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Rarity or decline: Key concepts for the Red List of Australian eucalypts
Abstract
The 822 eucalypt species (Angophora, Corymbia, Eucalyptus) within Australia were assessed using IUCN Red List Categories and Criteria. Overall, 193 (23%) eucalypts qualified as threatened and 36 were considered Data Deficient. One hundred and thirty-four threatened species qualified under criterion A2, representing a past and irreversible population decline of>30%. The remainder were narrow-range species with ongoing threats (mostly mining or urbanisation), or naturally rare. Habitat conversion to crops and pastures was the cause of decline for most threatened eucalypts. Threatened species were concentrated where deforestation and high eucalypt richness coincide, especially south-western Western Australia. Corymbia or Angophora species, and relatively few tropical eucalypts are threatened. Fire, timber harvesting and disease were rarely sufficient threats to eucalypts to warrant a threatened status. Sheep grazing limits regeneration in temperate woodlands, but requires further quantification for individual species. Prior to this study, 89 eucalypts were listed as threatened under Australian environmental law. This assessment recommends that 32 of these species be downgraded to
Near Threatened or Least Concern. A further 11 species were identified as Data Deficient, while an additional 147 species were proposed for listing as threatened. This systematic assessment of Australian eucalypts emphasises the importance of decline rather than rarity when compared with previous listings, with broad implications for listing long-lived plants in deforested landscapes.
... Do spatial and biogeographic patterns of threatened and data-deficient flora reflect those of the flora as a whole, or are they associated with evolutionary history or threats, such as macro-scale levels of land transformation, which is a threat commonly cited as an overwhelming contributor to extinction risk [35,36]? 3. ...
... However, several of the geomorphological features supporting many conservation-listed flora retained high cover of native vegetation, illustrating a decoupling of conservation-listed flora occurrence from macro-scale levels of land transformation ( [20] cf. [35,36]). ...
... However, spatial patterns of occurrence of threatened and data-deficient Eucalyptus and Caladenia differ starkly from areas of greatest species richness in those genera overall. Eucalyptus species richness is greatest towards the southeastern coast [17,36]; yet, threatened and data-deficient Eucalyptus occurrence was greatest much further north in the Lesueur-Eneabba area. Although the reasons for these contrasting spatial patterns are not clear, intriguingly, several of the threatened Eucalyptus in the Lesueur-Eneabba area are hybrids [37]. ...
The Southwest Australian Floristic Region (SWAFR) supports an exceptional number of threatened and data-deficient flora. In this study, we: (i) collated statistics on the number, listing criteria and tenure of occurrence of threatened and data-deficient flora; (ii) conducted spatial and biogeographic analyses to address questions concerning patterns of diversity of threatened and data-deficient flora relative to the whole flora and evolutionary and threat drivers; and (iii) examined whether threatened and data-deficient flora richness is evenly distributed across plant lineages. We found that although threatened and data-deficient flora occurred across the breadth of the SWAFR, high richness was concentrated in a limited number of locations, which were not always strongly aligned with areas of higher land transformation. Data-deficient flora demonstrated different spatial patterns of occurrence to threatened flora. Approximately 70% of the populations of threatened and data-deficient flora occurred outside of lands managed primarily for conservation. Both evolutionary history and contemporary threats contribute to the current status and distribution of diversity of the threatened and data-deficient flora, with evolutionary history playing a significant role in predisposing a portion of the flora to having population traits that result in those flora meeting IUCN Red List criteria, along with ecological traits that predispose some to specific novel threats. An understanding of the distribution of species and threats, flora traits, and how these traits mediate susceptibility to threats, offers one potential way forward for an initial assessment of which of the 1819 data-deficient flora may be most at risk of extinction.
... The assumption that narrow-range endemics are threatened has come into question increasingly (Fensham et al., 2020). Being long lived, eucalypts often persist in very small populations for decades without obvious decline. ...
... Hence, narrow-range endemics that show such persistence without obvious threats are now being proposed for delisting as threatened taxa. Fensham et al. (2020) listed 59, not 74 (Barbour et al., 2010), narrow-range species as of conservation concern, most threatened by mining, urbanization or very low population numbers. ...
... Even resprouting mallees can be killed by two fires separated by a short interval of 1-3 years (Noble & Diggle, 2013). In contrast, tropical savanna eucalypts are fire tolerant and unresponsive to reductions in fire frequency and intensity (Fensham et al., 2020). Coping with fire is an attribute of most species. ...
OCBIL theory is a multi-hypothesis formulation aimed towards an understanding of the evolution, ecology and conservation of biological and cultural diversity on old, climatically buffered, infertile landscapes (OCBILs). OCBILs have been in existence contemporaneously with rainforest since Gondwanan times. Such landscapes are common in areas of eucalypt species richness embraced by Australia’s two Global Biodiversity Hotspots, the Southwest Australian Floristic Region and the Forests of East Australia. Here, I summarize evidence pertaining to the eucalypts in the context of a recent reformulation of OCBIL theory into 12 evolutionary, ecological and cultural hypotheses and ten conservation management hypotheses. A compelling argument emerges for a new interpretation of the eucalypts evolving out of the OCBILs, rather than out of the rainforests as traditionally interpreted. This calls for a significant reinterpretation of best conservation management of the eucalypts. For example, traditional ideas on application of fire in eucalypt communities regarded as well adapted to this disturbance need to give way to a more nuanced and cautious view. This review of eucalypts seen as evolving out of the OCBILs helps in understanding the group from several new perspectives. Interpretation of other sedentary plant and animal groups as out of the OCBILs is commended for further study.
... Formal assessment of a species' conservation status integrates the concepts of rarity and endangerment by considering both inherent demographic characteristics and perceived level of threat or evidence of population decline (Mace et al. 2008). A recent rapid assessment of the conservation status of eucalypts used International Union for Conservation of Nature (IUCN) Red Listing procedures (Fensham et al. 2020). One of the conclusions of the study was that more detailed assessments of some Eucalyptus species are required, particularly in the landscapes that have been cleared and where remnants are subject to intensive livestock grazing. ...
... The extent of population decline is determined over three generation lengths using IUCN criteria. Generation length is the average age of the parents of the current cohort (IUCN Standards and Petitions Committee 2019) and is assumed to be greater than 70 years for E. argophloia (Fensham et al. 2020). E. argophloia has a lignotuber, which confers some fire tolerance (Fensham et al. 2020). ...
... Generation length is the average age of the parents of the current cohort (IUCN Standards and Petitions Committee 2019) and is assumed to be greater than 70 years for E. argophloia (Fensham et al. 2020). E. argophloia has a lignotuber, which confers some fire tolerance (Fensham et al. 2020). ...
Eucalyptus argophloia is a species with a small geographic range occurring in a productive landscape with a subhumid climate. The past distribution of the species was assessed from remnant vegetation and standing paddock trees. The species grows in three specific vegetation types within its geographic range, and based on densities in remnant vegetation and reduction of habitat, it is estimated that the population has been reduced by 94.2%. There is very little regeneration of the species including on ungrazed roadsides, and further decline of the species is expected. The species can be categorised under IUCN Red Listing criteria as Critically Endangered. The present study provides a method for using habitat association, population decline and stand structure for conservation assessment of threatened tree species in productive landscapes.
... Large range-size species have been associated with instable climate and large habitat area whereas small range-size species are concentrated in stable heterogeneous climate and small habitat area (Morueta-Holme et al., 2013;Ohlemuller et al., 2008;Staude et al., 2020aStaude et al., , 2020b. Areas with large range sizes tend to harbor low density of large range-size species whereas areas with small range sizes tend to host high density of small range-size species but be vulnerable to environmental change (Fensham et al., 2020;Morueta-Holme et al., 2013). Therefore, determining the relationship between climatic and habitat characteristics and the distribution of rare and endangered plants is necessary to improve in situ conservation. ...
... over-exploitation or tourism), outside the region (e.g. farming or urban expansion), as well as low availability of breeding population (very small or restricted) (Fensham et al., 2020;Hui et al., 2020;IUCN, 2012;Swenson and Franklin, 2000). The medium-altitude mountains (1000-2000 m) have higher species density than the low-altitude mountains, which might be due to less human disturbances, rugged topography, and higher altitude, resulting in more stable habitat types (Fig. 2) (Liu et al., 2019). ...
Protecting rare and endangered plants is important for maintaining ecosystem structure and function, conserving biodiversity, and even sustaining national economic growth. However, the effects of habitat characteristics, geographical distribution, and climatic factors on the distribution of rare and endangered plants in China, home to 19.4 % of the world’s endangered species, remain unclear. To address this important knowledge gap, we collected information on climate, altitude, habitat, and distribution of rare and endangered plants in China to determine their habitat characteristics, geographical distribution, and the relationships between environmental factors and species density. We found that rare and endangered plants tend to occur in warm, humid, and forested habitats. Mountains, rather than plains, hills, eolian landforms, tablelands, lakes, and glaciers, can provide mesophytic and less-disturbed refuges for rare and endangered plants. In particular, medium and medium high-altitude mountains located in monsoon dominated regions with high precipitation, temperature, and humidity provide habitats for species of rare and endangered plants with high density. Our findings highlight the importance for a more explicit consideration of these mountains for in situ conservation of rare and endangered plants.
... There are 822 eucalypt species (Fensham et al., 2020), which dominate the forests and woodlands of coastal regions of Australia (except for mangroves and rainforests) and large areas of arid inland regions (Figure 1). The roots, trunks, and canopies of eucalypts do much to create the environment in which many other species of plants, fungi, vertebrates, and invertebrates exist (Williams & Woinarski, 1997). ...
... Freely accessible modern biodiversity databases, such as the Atlas of Living Australia (ALA; Belbin & Williams, 2016), support storage and analysis of species distributional data. The spatial portal of the ALA (Belbin, 2011) (Fensham et al., 2020) >455 species of many genera (Hoeksema & Cairns, 2019, Veron et al., 2019 With 14 exceptions eucalypt species are all endemic to Australia (Williams & Woinarski, 1997) Several endemic species (e.g., Wallace, Done, & Muir, 2012;Veron et al., 2019), but most also occur outside Australia 193 eucalypt species listed as threatened (IUCN Red List 2019.2) Many species listed as vulnerable (Carpenter et al., 2008, IUCN Red List 2017 Some growth rings, but can be problematic (Brookhouse, 2006) Some deposit growth rings that enable climate reconstruction (Lough & Cantin, 2014) Can live for hundreds of years (see Table 1.1. ...
Two of Australia's most iconic ecosystems have recently sustained heavy damage related to climatic changes: the extensive eucalypt forests from catastrophic bushfires and the Great Barrier Reef from mass coral bleaching. Despite obvious differences, eucalypt trees and reef corals share some similarities in biology and ecology, particularly in relation to climate change impacts and adaptation. Both groups are the focus of an increasing research effort to characterize and respond to climate changes and here we examine how sharing research experiences can benefit both fields. Four key areas of research are considered: (a) modeling current distributions, (b) assessing impacts of climate change on future distributions, (c) using human‐assisted migration to improve survival, and (d) applying genetic enhancement to improve the species’ survival. Examples of each research area are used to examine potential crossovers, limitations of the methods, and future requirements. We conclude that eucalypt and coral researchers, and indeed researchers for many other endangered taxa, can gain much by comparing experiences and methods, despite the apparent differences in their respective taxa.
This article is categorized under:
Assessing Impacts of Climate Change > Observed Impacts of Climate Change
... The genus Eucalyptus includes more than 750 species of flowering trees or mallees from the Myrtaceae family and along with other genera in the tribe Eucalypteae, including Angophora and Corymbia, are commonly known as 'eucalypts' (Coppen, 2002;Macphail & Thornhill, 2016). Eucalypts are predominantly native to Australia (except for Eucalyptus deglupta, the only species occurring naturally outside Australia in the Philippines, Indonesia and Papua New Guinea; Fensham et al., 2020) and, collectively, represent the most dominant group in the forests and woodlands of the continent (c. 40% of land area). ...
Aim
Eucalypts are important and popular urban tree species across cities worldwide. However, little is known about how their climatic niche breadth (CNB) and functional traits predict their success, and vulnerability, to current climate change in cities. We assessed the relationship between the CNB of eucalypts and key traits to understand their tolerance to climate change.
Location
Global urban areas, 66 cities in 21 countries.
Time period
1981 to 2022.
Major species studied
Fifty ‘eucalypt’ species belonging to the genera Eucalyptus , Angophora and Corymbia .
Methods
We used the species' safety margin concept to determine cities where eucalypts were planted outside the limits of their CNB, as defined from the native range, considering two extreme variables, maximum temperature of the warmest month (MTWM) and precipitation of the driest month (PDM). We assessed correlations between functional traits (leaf δ ¹³ C, leaf dry mass, leaf length, leaf N per dry mass, wood density) and negative safety margins, indicative of tolerance to non‐native conditions.
Results
In total, 42 species planted in 40 cities exceeded their safety margins for MTWM, while 43 species in 38 cities exceeded their safety margins for PDM. Within 24 cities, all species exceeded their native CNB for both MTWM and PDM. The cities of Atakpame (Togo), Chennai (India), Chongqing (China) and the US cities of Phoenix and Riverside had the highest richness of eucalypt species growing outside their native CNB. Broadly, species with wide CNB, small leaves, high δ ¹³ C, high leaf N per dry mass and high wood density were more likely to persist in cities where climatic conditions exceeded their native CNB.
Main conclusions
Eucalypts occupy many cities experiencing climatic conditions outside their native CNB. Species with traits characteristic of heat and drought tolerance are more often planted in cities where climatic conditions may exceed their CNB native limits.
... In this case, some experts and members of the public expressed concerns that periodic prescribed burning of the landscape would diminish the biodiversity and amenity values of the Peninsula. Prior to the establishment of the rural subdivision, a rotational prescribed burning program had been used to support grazing activities on the Peninsula, although grazing to reduce fire risk is a controversial strategy that has not always proven effective (Fensham et al. 2020). Ecological assessments indicated that this had allowed opportunistic native species such as peppermint and wattle to become dominant and weed species to thrive. ...
... Eucalypt is the general name of the species of genus Angophora, Corymbia, and Eucalyptus of the Myrtaceae family, containing a total of 945 species and varieties that are important economic species naturally distributed in countries such as Australia [1]. Known for their fast growth, high yield, strong adaptability, and wide-ranging applications, eucalyptus trees have been introduced to China for over a century. ...
Eucalyptus globulus is widely introduced and cultivated in Yunnan province. Its foliage is mainly used to extract eucalyptus oil, but the by-product eucalyptus residue has not been fully utilized. Based on the above reasons, in this study, we sought to explore the comprehensive utilization potential of eucalyptus resources. The total composition of eucalyptus residue was analyzed by ultra performance liquid chromatography-time-of-flight mass spectrometry (UPLC-Q/TOF MS), and the active components and nutrient components of eucalyptus leaf residue were determined by chemical methods and liquid phase techniques. Meanwhile, the antitumor activity of triterpenoids in eucalyptus leaves was evaluated by tetramethylazazole blue colorimetric assay (MTT). The results of qualitative analysis indicated that 55 compounds were identified from eucalyptus residue, including 28 phloroglucinols, 17 terpenoids, 3 flavonoids, 5 fatty acids, 1 amino acid and 2 polyphenols. Among them, the pentacyclic triterpenoids, in eucalyptus residue, were mainly oleanane type and urthane type. The results of quantitative determination indicated that the content of triterpenoid compounds was 2.84% in eucalyptus residue, which could be enhanced to 82% by silicone separation. The antitumor activity results showed that triterpenoid compounds have moderate inhibitory effects on human breast cancer cell MDA-MB-231, gastric adenocarcinoma cell SGC-7901 and cervical cancer cell Hela. The half maximal inhibitory concentration (IC50) was 50.67, 43.12 and 42.65 μg/mL, respectively. In this study, the triterpenoids from eucalyptus leaf residues were analyzed to reveal that the triterpenoids from eucalyptus leaf have antitumor effects and have potential to be developed as antitumor drugs.
... orchids) (Walsh et al. 2013;Bachman et al. 2019). In recent years, researchers have attempted to address these issues through systematic reevaluations of entire floras against IUCN Red List criteria, often with government funding (Silcock and Fensham 2018;Fensham et al. 2020). The IUCN have developed guidelines for applying the Red List categories and criteria at regional scales (IUCN 2012b) and have also coordinated large-scale regional Red List assessments across entire continents (Darwall et al. 2011). ...
Context
The International Union for Conservation of Nature (IUCN) Red List categories and criteria are a widely accepted standard for assessing extinction risk and have been adopted by many countries, including Australia. Tasmania is globally renowned for its biodiversity, and yet very few of its plant species have been evaluated using IUCN criteria, exposing a significant gap in conservation prioritisation.
Aims
This study aimed to undertake a regional IUCN assessment of Tasmania’s vascular flora and highlight gaps and discrepancies in accepted lists of threatened species.
Methods
The R package ConR was used to automatically generate preliminary IUCN assessments for 1885 taxa based on Criterion B (geographic range). This was compared to current listing status to identify potentially misaligned or at-risk taxa. Protected areas were incorporated into the analysis, and heatmaps were used to show the distribution of threatened flora in Tasmania based on their preliminary IUCN category.
Key results
One-third of Tasmania’s vascular flora (570 taxa) were categorised as threatened by ConR, of which only 47% are currently listed under legislation. We identify 301 non-listed taxa that are potentially threatened and can now be prioritised for full IUCN assessments. Taxa categorised as threatened are more likely to occur near cities and towns, often outside of formal protected areas.
Conclusion and implications
Automated IUCN assessments are a useful means of systematically refining lists of threatened species. The adoption of IUCN categories and criteria is likely to have a substantial effect on current lists of threatened species and could shift the focus of conservation efforts.
... As a consequence of the dramatic evolutionary diversification in OCBILs, rare and threatened species are accentuated in number (Fensham et al., 2020, Gosper et al., 2021. Thus, local endemism is pronounced globally on OCBILs. ...
OCBIL theory was introduced as a contribution towards understanding the evolution, ecology and conservation of the biological and cultural diversity of old, climatically buffered, infertile landscapes (OCBILs), especially in the Southern Hemisphere. The theory addresses some of the most intransigent environmental and cultural trends of our time – the ongoing decline of biodiversity and cultural diversity of First Nations. Here we reflect on OCBILs, the origins of the theory, and its principal hypotheses in biological, anthropological and conservation applications. The discovery that threatened plant species are concentrated in the Southwest Australian Floristic Region (SWAFR) on infertile, phosphorous-impoverished uplands within 500 km of the coast formed the foundational framework for OCBIL theory and led to the development of testable hypotheses that a growing literature is addressing. Currently, OCBILs are recognized in 15 Global Biodiversity Hotspots and eight other regions. The SWAFR, Greater Cape Floristic Region of South Africa and South America’s campos rupestres (montane grasslands) are those regions that have most comprehensively been investigated in the context of OCBIL theory. We summarize 12 evolutionary, ecological and cultural hypotheses and ten conservation-management hypotheses being investigated as recent contributions to the OCBIL literature.
... As a consequence of the dramatic evolutionary diversification in OCBILs, rare and threatened species are accentuated in number (Fensham et al., 2020, Gosper et al., 2021. Thus, local endemism is pronounced globally on OCBILs. ...
OCBIL theory was introduced as a contribution towards understanding the evolution, ecology and conservation of the biological and cultural diversity of old, climatically buffered, infertile landscapes (OCBILs), especially in the Southern Hemisphere. The theory addresses some of the most intransigent environmental and cultural trends of our time – the ongoing decline of biodiversity and cultural diversity of First Nations. Here we reflect on OCBILs, the origins of the theory, and its principal hypotheses in biological, anthropological and conservation applications. The discovery that threatened plant species are concentrated in the Southwest Australian Floristic Region (SWAFR) on infertile, phosphorousimpoverished uplands within 500 km of the coast formed the foundational framework for OCBIL theory and led to
the development of testable hypotheses that a growing literature is addressing. Currently, OCBILs are recognized in 15 Global Biodiversity Hotspots and eight other regions. The SWAFR, Greater Cape Floristic Region of South Africa and South America’s campos rupestres (montane grasslands) are those regions that have most comprehensively been investigated in the context of OCBIL theory. We summarize 12 evolutionary, ecological and cultural hypotheses and ten conservation-management hypotheses being investigated as recent contributions to the OCBIL literature
... Species not occurring in the local TDF of the study communities were not included in this comparison. (Fensham et al. 2020). Both species' threat status and usefulness are important criteria for selecting species in restoration efforts. ...
Forest restoration projects involving active planting should prioritize species that are useful to local communities, while also considering species' threat status and resistance to local stress factors, but scientific knowledge on these criteria is scarce, especially in understudied tropical ecosystems. We hypothesized that local ecological knowledge can help to fill this gap. Through interviews with 47 local experts and 197 randomly selected households in 8 rural communities of the tropical dry forests of northwestern Peru and southern Ecuador, we identified the species perceived as most useful, most threatened and most resistant to local stress factors. To better understand the studied local ecological knowledge, we also explored the following research questions and their implications for species selection decisions: (a) How does species' potential usefulness compare to their active use? (b) How does species' perceived threat status relate to their usefulness? (c) Does local knowledge on species' resistance to local stress factors corroborate scientific knowledge? We found large differences between the potential and active use of species and illustrate how data on both can yield useful insights. Further, we found that species' perceived threat status was mainly linked to their usefulness for construction wood, and that the vast majority of local perceptions on species' threat status and stress resistance coincided with scientific knowledge. Our findings illustrate the large potential of local ecological knowledge for improving species selection strategies and thereby increasing the success of forest restoration efforts worldwide.
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... Several range-restricted and endemic species have congeners that occupy extensive geographical ranges (e.g. eucalypts; Fensham et al. 2020), yet the reasons for such disparate differences in distribution for related taxa remain unclear. ...
Knowledge on how life history traits affect distribution in range-restricted and endemic plants is paramount for conservation and management, particularly for threatened species. Traits relating to dispersal ability are important in the ongoing persistence of range restricted species and may present a pathway to extinction or invasion. This is evident in the highly diverse and cosmopolitan genus Senecio (Asteraceae), where both threatened and invasive species occur within Australia. In this study, propagule geometry, settling velocity and dispersal potential for two range-restricted and threatened native taxa (S. linearifolious var. dangarensis Belcher ex I.Thomps., S. spathulatus var. attenuatus I.Thomps.) are contrasted with four native taxa that occupy wider ranges (S. amygdalifolius F.Muell., S. l. var. arachnoideus I.Thomps., S. l. var. macrodontus (DC.) I.Thomps., S. pinnatifolius A.Rich. var. pinnatifolius) and one introduced, wide-ranging species (S. madagascariensis Poir.). Differences were found in settling velocity and propagule morphology across all taxa. Based on propagule morphology, S. amygdalifolius has the greatest dispersal potential, S. spathulatus var. attenuatus the smallest, whereas all other taxa were similar. Although useful, dispersal potential alone does not fully explain distributional differences between all range-restricted and widespread taxa, and close assessment of habitat attributes may be required to further elucidate dispersal limitations in some taxa.
Trees play a vital role in ecosystems as they preserve biodiversity, contribute to primary productivity, and support ecological functions. From an economic perspective, humans derive significant benefits from trees. Multiple factors, including biotic and abiotic stresses, adversely affect tree species, leading to extensive tree mortality and consequently disrupting ecological balance. Abiotic stresses such as cold, salinity, and drought are projected to escalate due to global climate change, posing adverse consequences for tree populations. These effects may include biodiversity loss, disturbances in the carbon cycle, and a reduction in the services provided by trees. Trees have evolved a range of mechanisms, including biochemical, physiological and molecular strategies, to adjust to these stressors. Understanding abiotic stress-tolerance processes will enable constructive pyramiding of some tolerances in a single tree via genetic engineering. Furthermore, developing phenotyping technology broadens the range of features that may be assessed, providing us with a less ill knowledge of stress tolerance. A comprehensive understanding of these tolerance mechanisms is essential for developing artificial techniques to mitigate environmental stress. This book chapter highlights the major abiotic stresses in trees, their impacts, response mechanisms and strategies to mitigate these issues in trees.
Biodiversity is declining globally, yet many biodiversity hotspots still lack comprehensive species conservation assessments. Using multiple International Union for Conservation of Nature (IUCN) Red List criteria to evaluate extinction risks and millions of herbarium and forest inventory records, we present automated conservation assessments for all tree species of the Atlantic Forest biodiversity hotspot, including ~1100 heretofore unassessed species. About 65% of all species and 82% of endemic species are classified as threatened. We rediscovered five species classified as Extinct on the IUCN Red List and identified 13 endemics as possibly extinct. Uncertainties in species information had little influence on the assessments, but using fewer Red List criteria severely underestimated threat levels. We suggest that the conservation status of tropical forests worldwide is worse than previously reported.
Australia's biota is species rich, with high rates of endemism. This natural legacy has rapidly diminished since European colonization. The impacts of invasive species, habitat loss, altered fire regimes, and changed water flows are now compounded by climate change, particularly through extreme drought, heat, wildfire, and flooding. Extinction rates, already far exceeding the global average for mammals, are predicted to escalate across all taxa, and ecosystems are collapsing. These losses are symptomatic of shortcomings in resourcing, law, policy, and management. Informed by examples of advances in conservation practice from invasive species control, Indigenous land management, and citizen science, we describe interventions needed to enhance future resilience. Many characteristics of Australian biodiversity loss are globally relevant, with recovery requiring society to reframe its relationship with the environment.
In 1743, Georg Rumphius described a tree from the island of Seram in Herbarium Amboinense as Arbor Versicolor (now known as Eucalyptus deglupta Blume). Thus, the first European name for a species in the iconic Australian genus of Eucalyptus was coined decades before the British collected specimens in Australia, and before it was given its current name by a French botanist in 1789. The English translation of Rumphius’ description (see Supplementary Material) also includes vernacular names for Eucalyptus deglupta—some of many names applied to this species as it occurs from New Britain to Mindanao in the Philippines. While neither Rumphius’ name nor vernacular names for E. deglupta are recognised in current Western botanical nomenclature, the naming of Eucalyptus and other genera now recognised as Acacia, Casuarina and Melaleuca confirm the role of the eminent naturalist Rumphius in the history of Australian botany.
The use of criterion A of the IUCN Red List to categorize species as threatened that have undergone recent decline can lead to the listing of relatively common and widespread species. Loss of habitat through deforestation is a common cause of decline throughout much of the world but is often not incorporated into assessments because of uncertainty about the magnitude of change. A recent assessment of eucalypt species in Australia subject to deforestation provides a method for assessment under criterion A and has implications for listing of long-lived, widespread species affected by deforestation. Scenarios for two widespread eucalypt species subject to extensive deforestation are used to demonstrate how the threat status of a species may be recategorized in a lower threat category as declines resulting from a threatening process are mitigated. I argue that criterion A indicates an appropriate assessment of extinction risk and I provide a simple function based on predicted diminishment of the population decline to identify when a species could be disqualified from a threat category under subcriterion A2 (past decline).
Fire is a major disturbance driving the dynamics of the world's savannas. Almost all fires are set by humans who are increasingly altering fire timing and frequency on every continent. The world's largest protected areas of savannas are found in monsoonal northern Australia. These include relatively intact, tall, open forests where traditional indigenous fire regimes have been largely replaced in the past half century by contemporary patterns with trees experiencing fire as often as three out of five years. Eucalypt canopy trees form the basic structure of these savannas and changes to the canopy due to fire regimes cascade to affect other plants and animals. In this study, we used data from nearly three decades of field studies on the effects of fire on individual trees to define eight life‐history stages and to calculate transition rates among stages. We developed a stage‐based matrix population model that explicitly considers how fire season and understory influence growth, survival, and recruitment for each life‐history stage. Long‐term population growth rates and transient population dynamics were calculated under five different fire regimes, each in two understory types, using both deterministic and stochastic simulations of seasonal timing of fires. We found that fire was necessary for long‐term persistence of eucalypt canopy tree populations but, under annual fires, most populations did not survive. Population persistence was highly dependent on fire regime (fire season and frequency) and understory type. A stochastic model tended to yield higher population growth rates than the deterministic model with regular, periodic fires, even under the same long‐term frequency of fires. Transient population dynamics over 100 yr also depended on fire regime and understory, with implications for savanna physiognomy and management. Model predictions were tested in an independent data set from a 21‐yr longitudinal field study in Kakadu National Park. This study is a novel and integrative contribution to our understanding of fire in savanna biomes regarding the potential for long‐term persistence and transient dynamics of savanna canopy tree populations. The model is relatively simple, generalizable, and adaptable for further investigations of the population dynamics of savanna trees under fire.
The IUCN Red List criteria are a globally accepted method of assessing species extinction risk, and countries around the world are adapting these criteria for domestic use. First, we compared trends in IUCN Red List criteria used in threatened plant species listings in Australia and globally. Second, using the state of New South Wales (NSW), Australia, as a study region, we conducted two complementary analyses: (1) An assessment of ~ 5000 currently unlisted NSW plant species against the thresholds for the geographic range criterion (Criterion B) to identify species which may require full assessment; and (2) A rapid assessment of currently listed threatened plant species, applying the IUCN Red List Critically Endangered thresholds for all criteria, to identify species likely to be at the highest risk of extinction from further decline. Impacts on these species could be considered to be “serious and irreversible impacts” (SAII). Geographic range size was the most common criterion used in Australia and globally for plant listings. Our assessment of unlisted NSW plant species revealed 92 species (75 endemic to NSW) met the geographic range thresholds for Critically Endangered. Our rapid assessments of currently listed NSW threatened plant species identified 53.5% as having an extremely high risk of extinction should further decline occur. Of these, most were flagged under Criterion B (88.8%). Geographic range and the other IUCN Red List criteria thresholds for Critically Endangered provide a useful framework to identify species at an extremely high risk of extinction from ongoing decline.
Aim
Catastrophic forest mortality due to more extreme rainfall deficits and higher temperatures under future climate scenarios has been predicted. The aim of this study is to explore the magnitude of historical drought‐induced tree mortality under pre‐warming conditions.
Location
North‐eastern Australia.
Time period
1845–2017.
Major taxa studied
Trees.
Methods
Field survey, historical analysis and climate analysis.
Results
We present evidence of 18%–30% tree mortality from recent droughts across three regions of north‐eastern Australia with rainfall deficits less severe than earlier historical droughts. The corrected temperature record represents modest warming at the stations with long records in the vicinity of the study areas. In terms of rainfall deficit the most severe drought on record occurred in the early 20th century, and historical evidence confirms that this drought and earlier droughts before the advent of pastoralism coincided with substantial tree mortality.
Main conclusions
Dramatic declines in woody biomass in response to drought historically occurred more than once a century and are a natural phenomenon in semi‐arid Australia. The magnitude of drought‐induced tree mortality under natural climate fluctuations requires further investigation in other continents. Widespread drought‐induced tree mortality is not just a recent global change phenomenon and has been underestimated as a natural ecological process. However, even more severe forest die‐off events from more extreme hotter droughts are predicted if Earth’s warming proceeds as currently projected.
Inappropriate fire-regimes brought about by patterns of human settlement and land-use threaten plant diversity in Mediterranean-type climate (MTC) regions. In south-west Western Australia (SWWA), where there are many threatened plant species distributed across a range of human-modified landscapes, there is a need for approaches to identify where the threat is greatest. This requires knowledge of contemporary fire regimes, how they vary across landscapes, and the sensitivity of threatened species to these regimes. Currently, this information is lacking, and this limits strategic fire management. In this study we compiled fire response information for SWWA’s threatened plant species and undertook a bioregional assessment of variation in fire interval over the last 40 years. We determined the fire response traits of 242 (60%) of the region’s 401 extant threatened species. Over half of the 242 species were obligate seeders and will therefore have population dynamics particularly sensitive to fire interval. Our study highlights large differences in fire interval across nine bioregions in SWWA. The differences were greatest for the heavily cleared and fragmented bioregions compared with more continuously vegetated bioregions. We discuss how variations in the frequency of fire life-history traits and fire interval interact to determine the nature and relative level of threat posed by fire in these landscapes. Survival of many populations of threatened flora in this biodiversity hotspot will depend on developing appropriate fire regimes that match the regeneration requirements of each species.
Eucalyptus delegatensis R.T. Baker subsp. delegatensis is an interval-sensitive, fire-killed eucalypt that dominates large tracts of montane forest in the Australian Alps. Although it has been widely accepted in forest management that E. delegatensis takes 20 years to flower and fruit after stand-replacing fire events, recent observations after high intensity fires in the Australian Alps have shown that early flowering and fruiting is occurring from what can be termed ‘precocious’ individuals in some areas. In some instances, early flowering and fruit set is occurring within 6 years after stand-replacing fire. One historical study in the Australian Capital Territory had noted that such seed was viable, but we found no reported experiments documenting this or detailing the degree of viability. Here we discuss the results of a germination experiment undertaken on seed collected from Namadgi National Park from early-maturing alpine ash trees. Although at the low end of known viability estimates for E. delegatensis, seed from these individuals was nonetheless found to be viable, with a mean of 455 (s.d. = 139) germinants per 10 g of chaff and seed mix. We discuss this result in relation to fire management in the Australian Alps and suggest further research that needs to be undertaken to better document and understand the phenomenon.
Eucalypt species have several features that make them particularly well suited for climate change studies. A key assumption is that they have very limited powers of dispersal. If this is correct, it means that climate change analyses to the end of this century can concentrate mainly on assessing whether or not eucalypt species are likely to be able to survive at their existing sites. A recent major climate change study of more than 600 eucalypt species for the period 2014–2085 has used 5 km as a usual dispersal limit for the period to 2085, with the possibility of rare long-distance events. The review presented here considers how far natural stands of eucalypt species are likely to be able to migrate in the period to 2085. It is the first review to consider eucalypt seed dispersal as its major focus. It draws on evidence from millions of years ago to the present, and from eucalypt stands in Australia and around the world. Although rare long-distance events cannot be entirely ruled out, it is concluded that the great bulk of the evidence available indicates that the most likely potential dispersal rate is equivalent to about 1–2 m per year, i.e. ~70–140 m in the period to 2085. Over decades, this is likely to occur as a series of stepwise events, associated with disturbances such as bushfires. However, limitations such as inadequate remnant eucalypt stands and extensive agricultural developments may reduce actual migration rates below even this modest potential.
Rainfall, fire and competition are emphasized as determinants of the density and basal area of woody vegetation in savanna. The semi-arid savannas of Australia have substantial multi-year rainfall deficits and insufficient grass fuel to carry annual fire in contrast to the mesic savannas in more northern regions. This study investigates the influence of rainfall deficit and excess, fire and woody competition on the population dynamics of a dominant tree in a semi-arid savanna. All individuals of Eucalyptus melanophloia were mapped and monitored in three, 1-ha plots over an 8.5 year period encompassing wet and dry periods. The plots were unburnt, burnt once and burnt twice. A competition index incorporating the size and distance of neighbours to target individuals was determined. Supplementary studies examined seedling recruitment and the transition of juvenile trees into the sapling layer. Mortality of burnt seedlings was related to lignotuber area but the majority of seedlings are fire resistant within 12 months of germination. Most of the juveniles (≤1 cm dbh) of E. melanophloia either died in the dry period or persisted as juveniles throughout 8.5 years of monitoring. Mortality of juveniles was positively related to woody competition and was higher in the dry period than the wet period. The transition of juveniles to a larger size class occurred at extremely low rates, and a subsidiary study along a clearing boundary suggests release from woody competition allows transition into the sapling layer. From three fires the highest proportion of saplings (1–10 cm dbh) reduced to juveniles was only 5.6% suggesting rates of ‘top-kill’ of E. melanophloia as a result of fire are relatively low. Girth growth was enhanced in wet years, particularly for larger trees (>10 cm dbh), but all trees regardless of size or woody competition levels are vulnerable to drought-induced mortality. Overall the results suggest that variations in rainfall, especially drought-induced mortality, have a much stronger influence on the tree demographics of E. melanophloia in a semi-arid savanna of north-eastern Australia than fire.
This paper presents, for the first time, an overview of all known tree species by scientific name and country level distribution, and describes an online database—GlobalTreeSearch—that provides access to this information. Based on our comprehensive analysis of published data sources and expert input, the number of tree species currently known to science is 60,065, representing 20 percent of all angiosperm and gymnosperm plant species. Nearly half of all tree species (45%) are found in just ten families, with the three most tree-rich families being Leguminosae, Rubiaceae, and Myrtaceae. Geographically, Brazil, Colombia, and Indonesia are the countries with the most tree species. The countries with the most country-endemic tree species reflect broader plant diversity trends (Brazil, Australia, China) or islands where isolation has resulted in speciation (Madagascar, Papua New Guinea, Indonesia). Nearly 58 percent of all tree species are single country-endemics. Our intention is for GlobalTreeSearch to be used as a tool for monitoring and managing tree species diversity, forests, and carbon stocks on a global, regional, and/or national level. It will also be used as the basis of the Global Tree Assessment, which aims to assess the conservation status of all of the world’s tree species by 2020.
Australia’s terrestrial environment has been dramatically modified since European colonisation. Deforestation – the clearing and modification of native forest for agricultural, urban and industrial development – remains a significant threat to Australia’s biodiversity. Substantial policy reform over the last 40 years has delivered a range of policy instruments aimed to control deforestation across all Australian States and Territories. Despite these policy efforts – as well as strong governance and high institutional capacity – deforestation rates in Australia were nonetheless globally significant at the turn of this century. Legislation introduced in Queensland and New South Wales during the mid-2000s was at the time seen to have effectively ended broad-scale clearing; however, recent policy changes have raised concerns that Australia may again become a global hotspot for deforestation. Here, I describe the deforestation trends, drivers and policy responses in Australia over the last four decades. Using satellite imagery of forest cover and deforestation events across Australia between 1972 and 2014, I present a comprehensive analysis of deforestation rates at a fine resolution. I discuss trends in deforestation with reference to the institutional, macroeconomic and environmental conditions that are associated with human-induced forest loss in Australia. I provide a detailed history and critique of the native vegetation policies introduced across Australia over the last 40 years, including recent legislative amendments and reviews. Finally, I comment on future prospects for curbing deforestation in Australia, including the role of incentive-based policies such as carbon farming, private land conservation and biodiversity offsets. Despite being a highly active policy space, very little is known of the effectiveness of policy responses to deforestation in Australia, and whether the recent shift away from ‘command and control’ policies will necessarily lead to better outcomes. My analysis demonstrates the need for an effective policy mix to curb deforestation in Australia, including a greater focus on monitoring, evaluation and policy learning.
The identification of species at risk of extinction is a central goal of conservation. As the use of data compiled for IUCN Red List assessments expands, a number of misconceptions regarding the purpose, application and use of the IUCN Red List categories and criteria have arisen. We outline five such classes of misconception; the most consequential drive proposals for adapted versions of the criteria, rendering assessments among species incomparable. A key challenge for the future will be to recognize the point where understanding has developed so markedly that it is time for the next generation of the Red List criteria. We do not believe we are there yet but, recognizing the need for scrutiny and continued development of Red Listing, conclude by suggesting areas where additional research could be valuable in improving the understanding of extinction risk among species.
Background
Ocbil theory aims to develop hypotheses explaining the evolution and ecology of, and best conservation practices for, biota on very old, climatically buffered, infertile landscapes (Ocbils).
Scope
This paper reviews recent multi-disciplinary literature inspired by or reacting to aspects of Ocbil theory and discusses how it can assist conservation in biodiversity hotspots.
Conclusions
Ocbils occur in at least 12 out of 35 known terrestrial hotspots, but also in other biologically significant sites. Most evidence comes from the Southwest Australian and Greater Cape Floristic Regions, South America’s Pantepui, and the Campo Rupestre of Brazil, though predictions of the theory have been corroborated in 22 sites across South America, Western and Eastern Africa, Southern Asia, and Oceania. Most hypotheses have been corroborated, indicating that Ocbil theory has survived largely intact after 6 years of independent scientific critique, quantitative experimentation, and development. The theory also has been extended to allow identification and characterization of OCBISs (old, climatically-buffered, infertile seascapes), and OCFELs (old, climatically-buffered, fertile landscapes). We illustrate that the principles of Ocbil theory are key to conservation of biodiversity at global scale and provide new directions for research that can improve the theoretical and practical contributions of Ocbil theory.
Understanding the genetic basis of adaptation to contemporary environments is fundamental to predicting the evolutionary responses of tree species to future climates. Using seedlings grown in a glasshouse from 275 open-pollinated families collected from 37 Tasmanian populations, we studied quantitative genetic variation and adaptation in Eucalyptus pauciflora, a species that is widespread in Tasmania and the alpine regions of mainland Australia. Most traits exhibited significant quantitative genetic variation both within and between populations. While there was little association of the trait-derived Mahalanobis distance among populations with geographic distance or divergence in putatively neutral markers (FST), there was strong evidence of climate adaptation for several genetically independent, functional traits associated with ontogenetic maturation, biomass allocation, and biotic interactions. This evidence comprised the following: (i) significantly more differentiation among populations (QST) than expected through drift (FST); (ii) little association of pairwise population divergence due to drift (FST) and trait divergence (QST); and (iii) strong correlations of functional traits with QST > FST with potential environmental drivers of population divergence. Correlates with population divergence in quantitative traits include altitude and associated climatic factors, especially maximum temperature of the warmest period and moisture indices. It is argued that small changes in climate, such as a long-term 1 °C increase in the maximum temperature of the warmest period, are likely to affect the adaptation of local populations of the species. However, since there appears to be significant quantitative genetic variation within populations for many key adaptive traits, we argue that populations are likely to maintain significant evolutionary potential.
Plants provide fundamental support systems for life on Earth and are the basis for all terrestrial ecosystems; a decline in plant diversity will be detrimental to all other groups of organisms including humans. Decline in plant diversity has been hard to quantify, due to the huge numbers of known and yet to be discovered species and the lack of an adequate baseline assessment of extinction risk against which to track changes. The biodiversity of many remote parts of the world remains poorly known, and the rate of new assessments of extinction risk for individual plant species approximates the rate at which new plant species are described. Thus the question 'How threatened are plants?' is still very difficult to answer accurately. While completing assessments for each species of plant remains a distant prospect, by assessing a randomly selected sample of species the Sampled Red List Index for Plants gives, for the first time, an accurate view of how threatened plants are across the world. It represents the first key phase of ongoing efforts to monitor the status of the world's plants. More than 20% of plant species assessed are threatened with extinction, and the habitat with the most threatened species is overwhelmingly tropical rain forest, where the greatest threat to plants is anthropogenic habitat conversion, for arable and livestock agriculture, and harvesting of natural resources. Gymnosperms (e.g. conifers and cycads) are the most threatened group, while a third of plant species included in this study have yet to receive an assessment or are so poorly known that we cannot yet ascertain whether they are threatened or not. This study provides a baseline assessment from which trends in the status of plant biodiversity can be measured and periodically reassessed.
Despite the fact that the most changes in lists of threatened species reflect changes in knowledge rather than changes in conservation status, the lists continue to provide social and legal mandates for conservation; they are used to report on the state of the environment and to guide the allocation of scarce resources. There is a substantial under-representation of non-vascular species in threatened plant lists, reflected in an absence of documented extinctions among fungi and algae. Turnover in the composition of extinct flora lists in Australia suggests that the lists of threatened species may not be sufficiently reliable to form the basis for reporting on the state of the environment. They are of limited use in distinguishing between levels of threat and may not be a reliable guide for the allocation of scarce conservation resources among plant species. Systems for listing threatened species create a feedback loop, responsive to the subjective preferences of scientists, largely unresponsive to underlying true threats, self-perpetuating and accentuating bias with each iteration. Other tools, including formal decision approaches and the acquisition of new kinds of data, are needed to fill the roles.
Lack of basic data to assess plant species against IUCN Red List criteria is a major impediment to assigning accurate conservation status throughout large areas of the world. Erroneous assessments will be most prevalent in vast poorly surveyed areas where herbarium collections are sparse. In arid environments, assessments are further confounded by extreme temporal variability and poor understanding of the nature and magnitude of threats. We systematically re-assess the conservation status of an arid-zone flora. The status of all 1781 vascular plant species occurring across 635 300 km² of inland eastern Australia was initially assessed through herbarium records and expert interviews. This process generated a list of apparently rare and potentially threatened species, which guided a targeted survey program over 4 years. Search effort and key data on populations of candidate species found were recorded and used to assess 91 species against IUCN criteria. One-third of species were widespread and abundant at least in certain seasons, but had been deemed rare due to sparse collections. The conservation status of 20, mostly newly recognised species from restricted habitats, was upgraded and 14 remained listed because of having restricted areas of occupancy. With the exception of 12 artesian spring species, continuing declines were documented for just six species. The criterion that allows for listing of species because of extreme fluctuations (in combination with restricted and fragmented populations) needs to be carefully interpreted in arid zones, where these fluctuations may be apparent rather than real, and may actually confer resilience to grazing for some species. Our approach facilitates robust conservation assessments across vast and poorly known arid regions, distinguishing species that have merely been lost in space and time from those that are at risk of extinction.
This paper reviews ideas on the relationship between the ecology of clades and their distribution. Ecological biogeography represents a tradition that dates back to ancient times. It assumes that the distribution of organisms is explained by factors of present environment, especially climate. In contrast, modern systematics, following its origins in the Renaissance, concluded with Darwin that ‘neither the similarity nor the dissimilarity of the inhabitants of various regions can be accounted for by their climatal and other physical conditions’. In many cases, species distribution models – ecological niche models – based on the current environment of a species (its environmental envelope) fail to predict the actual distribution of the species. In particular, they often over-predict distributions. In addition, a group's niche often varies in space and time. These results provide valuable evidence that Darwin was correct, and many ecologists now recognise that there is a problem with the niche theory of distribution. Current ecological processes explain distribution at smaller scales than do biogeographical and evolutionary processes, but the latter can lead to patterns that are much more local than do many ecologists have assumed. Biogeographical phenomena often occur at a much smaller scale than that of the Wallacean regions. In areas that have been subjected to marine inundation or intense tectonism, many centres of endemism are only tens of kilometres across. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●●, ●●–●●.
Processes allowing coexistence of trees and grasses in tropical savannas have long intrigued ecologists. Early theories focused on climatic controls, but a conceptual model has emerged suggesting that savanna trees are subject to a fire-mediated recruitment bottleneck, with frequent fires preventing recruitment of saplings into the tree layer and maintaining biomass well below its climate-determined upper bound. We propose that this conceptual model has been overemphasised in northern Australia, where tree abundance is more strongly controlled by water availability. The dominant trees, eucalypts, have a remarkable capacity to grow through the ‘fire trap’ to reach fire-resistant sizes. This fire tolerance makes eucalypts relatively unresponsive to management-imposed reductions in fire frequency and intensity. Other trees in these savannas are typically more fire sensitive and respond positively to such management. There are suggestions that savanna fire management could lead to increases in woody biomass, but we contend that if tree biomass is strongly limited by water availability, then potential increases in tree biomass are relatively limited, at least in relation to the dominant eucalypt component. There is potential to increase the biomass of the more fire-sensitive non-eucalypts, but the upper bound of non-eucalypt tree biomass in these eucalypt-dominated systems remains poorly understood.
A survey of regenerative strategies in the eucalypts, including lignotuber development, was undertaken by extensive field observations, seedling trials and trials of cultivated individuals over a 12-year period. Four broad regenerative strategies were identified, viz. obligate seeders, lignotuber sprouters, stem sprouters and combination sprouters. These four regenerative strategies are based on the ability to develop a lignotuber and the regeneration strategy after whole-crown destruction. These regenerative strategies do not wholly correspond to the tree, mallee, mallet, marlock and shrub habit categories commonly applied to eucalypts. The obligate seeders include many more terminal taxa than have been previously documented as mallet taxa, with 78 western obligate seeders (the ‘true’ mallets) and nine eastern obligate seeders listed herein. Obligate seeders do not possess a lignotuber and are killed by crown-destructive events, and as such are relatively short-lived in most natural environments. A further 16 taxa are also known to be non-lignotuberous, but these are capable of producing epicormic regrowth from the trunk following crown destruction and are defined as stem sprouters. The remaining two regenerative strategies include taxa that are both lignotuberous and able to regenerate vegetatively following disturbance events. The persistent and conjecturous mallet–marlock–moort distinction is rejected, this study showing it to be dependent on stand density. Data presented indicate no significant difference in germination time or maturation time between western obligate-seeder taxa and closely related sprouter taxa. The conservation status of obligate-seeder taxa is discussed. Nomenclatural issues regarding the taxonomic distinction between obligate-seeder and resprouter sister taxa are discussed. A census of regenerative strategies for all recognised eucalypt taxa is included as an accessory publication on the web.
The International Union for Conservation of Nature (IUCN) is currently discussing the development of a Red List of Ecosystems (RLE) that would mirror the categories and criteria used to assess the conservation status of species. The suggested scientific foundations for the Red List of Ecosystems (Keith et al. 2013) are being considered by IUCN for adoption as the backbone of the RLE. We identify conceptual and operational weaknesses in the draft RLE approach, the categories and criteria. While species are relatively well described units there is no consistent means to classify ecosystems for assessing conservation status. The proposed RLE is framed mostly around certain features of ecosystems such as broad vegetation or habitat types, and do not consider major global change drivers such as climate change. We discuss technical difficulties with the proposed concept of ecosystem collapse and suggest it is not analogous to species extinction. We highlight the lack of scientific basis for the criteria and thresholds proposed by the RLE, and question the need to adopt the structure of the Red List of Species for a RLE. We suggest that the proposed RLE is open to ambiguous interpretations and uncertain outcomes, and that its practicality and benefit for conservation should be carefully evaluated before final approval.This article is protected by copyright. All rights reserved.
Global climate change is already impacting species and ecosystems across the planet. Trees, although long-lived, are sensitive to changes in climate, including climate extremes. Shifts in tree species' distributions will influence biodiversity and ecosystem function at scales ranging from local to landscape; dry and hot regions will be especially vulnerable. The Australian continent has been especially susceptible to climate change with extreme heat waves, droughts, and flooding in recent years, and this climate trajectory is expected to continue. We sought to understand how climate change may impact Australian ecosystems by modeling distributional changes in eucalypt species, which dominate or codominate most forested ecosystems across Australia. We modeled a representative sample of Eucalyptus and Corymbia species (n = 108, or 14% of all species) using newly available Representative Concentration Pathway (RCP) scenarios developed for the 5th Assessment Report of the IPCC, and bioclimatic and substrate predictor variables. We compared current, 2025, 2055, and 2085 distributions. Overall, Eucalyptus and Corymbia species in the central desert and open woodland regions will be the most affected, losing 20% of their climate space under the mid-range climate scenario and twice that under the extreme scenario. The least affected species, in eastern Australia, are likely to lose 10% of their climate space under the mid-range climate scenario and twice that under the extreme scenario. Range shifts will be lateral as well as polewards, and these east–west transitions will be more significant, reflecting the strong influence of precipitation rather than temperature changes in subtropical and midlatitudes. These net losses, and the direction of shifts and contractions in range, suggest that many species in the eastern and southern seaboards will be pushed toward the continental limit and that large tracts of currently treed landscapes, especially in the continental interior, will change dramatically in terms of species composition and ecosystem structure.
Plant taxa can be broadly divided based on the mechanisms enabling persistence through whole-crown disturbances, specifically whether individuals resprout, populations reseed, or both or neither of these mechanisms are employed. At scales from species through to communities, the balance of disturbance-response types has major ramifications for ecological function and biodiversity conservation. In some lineages, morphologically identical populations except for differences in a disturbance-response trait (e.g. ± lignotuber) occur, offering the opportunity to apply genetic analyses to test whether trait state is representative of broader genetic distinctiveness, or alternatively, variation in response to local environmental conditions. In eucalypts, a globally-significant plant group, we apply dense taxon sampling and high-density, genome-wide markers to test monophyly and genetic divergence among pairs of essentially morphologically-identical taxa excepting lignotuber state. Taxa differing in lignotuber state formed discrete phylogenetic lineages. Obligate-seeders were monophyletic and strongly differentiated from each other and lignotuber-resprouters, but this was not the case for all lignotuber-resprouter taxa. One lignotuber state transition within our sample clade was supported, implying convergence of some non-lignotuber morphology characters. Greater evolutionary rate associated with the obligate-seeder disturbance-response strategy offers a plausible explanation for these genetic patterns. Lignotuber state is an important taxonomic character in eucalypts, with transitions in lignotuber state having contributed to the evolution of the exceptional diversity of eucalypts in south-western Australia. Differences in lignotuber state have evolved directionally with respect to environmental conditions.
A 2017 paper intended to assist climate-change studies concluded that provenances of the widely distributed Eucalyptus tereticornis ‘are not differentiated in their thermal responses’ in terms of photosynthesis, respiration and growth. The aim here was to place this surprising result, based on a short-term (48-day) experiment with seedlings of just three provenances, into the broader context of several years’ growth of provenances of the same species. To do this, a re-analysis of results from trials of 14 provenances of E. tereticornis was undertaken. These were grown for 3.5 or 5.0 years at four contrasting sites in southern China spanning mean annual temperatures (MAT) from 15.0°C to 23.5°C. The analysis described here compares MATs at climate-of-origin with volume growth. It demonstrates an approach that could easily be applied to provenance studies of other commercially important species. It makes use of the ready access to distributional and climatic data provided by a modern biodiversity database, the Atlas of Living Australia. Some of the provenances showed a surprising level of adaptability to climates markedly different to those of their origin. At the warmest site in China, however, the growth of the provenances was significantly related to the MAT at their climate-of-origin. It is concluded that researchers considering the likely impacts of climate change on tree species may find it useful to examine results from commercial provenance trials as well as from glasshouse experiments with seedlings.
Aim Comparative analyses of fire regimes at large geographical scales can potentially identify ecological and climatic controls of fire. Here we describe Australia’s broad fire regimes, and explore interrelationships and trade-offs between fire regime components. We postulate that fire regime patterns will be governed by trade-offs between moisture, productivity, fire frequency and fire intensity. Location Australia. Methods We reclassified a vegetation map of Australia, defining classes based on typical fuel and fire types. Classes were intersected with a climate classification to derive a map of ‘fire regime niches’. Using expert elicitation and a literature search, we validated each niche and characterized typical and extreme fire intensities and return intervals. Satellite-derived active fire detections were used to determine seasonal patterns of fire activity. Results Fire regime characteristics are closely related to the latitudinal gradient in summer monsoon activity. Frequent low-intensity fires occur in the monsoonal north, and infrequent, high-intensity fires in the temperate south, demonstrating a trade-off between frequency and intensity: that is, very high-intensity fires are only associated with very low-frequency fire regimes in the high biomass eucalypt forests of southern Australia. While these forests occasionally experience extremely intense fires (> 50,000 kW m⁻¹), such regimes are exceptional, with most of the continent dominated by grass fuels, typically burning with lower intensity (< 5000 kW m⁻¹). Main conclusions Australia’s fire regimes exhibit a coherent pattern of frequent, grass-fuelled fires in many differing vegetation types. While eucalypts are a quintessential Australian entity, their contribution as a dominant driver of high-intensity fire regimes, via their litter and bark fuels, is restricted to the forests of the continent’s southern and eastern extremities. Our analysis suggests that the foremost driver of fire regimes at the continental scale is not productivity, as postulated conceptually, but the latitudinal gradient in summer monsoon rainfall activity.
This paper examines progress made with species distribution modelling (SDM) for trees under climate change. Following brief background information, the main focus is on developments in the last five years. Correlative SDMs have become the most commonly used approach for analysing potential climate change impacts on areas suitable for particular species. The use of SDMs has been criticized, but responses to these criticisms are provided and limitations may not be as great as has been suggested. For many species SDMs are the only potential source of data for learning about likely climate change impacts, and suitable occurrence data for SDM analyses exist for about 50 000 tree species. SDM papers have already been published presenting analyses for more than 1000 tree species under projected climate change. Most SDM climate change analyses adopt an ‘equilibrium assumption’ that tree species natural distributions provide a reliable estimate of their climatic requirements. However, in addition to natural distribution data, data from trials outside their natural distributions are desirable to determine their intrinsic climatic adaptability. Progress is described in relation to climatic data, soil data, species distribution data, species and provenance trial data, descriptions of species climatic requirements, mapping of suitable areas and integration of species and environmental data. Desirable future objectives are identified for each of these topics.
Species‐level forecasts of distributional potential and likely distributional shifts, in the face of changing climates, have become popular in the literature in the past 20 years. Many refinements have been made to the methodology over the years, and the result has been an approach that considers multiple sources of variation in geographic predictions, and how that variation translates into both specific predictions and uncertainty in those predictions. Although numerous previous reviews and overviews of this field have pointed out a series of assumptions and caveats associated with the methodology, three aspects of the methodology have important impacts but have not been treated previously in detail. Here, we assess those three aspects: (1) effects of niche truncation on model transfers to future climate conditions, (2) effects of model selection procedures on future‐climate transfers of ecological niche models, and (3) relative contributions of several factors (replicate samples of point data, general circulation models, representative concentration pathways, and alternative model parameterizations) to overall variance in model outcomes. Overall, the view is one of caution: although resulting predictions are fascinating and attractive, this paradigm has pitfalls that may bias and limit confidence in niche model outputs as regards the implications of climate change for species’ geographic distributions. Species‐level forecasts of distributional potential and likely distributional shifts, in the face of changing climates, have become popular in the literature in the past 20 years. Here, we depict geographic dimensions of effects of (1) specific point occurrence data used, (2) representative concentration pathway, (3) general circulation model, and (4) parameter settings, as they affect future model transfer results.
Jarrah dieback was the name given to the sudden death of Eucalyptus marginata in the southwest of Western Australia, a serious economic problem. Although deaths were attributed to Phytophthora cinnamomi in the 1960s, the supporting evidence was weak; these deficiencies were not realised until 1980. Renewed interest in jarrah pathology showed that the incidence and severity of root lesions caused by P. cinnamomi in live trees was low, but in recent deaths it could be isolated from the root collar and large roots of some, but not all trees. Jarrah deaths result from hydraulic failure, implying extensive sapwood damage. This is unlikely to result from P. cinnamomi infection, which preferentially invades phloem, but could result from waterlogging, which causes tyloses to form in xylem vessels so they no longer conduct water. Tylosed root sapwood has been reported from investigations into jarrah deaths. An interpretation of past deaths based on stress factors better fits where and when deaths occur. This is within 3 years of exceptionally heavy rainfall, an inciting factor. Predisposing conditions are sites with some form of poor drainage, such as water-gaining sites, or those with impeded sub-soil drainage. Recent logging further increases site wetness. Phytophthora cinnamomi should be seen as a contributing factor, which is normally compartmentalised by the host, but can spread extensively in dying trees.
Models of vegetation dynamics framed as testable hypotheses provide powerful tools for predicting vegetation change in response to contemporary disturbances or climate change. Synthesizing existing information and applying new data, we develop a conceptual model of vegetation states and transitions for the previously overlooked woodlands dominated by obligate‐seeder eucalypts of dry to semi‐arid south‐western Australia. These comprise the largest extant temperate woodland globally, are uniquely dominated by a high diversity of obligate‐seeder eucalypts (55 taxa), but are under threat from wildfire. Our conceptual model incorporates four critical ecological processes that also distinguish obligate‐seeder woodlands from temperate woodlands dominated by resprouting eucalypts: (i) a lack of well‐protected epicormic buds results in major disturbances (prominently fire) being stand‐replacing. The pre‐disturbance tree cohort is killed, followed by dense post‐disturbance recruitment from seed shed from a serotinous seed bank; (ii) competition between saplings leads to self‐thinning over a multi‐century timeframe, with surviving individuals having great longevity (regularly >400 years); (iii) multiple processes limit recruitment in the absence of stand‐replacement disturbances, leading to frequent single‐cohort stands. However, unlike the few other obligate‐seeder eucalypt communities, trickle recruitment in very long‐unburnt stands can facilitate indefinite community persistence in the absence of stand‐replacement disturbances; and (iv) discontinuous fuels, relatively low understorey flammability (low grass and often high chenopod cover) and topographic barriers to fire (salt lakes) allow mature woodlands to persist for centuries without burning. Notably though, evidence suggests that flammability peaks at intermediate times since fire, establishing a ‘flammability bottleneck’ (or landscape fire trap) through which regenerating woodlands must pass. Our model provides a framework to support management to conserve obligate‐seeder eucalypt woodlands. Research into reasons for exceptional tree heights relative to ecosystem productivity, the evolution of diverse and dominant obligate‐seeder eucalypts, the paucity of grass, and the recent spatial distribution of fires, will further inform conservation management.
Myrtle rust (Austropuccinia psidii) is an invasive rust fungus that attacks species of the Myrtaceae family, one of
the most dominant plant families in Australia. The potential extent of myrtle rust affected areas and the high
number of potential host species make a species prioritisation scheme essential to direct conservation and
management efforts. This study builds on previous work by: compiling an up-to-date list of myrtle rust occurrences
and host species; mapping current and future climate suitability for myrtle rust; and identifying host
species at risk based on range overlaps and susceptibility data.
Suitable habitat for myrtle rust is restricted to eastern and southern coastal areas of Australia, with minor
areas in the Northern Territory and Western Australia. This coastal distribution remains present under future
climates, with some extension in inland New South Wales and Tasmania, and a reduction of suitable habitat in
northern Queensland and Western Australia. Contrary to previous studies, our results indicate that south-west
Western Australia has low climatic suitability for myrtle rust. Under current climate, 1285 Myrtaceae species are
at risk of exposure to myrtle rust. This number decreases to 1224 species under future climate.
We divide species exposed to myrtle rust into three priority categories, giving highest priority to species with
at least 70% of their range overlapping regions climatically suitable for myrtle rust under current or future
climates. We find 23 species are of high priority for conservation action. Finally, we provide a series of recommendations for management of species within each priority category.
One of the criteria used by the International Union for Conservation of Nature (IUCN) to assess threat status is the rate of decline in abundance over 3 generations or 10 years, whichever is longer. The traditional method for calculating generation length ( T ) uses age‐specific survival and fecundity, but these data are rarely available. Consequently, proxies that require less information are often used, which introduces potential biases. The IUCN recommends 2 proxies based on adult mortality rate, = α + 1/ d , and reproductive life span, = α + z * RL, where α is age at first reproduction, d is adult mortality rate, RL is reproductive life span, and z is a coefficient derived from data for comparable species. We used published life tables for 78 animal and plant populations to evaluate precision and bias of these proxies by comparing and with true generation length. Mean error rates in estimating T were 31% for and 20% for , but error rates for were 16% when we subtracted 1 year ( ), as suggested by theory; also provided largely unbiased estimates regardless of the true generation length. Performance of depends on compilation of detailed data for comparable species, but our results suggest taxonomy is not a reliable indicator of comparability. All 3 proxies depend heavily on a reliable estimate of age at first reproduction, as we illustrated with 2 test species. The relatively large mean errors for all proxies emphasized the importance of collecting the detailed life‐history information necessary to calculate true generation length. Unfortunately, publication of such data is less common than it was decades ago. We identified generic patterns of age‐specific change in vital rates that can be used to predict expected patterns of bias from applying .
Predicting the consequences of climate change for biodiversity is critical to conservation efforts. Extensive range losses have been predicted for thousands of individual species, but less is known about how climate change might impact whole clades and landscape-scale patterns of biodiversity. Here, we show that climate change scenarios imply significant changes in phylogenetic diversity and phylogenetic endemism at a continental scale in Australia using the hyper-diverse clade of eucalypts. We predict that within the next 60 years the vast majority of species distributions (91%) across Australia will shrink in size (on average by 51%) and shift south on the basis of projected suitable climatic space. Geographic areas currently with high phylogenetic diversity and endemism are predicted to change substantially in future climate scenarios. Approximately 90% of the current areas with concentrations of palaeo-endemism (that is, places with old evolutionary diversity) are predicted to disappear or shift their location. These findings show that climate change threatens whole clades of the phylogenetic tree, and that the outlined approach can be used to forecast areas of biodiversity losses and continental-scale impacts of climate change. © 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
Optimal foraging behaviour by nectavores is expected to result in a leptokurtic pollen dispersal distribution and predominantly near-neighbour mating. However, complex social interactions among nectarivorous birds may result in different mating patterns to those typically observed in insect-pollinated plants. Mating system, realised pollen dispersal and spatial genetic structure were examined in the bird-pollinated Eucalyptus caesia, a species characterised by small, geographically disjunct populations. Nine microsatellite markers were used to genotype an entire adult stand and 181 seeds from 28 capsules collected from 6 trees. Mating system analysis using MLTR revealed moderate to high outcrossing (tm=0.479-0.806) and low estimates of correlated paternity (rp=0.136±s.e. 0.048). Paternity analysis revealed high outcrossing rates (mean=0.72) and high multiple paternity, with 64 different sires identified for 181 seeds. There was a significant negative relationship between the frequency of outcross mating and distance between mating pairs. Realised mating events were more frequent than expected with random mating for plants <40 m apart. The overall distribution of pollen dispersal distances was platykurtic. Despite extensive pollen dispersal within the stand, three genetic clusters were detected by STRUCTURE analysis. These genetic clusters were strongly differentiated yet geographically interspersed, hypothesised to be a consequence of rare recruitment events coupled with extreme longevity. We suggest that extensive polyandry and pollen dispersal is a consequence of pollination by highly mobile honeyeaters and may buffer E. caesia against the loss of genetic diversity predicted for small and genetically isolated populations.Heredity advance online publication, 17 August 2016; doi:10.1038/hdy.2016.61.
Worldwide, forests and woodlands have shown progressive declines in health as a result of global environmental changes in combination with local anthropogenic drivers. This study examined the incidence and progression of a canker disease of marri (Corymbia calophylla) caused by the endemic fungal pathogen Quambalaria coyrecup at three paired forest and anthropogenically disturbed sites in the southwest of Western Australia over 13 years. At the time of plot establishment in 2001, cankers were present on trees at all six sites with 22.7% of the assessed trees cankered. By 2014, cankers had led to the death of 6.7% of the trees, and an additional 10.0% of the trees developed cankers during this time. A further 2.3% of trees died due to causes other than canker, resulting in a final figure of 65.0% of trees remaining alive and free of cankers for the duration of the survey period. Canker incidence was significantly greater on trees present at anthropogenically disturbed sites (along roadsides and in paddocks) than forest trees (35.3% increasing to 50.7%, 10.0% increasing to 14.7%, respectively). Trunk diameter at breast height, tree height and crown ratings were not correlated with canker presence. This long-term study provides evidence of the increasing severity of this canker pathogen and the impact it is having on the survival of marri.
The surge in global efforts to understand the causes and consequences of drought on forest ecosystems has tended to focus on specific impacts such as mortality. We propose an eco-climatic framework that takes a broader view of the ecological relevance of water deficits, linking elements of exposure and resilience to cumulative impacts on a range of ecosystem processes. This eco-climatic framework is underpinned by two hypotheses: 1) exposure to water deficit can be represented probabilistically and used to estimate exposure thresholds across different vegetation types or ecosystems; and 2) the cumulative impact of a series of water deficit events is defined by attributes governing the resistance and recovery of the affected processes. We present case studies comprising Pinus edulis and Eucalyptus globulus, tree species with contrasting ecological strategies, which demonstrate how links between exposure and resilience can be examined within our proposed framework. These examples reveal how climatic thresholds can be defined along a continuum of vegetation functional responses to water deficit regimes. The strength of this framework lies in identifying climatic thresholds on vegetation function in the absence of more complete mechanistic understanding, thereby guiding the formulation, application and benchmarking of more detailed modelling. This article is protected by copyright. All rights reserved.
Dormant axillary buds allow plants to repair minor damage to their canopies. In woody plants, these buds subsequently develop into epicormic structures that mayallow vegetative recovery after major disturbances. They are an essential but little-studied part of the persistence niche. We wondered what bud reserves were present in the leaf axils of northern Australian myrtaceous species, what levels of protection they have, and how this relates to the ecology of these species. Axillary buds of 21 species from 10 genera of northern Australian Myrtaceae were examined anatomically. All species possessed axillary buds in all axils examined, and accessory buds were recorded in 86% of species. The species exhibited an extremely wide range of variation - from axillary buds that consisted of only an apical dome with no leaf primordia (Calytrix exstipulata) to axils with a complex array of accessory buds and meristems located beneath the axil surface (Corymbia and Eucalyptus). The axils of the Eucalyptus and Corymbia species had a greater number of and better protected axillary buds and meristems than the other species studied, including some of their closest relatives, Arillastrum, Allosyncarpia, and Stockwellia. All investigated species had an excellent meristem reserve for recovery of photosynthetic capacity after minor canopy damage and for developing epicormic structures for sprouting after more severe damage. The complex and well-protected axillary bud or meristem structures of Corymbia and Eucalyptus may be an important component of the success of these genera in Australia.
In this study, systematic variation in tree morphology across a rainfall gradient in Australia's tropical savanna biome and its implications for carbon stocks and dynamics were quantified. The aim was to support efforts to manage fire regimes to increase vegetative carbon stocks as a greenhouse gas mitigation strategy. The height of trees for a given trunk diameter declines with decreasing rainfall from 2000 to 300 mm and increasing dry season length across the Australian savanna biome. It is likely that increasing dry season length is the main driver of this decline rather declining rainfall per se. By taking account of the response of total basal area to rainfall and soil type, stand structure, and tree height and diameter relationships, the carbon stocks in live trees were estimated to decline from about 34 t ha−1 in the wetter savannas to 6 t ha−1 in the drier savannas. These values are broadly consistent with field-based estimates. Because of the declining ratio of height to trunk diameter, trees of a given diameter in drier regions will be more likely to be killed by fires of a given intensity than trees in wetter regions. Thus single fires of given intensity are likely to have a greater proportionate impact on live tree carbon stock in drier savannas, but a much greater absolute impact in wetter savannas due to the greater total carbon stock. Projected decreases in early wet season rainfall under climate change scenarios, despite projections of little change in total precipitation in northern Australia, may lead to decreased carbon stock in live trees through two mechanisms: a reduction in total basal area and decreases in tree height for given trunk diameters.
Observations and experiments on the Jignotuberous and seedling regeneration in
spotted gum - ironbark forests are recorded. The effects of annual prescribed burning,
severe wildfires, and regeneration burning on lignotubers and seedling establishment
are described. Factors having a bearing on the long-term maintenance of the lignotuber-
form are discussed. There is a striking response to complete removal of the
canopy, but development of the lignotuberous seedlings is restricted for some distance
from the edge of the surrounding canopy.
The hypothesis is advanced that there may be in these forests a complex type of
equilibrium in which the development of a given Jignotuberous or advance-growth stem
is determined by the level of stocking in a wide arc of the surrounding stand, rather
than by competitive pressure from the immediately adjacent or overtopping stems.
Predicting the consequences of climate change on forest systems is difficult because trees may display species-specific responses to exaggerated droughts that may not be reflected by the climatic envelope of their geographic range. Furthermore few studies have examined the post-drought recovery potential of drought susceptible tree species. This study develops a robust ranking of the drought susceptibility of 21 tree species based on their mortality after two droughts (1990s and 2000s) in the savanna of north-eastern Australia. Drought-induced mortality was positively related to species dominance, negatively to the ratio of post-drought seedlings to adults and had no relationship to the magnitude of extreme drought within the species current geographic ranges. These results suggest that predicting the consequences of exaggerated drought on species geographic ranges is difficult, but that dominant species like Eucalyptus with relatively slow rates of population recovery and dispersal are the most susceptible. The implications for savanna ecosystems are lower tree densities and basal area. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Eucalyptus wandoo Blakely (wandoo) has been used for timber production in Western Australia since European settlement. Today, existing wandoo woodlands are managed for a variety of purposes including conservation, landscape and timber. Regenerating wandoo after logging is a primary management objective. This study examined the effectiveness of prescribed fires set under dry soil and fuel conditions in early autumn to regenerate wandoo from seed stored in the capsules of standing trees. Regeneration was restricted to ashbeds (soil heated intensely by burning logs) on the valley floors but was occasionally also found on less intensely burnt ground on the gravelly mid-slopes. Seedlings on ashbeds exhibited superior growth and lower mortality than those growing off ashbed. Ashbed formation was promoted by burning dry logging debris under warm conditions in early autumn. However, these fires (with intensities up to 2000 kWm−1) also caused damage to the crowns and boles of living trees, such damage can be reduced by ensuring that heavy fuels, such as heaps of logs and branches, are more than 10 m from trees and that fire intensity is below 500 kWm−1. A prescription to achieve this fire intensity is presented.
Understanding how communities change with time since fire is critical for identifying appropriate fire return intervals for biodiversity conservation. In infrequently-burnt communities, vegetation structure, habitat features and fuel availability can change over time-scales much longer than can be measured using contemporary remote-sensing approaches, creating challenges for conservation and fire management. To characterize longer-term patterns of vegetation structural change, we measured vegetation cover, ground cover, tree density and stand basal area across a multi-century time-since-fire sequence derived from growth ring-size relationships in fire-sensitive Eucalyptus salubris woodlands of south-western Australia. We hypothesized that: (i) vegetation structural components reflecting fuel availability increase with time since fire; (ii) recovery of vegetation structural components with time since fire requires long time-frames; and (iii) vegetation components indicating senescence are more evident in mature than intermediate fire-age classes. All vegetation structural components showed significant differences between time-since-fire classes (termed ‘young’, ‘intermediate’ and ‘mature’), and to a lesser extent between years of sampling. The two vegetation structural components with the highest covers overall, and hence likely greatest contributors to fuel availability, were vegetation 4-10 m high and ground fuel. These two layers showed non-monotonic changes indicating a peak at intermediate times since fire (∼35-150 or 35-250 years; depending on the model used to estimate stand age), conflicting with the common assumption that fuel availability increases with time since fire. Total stand basal area increased rapidly after fire then appeared to stabilize beyond about 100 years, with competition likely mediating density-dependent thinning such that declining plant density offset increasing trunk size. There was little evidence for an increase in standing dead vegetation in mature woodlands such as would suggest significant senescence when long-unburnt. Replacement of mature woodlands with intermediate time-since-fire woodlands with greater cover and connectivity of key fuel layers potentially instigates a self-reinforcing fire regime shift favouring larger and/or more uniform fires. If such changes eventuate, substantial losses in conservation values in E. salubris woodlands are likely. Elucidating these changes in vegetation structure and implications for conservation management only became feasible due to the development of methods to estimate the time since fire of vegetation not burnt for hundreds of years.
Under future climate drought-induced tree mortality may result in the contraction of species ranges and the reorganization of community composition where abundant and peripheral species exchange their patterns of dominance. Predicting these changes will be challenging because the future suitable habitat may be a mismatch for the current bioclimatic envelope because of discrepancies between the realized and fundamental niche. Here we evaluate the extent of the discrepancy, as applied to tree species in relation to their relative field-recorded drought sensitivities and their observed range-wide environmental moisture envelopes. The hypothesis tested was that different species levels of drought-induced damage at sites where they co-occur will be positively associated with the minimum moisture availability in the most drought-prone part of each species current geographic range. We tested the hypothesis using drought damage measurements for 13 Australian Myrtaceae (including Eucalyptus) tree species at a site where all co-occur, together with 120 years of climate data across their geographical ranges. With limited statistical power the results generated only modest support for the hypothesis suggesting limited capacity to predict future distributions under climate change scenarios. In spite of the poor dispersal capacities of Eucalyptus and allied genera, but consistent with knowledge of breeding systems and genetic variability within Eucalyptus, the findings also suggest that many species have a capacity for rapid adaptive response to climate change, including the vicissitudes of the late Quaternary.
The contrasting regeneration outcomes of alpine ash (Eucalyptus delegatensis) and mountain ash (E. regnans) forests (collectively called ash) after the extensive and severe 2003, 2006/07 and 2009 bushfires in Victoria demonstrate the complexity of factors that influence the establishment of ash regeneration after bushfire. About 189 000 ha of ash forest was killed or severely damaged by the three bushfires, which burnt a land area totalling over 2.6 million ha. Silvicultural recovery work included aerial sowing of about 7100 ha of fire-killed regrowth in state forests with about 6400 kg of seed. This regrowth was less than 15–20 years of age and thus too immature to bear effective quantities of seed to achieve natural self-regeneration.This article includes a brief description of ash regeneration silviculture, a summary of relevant statistics for each of the three fires under consideration and the silvicultural recovery programs. Aspects of the recovery programs for the fires, including strategic seed-crop assessments, seedbed assessments, seed collection and management and aerial sowing operations are described, and their results are provided and discussed. The concept of ‘ecological stocking’, where regeneration levels are less than those required for commercial timber production, is also discussed.The natural seedling stocking levels resulting from the 2003 bushfires, which affected mostly alpine ash forests, were generally very satisfactory in stands of seed-bearing age. In contrast, after the bushfires of 2006/07, both natural and artificially sown eucalypt regeneration levels were often below commercial forestry standards. Natural stocking levels after the 2009 fires were again very satisfactory.
We present data on the climatic ranges of 819 species of Eucalyptus L'Herit in Australia, in terms of mean annual temperature and rainfall. 53% of species currently have ranges spanning less than 3⚬C of mean annual temperature, with 41% having a range of less than 2⚬C, and 25% with less than 1⚬C. 23% of species have ranges of mean annual rainfall that span less than 20% variation. Unless current projections greatly overestimate future climate change in Australia, within the next few decades many eucalypt species will have their entire present day populations exposed to temperatures and rainfalls under which no individuals currently exist. While we recognize that the actual climatic tolerances of many species are wider than the climatic envelope they currently occupy, the data indicate that if even a moderate proportion of present day boundaries actually reflect thermal or rainfall tolerances, substantial changes in the tree flora of Australia may be expected.
Historical records of precipitation, streamflow and drought indices all
show increased aridity since 1950 over many land areas. Analyses of
model-simulated soil moisture, drought indices and
precipitation-minus-evaporation suggest increased risk of drought in the
twenty-first century. There are, however, large differences in the
observed and model-simulated drying patterns. Reconciling these
differences is necessary before the model predictions can be trusted.
Previous studies show that changes in sea surface temperatures have
large influences on land precipitation and the inability of the coupled
models to reproduce many observed regional precipitation changes is
linked to the lack of the observed, largely natural change patterns in
sea surface temperatures in coupled model simulations. Here I show that
the models reproduce not only the influence of El Niño-Southern
Oscillation on drought over land, but also the observed global mean
aridity trend from 1923 to 2010. Regional differences in observed and
model-simulated aridity changes result mainly from natural variations in
tropical sea surface temperatures that are often not captured by the
coupled models. The unforced natural variations vary among model runs
owing to different initial conditions and thus are irreproducible. I
conclude that the observed global aridity changes up to 2010 are
consistent with model predictions, which suggest severe and widespread
droughts in the next 30-90 years over many land areas resulting from
either decreased precipitation and/or increased evaporation.
Obligate seeder trees requiring high-severity fires to regenerate may be vulnerable to population collapse if fire frequency increases abruptly. We tested this proposition using a long-lived obligate seeding forest tree, alpine ash (Eucalyptus delegatensis), in the Australian Alps. Since 2002, 85% of the Alps bioregion has been burnt by several very large fires, tracking the regional trend of more frequent extreme fire weather. High-severity fires removed 25% of aboveground tree biomass, and switched fuel arrays from low loads of herbaceous and litter fuels to high loads of flammable shrubs and juvenile trees, priming regenerating stands for subsequent fires. Single high-severity fires caused adult mortality and triggered mass regeneration, but a second fire in quick succession killed 97% of the regenerating alpine ash. Our results indicate that without interventions to reduce fire severity, interactions between flammability of regenerating stands and increased extreme fire weather will eliminate much of the remaining mature alpine ash forest. This article is protected by copyright. All rights reserved.