmented a habitat already is, the greater is the number of extinctions caused by added destruction. Because such extinctions occur generations after fragmentation, they represent a debt—a future ecological cost of current habitat destruction.
Article
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Predicting species’ responses to habitat loss and fragmentation is one of the greatest challenges facing conservation biologists, particularly if extinction is a threshold phenomenon. Extinction thresholds are abrupt declines in the patch occupancy of a metapopulation across a narrow range of habitat loss. Metapopulation-type models have been used to predict extinction thresholds for endangered populations. These models often make simplifying assumptions about the distribution of habitat (random) and the search for suitable habitat sites (random dispersal). We relaxed these two assumptions in a modeling approach that combines a metapopulation model with neutral landscape models of fractal habitat distributions. Dispersal success for suitable, unoccupied sites was higher on fractal landscapes for nearest-neighbor dispersers (moving through adjacent cells of the landscape) than for dispersers searching at random (random distance and direction between steps) on random landscapes. Consequently, species either did not suffer extinction thresholds or extinction thresholds occurred later, at lower levels of habitat abundance, than predicted previously. The exception is for species with limited demographic potential, owing to low reproductive output , in which extinction thresholds occurred sooner than on random landscapes in all but the most clumped fractal landscapes . Furthermore, the threshold was more precipitous for these species. Many species of conservation concern have limited demographic potential, and these species may be at greater risk from habitat loss and fragmentation than previously suspected.
Article
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Tropical forests are becoming increasingly fragmented, threatening the survival of the species that depend on them. Small, isolated forest fragments will lose some of their original species. What is uncertain is how long this process of faunal relaxation will take. We compiled data on birds in five tropical forest fragments in Kakamega Forest, Kenya, of known date of isolation. We then predicted the original and eventual species richness of these fragments and, from this difference, the eventual species losses. Expressing the losses to date as a fraction of eventual losses suggests that faunal relaxation approximates an exponential decay with a half-life of approximately 50 years for fragments of roughly 1000 ha. In other words, in the first 50 years after isolation, tropical forest fragments of this size suffer half of the total number of extinctions that they are likely to experience. This result sets the time scale over which humanity must take conservation action in fragmented tropical forests, may aid efforts to set priorities, and indicates how high the future global extinction rate will be.
Article
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Habitat fragmentation is a potentially critical factor in determining population persistence. In this paper, we explore the effect of fragmentation when the fragmentation follows a fractal pattern. The habitat is divided into patches, each of which is suitable or unsuitable. Suitable patches are either occupied or unoccupied, and change state depending on rates of colonization and local extinction. We compare the behaviour of two models: a spatially implicit patch-occupancy (PO) model and a spatially explicit cellular automaton (CA) model. The PO model has two fixed points: extinction, and a stable equilibrium with a fixed proportion of occupied patches. Global extinction results when habitat destruction reduces the proportion of suitable patches below a critical threshold. The PO model successfully recreates the extinction patterns found in other models. We translated the PO model into a stochastic cellular automaton. Fractal arrangements of suitable and unsuitable patches were used to simulate habitat fragmentation. We found that: (i) a population on a fractal landscape can tolerate more habitat destruction than predicted by the patch-occupancy model, and (ii) the extinction threshold decreases as the fractal dimension of the landscape decreases. These effects cannot be seen in spatially implicit models. Landscape struc-ture plays a vital role in mediating the effects of habitat fragmentation on persistence.
Article
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A 20-yr study of a metapopulation of the American pika revealed a regional decline in occupancy in one part of a large network of habitat patches. We analyze the possible causes of this decline using a spatially realistic metapopulation model, the incidence function model. The pika metapopulation is the best-known mammalian example of a classical metapopulation with significant population turnover, and it satisfies closely the assumptions of the incidence function model, which was parameterized with data on patch occupancy. The model-predicted incidences of patch occupancy are consistent with observed incidences, and the model predicts well the observed turnover rate between four metapopulation censuses. According to model predictions, the part of the metapopulation where the decline has been observed is relatively unstable and prone to large oscillations in patch occupancy, whereas the other part of the metapopulation is predicted to be persistent. These results demonstrate how extinction-colonization dynamics may produce spatially correlated patterns of patch occupancy without any spatially correlated processes in local dynamics or extinction rate. The unstable part of the metapopulation gives an empirical example of multiple quasi equilibria in metapopulation dynamics. Phenomena similar to those observed here may cause fluctuations in species' range limits.
Article
The practical value of a predictive metapopulation model is much affected by the amount of data required for parameter estimation. Some metapopulation models require information on population turnover events for parameterization, whereas other models, such as the incidence function model that is used in this study, can be parameterized with spatial data on patch occupancy. The latter data are more readily available. The original method of using spatial pattern data to parameterize the incidence function and other patch models has been criticized for involving potentially troublesome assumptions, such as the independence of habitat patches and constant colonization probabilities. This study describes an improved parameter estimation method that is not affected by these problems. The proposed method is based on Monte Carlo inference for implicit statistical models, and it can be adapted to any stochastic patch occupancy model of metapopulation dynamics. As an additional advantage, the new method allows the estimation of the amplitude of regional stochasticity. Tested with simulated data, the new method was found to produce substantially more accurate parameter estimates than the original method. The new approach is applied to two empirical metapopulations, the false heath fritillary butterfly in Finland and the American pika at Bodie, California.
Book
Written by a world renowned biologist, this volume offers a comprehensive synthesis of current research in this rapidly expanding area of population biology. It covers both the essential theory and a wide range of empirical studies, including the author's groundbreaking work on the Glanville fritillary butterfly. It also includes practical applications to conservation biology. The book describes theoretical models for metapopulation dynamics in highly fragmented landscapes and emphasizes spatially realistic models. It presents the incidence function model and includes several detailed examples of its application. Accessible to advanced undergraduate and graduate students, Metapopulation Ecology will be a valuable resource for researchers in population biology, conservation biology, and landscape ecology.
Article
A basic demographic model is constructed for territorial species in a region where patches of habitat suitable for survival and reproduction are randomly (or evenly) interspersed with patches of unsuitable habitat. The model predicts the equilibrium occupancy of suitable habitat as a function of the proportion of the region composed of suitable habitat, h, and of the demographic potential of the population, k, which is determined by parameters of the life history and dispersal behavior of individuals. If 0 < k < 1, the demographic potential gives the equilibrium occupancy in a completely suitable region, and the population will become extinct in the region if h = or < 1 - k. Difficulty in finding a mate, the finite extent of the region containing suitable habitat, and serially uncorrelated fluctuations in life history parameters all increase the minimum value of h necessary to sustain a population. Models of this type should be useful for predicting the effects of habitat destruction and fragmentation, or habitat improvement, on the population sizes of rare or endangered species with territorial behavior.-Author
Article
Calassical demographic methods applied to life history data on the northern spotted owl yield and estimate of the annual geometric rate of increase for the population of λ=0.96±0.03, which is not significantly different from that for a stable population (λ=1.00). Sensitivity analysis indicates that adult annual survivorship has by far the largest influence on λ, followed by the probability that juveniles survive dispersal, and the adult annual fecundity. Substantial temporal fluctuations in demographic parameters have little effect on the long-run growth rate of the population because of the long adult life expectancy. A model of dispersal and territory occupancy that assumes demographic equilibrium is evaluated using data on the amount of old forest habitat remaining in the Pacific Northwest and the current occupancy of this habitat by northern spotted owls. This model is employed to predict the effect of future habitat loss and fragmentation on the population, implying that extinction will result if the old forest is reduced to less than a proportion 0.21±0.02 of the total area in a large region. The estimated minimum habitat requirement for the population is greater than that allowed in management plants by the USDA Forest Service.
Article
A study was made on the effects of recent landscape history on the subdivided populations of the carabid species Abax parallelepipedus in a hedgerow network. The distribution of this species on the site was strongly related to landscape connectivity. Occupied habitats are the least isolated from a source of colonizers. Connectivity measured as the distance to the nearest occupied site calculated along the hedgerow network and weighted by the quality of their wooded elements (WD) is a good predictor of the distribution of Abax parallelepipedus in the study area. Many landscape changes have occured between 1952 and 1993 both in the structure and the quality of the wooded network in this area. As a consequence, functional isolation between sample sites has increased by 28% since 1952. The results indicate that the current distribution of Abax parallelepipedus in the network is significantly better related to the 1952 landscape than to the current one. This may indicate the existence of a time lag between landscape changes and the reaction of Abax parallelepipedus to such modifications. The relationship remains the same over a broad range of spatial scales. This result should lead to the consideration of landscape history in species distribution analysis.
Article
Economically important pests usually attack a crop or group of crops over a wide region in which there are geographic, local, and temporal variations in the environment. Effectiveness of any control program will therefore depend on the different responses of the crop, pest, and control organism to this pattern of environment. Usually the environmental heterogeneity is treated as an unavoidable complication in program evaluation, and attempts are made to work with “average” conditions.
Article
1. This paper describes a novel approach to modelling of metapopulation dynamics. The model is constructed as a generalized incidence function, which describes how the fraction of occupied habitat patches depends on patch areas and isolations. 2. The model may be fitted to presence/absence data from a metapopulation at a dynamic equilibrium between extinctions and colonizations. 3. Using the estimated parameter values, transient dynamics and the equilibrium fraction of occupied patches in any system of habitat patches can be predicted. The significance of particular habitat patches for the long-term persistence of the metapopulation, for example, can also be evaluated. 4. The model is fitted to data from three butterfly metapopulations. The model predicts well the observed minimum patch size for occupancy and the numbers of extinctions and colonizations per year (turnover rate). The results suggest that local populations of the three butterflies in patches of 1 ha, which may support of the order of 1000 adult butterflies, have an expected lifetime of 20-100 years.
Article
We investigate the competition-colonization trade-off in a two-species competition model in various heterogeneous environments. The competitiveness of species is hierarchically ordered and the dynamics of the model are described by spatially local interactions of individuals. The size of the local neighborhood may depend on the species. The habitat consists of inhabitable and permanently destroyed sites. It was previously observed (Nee & May, 1992; Tilman et al., 1994, 1997) that destruction of habitat may aid the inferior species and cause the superior species to go extinct. These conclusions were based on an n-species model in which the spatial arrangement of destroyed sites was ignored. We examine the effects of different spatial arrangements of destroyed sites on survival and coexistence of the two species. We conclude that the spatial arrangement plays an important role and can influence the outcome qualitatively. The key quantity for predicting the outcome of habitat destruction on species survival is the relationship between the mean dispersal distance and the mean distance between inhabitable and destroyed sites. We contrast the hierarchical model with a version of the Lotka-Volterra model of interspecific competition and show that habitat destruction can alter the dominance relationship between species by reducing intraspecific competition.Copyright 1998 Academic Press
Article
Ecologists and conservation biologists have used many measures of landscape structure to predict the population dynamic consequences of habitat loss and fragmentation, but these measures are not well justified by population dynamic theory. Here we introduce a new measure for highly fragmented landscapes, termed the metapopulation capacity, which is rigorously derived from metapopulation theory and can easily be applied to real networks of habitat fragments with known areas and connectivities. Technically, metapopulation capacity is the leading eigenvalue of an appropriate 'landscape' matrix. A species is predicted to persist in a landscape if the metapopulation capacity of that landscape is greater than a threshold value determined by the properties of the species. Therefore, metapopulation capacity can conveniently be used to rank different landscapes in terms of their capacity to support viable metapopulations. We present an empirical example on multiple networks occupied by an endangered species of butterfly. Using this theory, we may also calculate how the metapopulation capacity is changed by removing habitat fragments from or adding new ones into specific spatial locations, or by changing their areas. The metapopulation capacity should find many applications in metapopulation ecology, landscape ecology and conservation biology.
Article
We model metapopulation dynamics in finite networks of discrete habitat patches with given areas and spatial locations. We define and analyze two simple and ecologically intuitive measures of the capacity of the habitat patch network to support a viable metapopulation. Metapopulation persistence capacity lambda(M) defines the threshold condition for long-term metapopulation persistence as lambda(M)>delta, where delta is defined by the extinction and colonization rate parameters of the focal species. Metapopulation invasion capacity lambda(I) sets the condition for successful invasion of an empty network from one small local population as lambda(I)>delta. The metapopulation capacities lambda(M) and lambda(I) are defined as the leading eigenvalue or a comparable quantity of an appropriate "landscape" matrix. Based on these definitions, we present a classification of a very general class of deterministic, continuous-time and discrete-time metapopulation models. Two specific models are analyzed in greater detail: a spatially realistic version of the continuous-time Levins model and the discrete-time incidence function model with propagule size-dependent colonization rate and a rescue effect. In both models we assume that the extinction rate increases with decreasing patch area and that the colonization rate increases with patch connectivity. In the spatially realistic Levins model, the two types of metapopulation capacities coincide, whereas the incidence function model possesses a strong Allee effect characterized by lambda(I)=0. For these two models, we show that the metapopulation capacities can be considered as simple sums of contributions from individual habitat patches, given by the elements of the leading eigenvector or comparable quantities. We may therefore assess the significance of particular habitat patches, including new patches that might be added to the network, for the metapopulation capacities of the network as a whole. We derive useful approximations for both the threshold conditions and the equilibrium states in the two models. The metapopulation capacities and the measures of the dynamic significance of particular patches can be calculated for real patch networks for applications in metapopulation ecology, landscape ecology, and conservation biology.
Article
Transient time in population dynamics refers to the time it takes for a population to return to population-dynamic equilibrium (or close to it) following a perturbation in the environment or in population size. Depending on the direction of the perturbation, transient time may either denote the time until extinction (or until the population has decreased to a lower equilibrium level), or the recovery time needed to reach a higher equilibrium level. In the metapopulation context, the length of the transient time is set by the interplay between population dynamics and landscape structure. Assuming a spatially realistic metapopulation model, we show that transient time is a product of four factors: the strength of the perturbation, the ratio between the metapopulation capacity of the landscape and a threshold value determined by the properties of the species, and the characteristic turnover rate of the species, adjusted by a factor depending on the structure of the habitat patch network. Transient time is longest following a large perturbation, for a species which is close to the threshold for persistence, for a species with slow turnover, and in a habitat patch network consisting of only a few dynamically important patches. We demonstrate that the essential behaviour of the n-dimensional spatially realistic Levins model is captured by the one-dimensional Levins model with appropriate parameter transformations.
Article
Simple analytical models assuming homogeneous space have been used to examine the effects of habitat loss and fragmentation on metapopulation size. The models predict an extinction threshold, a critical amount of suitable habitat below which the metapopulation goes deterministically extinct. The consequences of non-random loss of habitat for species with localized dispersal have been studied mainly numerically. In this paper, we present two analytical approaches to the study of habitat loss and its metapopulation dynamic consequences incorporating spatial correlation in both metapopulation dynamics as well as in the pattern of habitat destruction. One approach is based on a measure called metapopulation capacity, given by the dominant eigenvalue of a "landscape" matrix, which encapsulates the effects of landscape structure on population extinctions and colonizations. The other approach is based on pair approximation. These models allow us to examine analytically the effects of spatial structure in habitat loss on the equilibrium metapopulation size and the threshold condition for persistence. In contrast to the pair approximation based approaches, the metapopulation capacity based approach allows us to consider species with long as well as short dispersal range and landscapes with spatial correlation at different scales. The two methods make dissimilar assumptions, but the broad conclusions concerning the consequences of spatial correlation in the landscape structure are the same. Our results show that increasing correlation in the spatial arrangement of the remaining habitat increases patch occupancy, that this increase is more evident for species with short-range than long-range dispersal, and that to be most beneficial for metapopulation size, the range of spatial correlation in landscape structure should be at least a few times greater than the dispersal range of the species.
Article
When species diversity S on an island is displaced from the equilibrium value by injection or removal of species, S relaxes to equilibrium by an imbalance between immigration and extinction rates. Estimates of exponential relaxation times, t(r), for avifaunas of New Guinea satellite islands are calculated from analysis of four "experiments of nature": recolonization of exploded volcanoes, contraction in island area due to rising sea level, severing of land bridges, and disappearance of landbridge relict species. t(r) is in the range 3,000-18,000 years for avifaunas of islands of 50-3000 square miles (130-7800 km(2)), and increases with island area. Immigration coefficients decrease and extinction coefficients increase with increasing S. The results may be relevant to the design of rainforest preserves.
The red data book of Finland
  • P Rassi
Rassi, P. et al. 2001. The red data book of Finland. 3rd revision. Report. Ministry of Environment, Helsinki.
Understory birds and dynamic habitat mosaics in Amazonian rainforests Time lag between de-forestation and bird extinction in tropical forest fragments
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Terborgh, J., L. Lopez, J. Tello, D. Yu, and A. R. Bruni. 1997. Transitory states in relaxing ecosystems of land bridge islands. Pages 256–274 in W. L. Laurence and R. O. Bierregaard Jr., editors. Tropical forest remnants. University of Chicago Press, Chicago.
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