Showing papers by "Stephen E. Williams published in 2013"

Quantifying the benefit of early climate change mitigation in avoiding biodiversity loss

Abstract: Climate change is expected to have significant influences on terrestrial biodiversity at all system levels, including species-level reductions in range size and abundance, especially amongst endemic species. However, little is known about how mitigation of greenhouse gas emissions could reduce biodiversity impacts, particularly amongst common and widespread species. Our global analysis of future climatic range change of common and widespread species shows that without mitigation, 57±6% of plants and 34±7% of animals are likely to lose ≥50% of their present climatic range by the 2080s. With mitigation, however, losses are reduced by 60% if emissions peak in 2016 or 40% if emissions peak in 2030. Thus, our analyses indicate that without mitigation, large range contractions can be expected even amongst common and widespread species, amounting to a substantial global reduction in biodiversity and ecosystem services by the end of this century. Prompt and stringent mitigation, on the other hand, could substantially reduce range losses and buy up to four decades for climate change adaptation.

Riparian Ecosystems in the 21st Century: Hotspots for Climate Change Adaptation?

Abstract: Riparian ecosystems in the 21st century are likely to play a critical role in determining the vulnerability of natural and human systems to climate change, and in influencing the capacity of these systems to adapt. Some authors have suggested that riparian ecosystems are particularly vulnerable to climate change impacts due to their high levels of exposure and sensitivity to climatic stimuli, and their history of degradation. Others have highlighted the probable resilience of riparian ecosystems to climate change as a result of their evolution under high levels of climatic and environmental variability. We synthesize current knowledge of the vulnerability of riparian ecosystems to climate change by assessing the potential exposure, sensitivity, and adaptive capacity of their key components and processes, as well as ecosystem functions, goods and services, to projected global climatic changes. We review key pathways for ecological and human adaptation for the maintenance, restoration and enhancement of riparian ecosystem functions, goods and services and present emerging principles for planned adaptation. Our synthesis suggests that, in the absence of adaptation, riparian ecosystems are likely to be highly vulnerable to climate change impacts. However, given the critical role of riparian ecosystem functions in landscapes, as well as the strong links between riparian ecosystems and human well-being, considerable means, motives and opportunities for strategically planned adaptation to climate change also exist. The need for planned adaptation of and for riparian ecosystems is likely to be strengthened as the importance of many riparian ecosystem functions, goods and services will grow under a changing climate. Consequently, riparian ecosystems are likely to become adaptation ‘hotspots’ as the century unfolds.

Increasing arboreality with altitude: a novel biogeographic dimension

Abstract: Biodiversity is spatially organized by climatic gradients across elevation and latitude. But do other gradients exist that might drive biogeographic patterns? Here, we show that rainforest's vertical strata provide climatic gradients much steeper than those offered by elevation and latitude, and biodiversity of arboreal species is organized along this gradient. In Philippine and Singaporean rainforests, we demonstrate that rainforest frogs tend to shift up in the rainforest strata as altitude increases. Moreover, a Philippine-wide dataset of frog distributions shows that frog assemblages become increasingly arboreal at higher elevations. Thus, increased arboreality with elevation at broad biogeographic scales mirrors patterns we observed at local scales. Our proposed 'arboreality hypothesis' suggests that the ability to exploit arboreal habitats confers the potential for larger geographical distributions because species can shift their location in the rainforest strata to compensate for shifts in temperature associated with elevation and latitude. This novel finding may help explain patterns of species richness and abundance wherever vegetation produces a vertical microclimatic gradient. Our results further suggest that global warming will 'flatten' the biodiversity in rainforests by pushing arboreal species towards the cooler and wetter ground. This 'flattening' could potentially have serious impacts on forest functioning and species survival.

Making decisions to conserve species under climate change

Abstract: Severe impacts on biodiversity are predicted to arise from climate change. These impacts may not be adequately addressed by conventional approaches to conservation. As a result, additional management actions are now being considered. However, there is currently limited guidance to help decision makers choose which set of actions (and in what order) is most appropriate for species that are considered to be vulnerable. Here, we provide a decision framework for the full complement of actions aimed at conserving species under climate change from ongoing conservation in existing refugia through various forms of mobility enhancement to ex situ conservation outside the natural environment. We explicitly recognize that allocation of conservation resources toward particular actions may be governed by factors such as the likelihood of success, cost and likely co-benefits to non-target species in addition to perceived vulnerability of individual species. As such, we use expert judgment of probable tradeoffs in resource allocation to inform the sequential evaluation of proposed management interventions.

Thermal Buffering of Microhabitats is a Critical Factor Mediating Warming Vulnerability of Frogs in the Philippine Biodiversity Hotspot

Abstract: Species may circumvent the impacts of climate warming if the habitats they use reduce ambient temperature. In this study, we identified which frog species from a tropical montane rain forest in the Philippines may be vulnerable to climate warming. To do so, we selected five anuran species that utilize four breeding habitats and identified the sensitivity and exposure of tadpoles and direct-developer eggs to heat by measuring their critical thermal maximums (CTmax) and the habitat-specific temperatures they experience. Our study species included two direct-developer frogs—one species that lays its eggs on exposed leaves, and another that lays its eggs in ferns—and three species that produce aquatic free-swimming tadpoles—two stream breeders, and one phytotelm (tree hole) breeder. We compared thermal tolerances derived from microclimates of breeding habitats with tolerances derived from macroclimate (i.e., non-buffered air temperature taken from the rain forest canopy). We also examined whether differences in CTmax existed across life-history stages (egg, metamorph/young-of-year, and adult) for the two direct-developer frog species. Habitats buffered ambient temperature and expanded thermal tolerances of all frog species. We found that direct-developers, however, are more vulnerable to increased temperatures than aquatic breeders—indicated by their high sensitivity to temperature, and exposure to high temperatures. Direct-developer eggs were more sensitive to warming than both metamorph and adult life-history stages. Thermally buffered microhabitats may represent the only protection against current and impending climate warming. Our data highlight the importance of considering sensitivity and exposure in unison when deciphering warming vulnerability of frogs.

Climate Change Refugia for Terrestrial Biodiversity: defining areas that promote species persistence and ecosystem resilience in the face of global climate change

Abstract: We are currently facing the likelihood of severe climate change before the close of the century. In the face of such a global driver of species loss, we urgently need to identify refugia that will shelter species from the worst impacts of climate change. This will be a critical component of successful conservation and management of our biodiversity. Despite this, little is known about how best to identify refugia in the landscape, and the practical strategies needed to identify, protect and expand refugia are just beginning to be developed. Identifying refugia that will protect most species, or large numbers of species, remains a complex and daunting endeavour due to the large variations in climatic and biotic requirements of species. A first step to identifying refugia for biodiversity across Australia is to locate the areas which show the least change into the future (i.e. the most environmentally stable), particularly along axes of temperature and precipitation. The second and crucial step is to identify the areas that will retain most of their biodiversity and provide opportunities for additional species to relocate to into the future. Using these approaches in this project, we take the first steps to identify refugial areas across the Australian continent under contemporary climate change scenarios. We find that the southern and eastern parts of the continent contain refugia that many species will retreat to over the next 75 years, but that the current reserve system may be inadequate to allow species to shift to and persist in these areas. Disturbingly, we also find that there is a large portion of the Australian vertebrate community for which adequate natural refugia do not appear to exist. Fine-scaled regional analyses will be required to clarify these broad findings, and we examine a number of case studies demonstrating how these regional analyses might best proceed. Lessons learnt across the multiple techniques employed in this study include: 1. High elevation areas are important refugia. 2. Tasmania and the east coast of mainland Australia contain most of the key areas for refugia into the future. 3. Results are dependent on which objectives, techniques, taxonomic groups and climate scenarios are used.

Climate Change Adaptation Strategies for Australian Birds

Abstract: In the first continental analysis of the effects of climate change on a faunal group, we identified that the climate space of 101 Australian terrestrial and inland water bird taxa is likely to be entirely gone by 2085, 16 marine taxa have breeding sites that are predicted to be at least 10% less productive than today, and 55 terrestrial taxa are likely to be exposed to more frequent or intense fires. Birds confined to Cape York Peninsula, the Wet Tropics, the Top End of the Northern Territory (particularly the Tiwi Islands), the arid zone, King Island and southern South Australia (particularly Kangaroo Island) are most likely to lose climate space. There was some variation in the predictions of the 18 climate models deployed, but all predicted that the rainforest avifauna of Cape York Peninsula is likely to face the strongest challenge from climate change, particularly taxa currently confined to the Iron and McIlwraith Ranges. For marine birds, those nesting on Lord Howe and Norfolk Islands, the Great Barrier Reef and the Houtman Abrolhos are likely to face the greatest declines in local marine productivity. Changes in local marine productivity may also affect the endemic terrestrial birds of these islands, for which no climate modelling was possible. A small group of beach-nesting and saltmarsh birds may be affected by sea level rise. Many taxa, and particularly seabirds, are potentially highly sensitive to climate change based on a set of ecological and morphological metrics. Small island taxa were most likely to be both exposed and sensitive to climate change, followed by marine and shoreline taxa. While threatened birds were more likely than non-threatened taxa to be exposed or sensitive to climate change, or both, a substantial proportion was neither. A key action that needs to be undertaken immediately is fine scale modelling of regions identified as having numerous highly exposed bird taxa, in order to identify climatic refugia within the landscape. Such refugia can then be secured and managed appropriately for the future. The most urgent ongoing action is monitoring, with support for the Atlas of Australian Birds seen as a particularly cost-effective investment. In the future, the most expensive actions will be management of refugia, and captive breeding should all other approaches to conservation in the wild fail. However, most of those for which captive breeding is recommended as a last resort are subspecies of species that are widespread, either in Australia or in New Guinea. For in situ management, the most important actions will be those that are already important – fire management, weed and feral animal control and, for marine taxa, controls on fishing. A small number of species-specific actions are suggested, and there appears to be no urgent requirement for corridors for the maintenance of taxa likely to be threatened with extinction – those few taxa not already living in areas where there are likely to be refugia will require assistance to colonise new climate space. The cost of management over the next 50 years for persistence in the face of climate change of the 396 bird taxa that are very highly exposed, sensitive or both is estimated at $18.8 million per year – $47,700 per year for each taxon. The biggest ongoing costs are monitoring and direct species management but refugia management and captive breeding may eventually be needed, and will be much more expensive.

Improved spatial estimates of climate predict patchier species distributions

Abstract: Aim: Correlative species distribution models (SDMs) combined with spatial layers of climate and species' localities represent a frequently utilized and rapid method for generating spatial estimates of species distributions. However, an SDM is only as accurate as the inputs upon which it is based. Current best-practice climate layers commonly utilized in SDM (e.g. ANUCLIM) are frequently inaccurate and biased spatially. Here, we statistically downscale 30 years of existing spatial weather estimates against empirical weather data and spatial layers of topography and vegetation to produce highly accurate spatial layers of weather. We proceed to demonstrate the effect of inaccurately quantified spatial data on SDM outcomes. Location: The Australian Wet Tropics. Methods: We use Boosted Regression Trees (BRTs) to generate 30 years of spatial estimates of daily maximum and minimum temperature for the study region and aggregate the resultant weather layers into 'accuCLIM' climate summaries, comparable with those generated by current best-practice climate layers. We proceed to generate for seven species of rainforest skink comparable SDMs within species; one model based on ANUCLIM climate estimates and another based on accuCLIM climate estimates. Results: Boosted Regression Trees weather layers are more accurate with respect to empirically measured temperature, particularly for maximum temperature, when compared to current best-practice weather layers. ANUCLIM climate layers are least accurate in heavily forested upland regions, frequently over-predicting empirical mean maximum temperature by as much as 7°. Distributions of the focal species as predicted by accuCLIM were more fragmented and contained less core distributional area. Conclusion: Combined these results reveal a source of bias in climate-based SDMs and indicate a solution in the form of statistical downscaling. This technique will allow researchers to produce fine-grained, ground-truthed spatial estimates of weather based on existing estimates, which can be aggregated in novel ways, and applied to correlative or process-based modelling techniques.

Current analogues of future climate indicate the likely response of a sensitive montane tropical avifauna to a warming world.

Abstract: Among birds, tropical montane species are likely to be among the most vulnerable to climate change, yet little is known about how climate drives their distributions, nor how to predict their likely responses to temperature increases. Correlative models of species' environmental niches have been widely used to predict changes in distribution, but direct tests of the relationship between key variables, such as temperature, and species' actual distributions are few. In the absence of historical data with which to compare observations and detect shifts, space-for-time substitutions, where warmer locations are used as analogues of future conditions, offer an opportunity to test for species' responses to climate. We collected density data for rainforest birds across elevational gradients in northern and southern subregions within the Australian Wet Tropics (AWT). Using environmental optima calculated from elevational density profiles, we detected a significant elevational difference between the two regions in ten of 26 species. More species showed a positive (19 spp.) than negative (7 spp.) displacement, with a median difference of ∼80.6 m across the species analysed that is concordant with that expected due to latitudinal temperature differences (∼75.5 m). Models of temperature gradients derived from broad-scale climate surfaces showed comparable performance to those based on in-situ measurements, suggesting the former is sufficient for modeling impacts. These findings not only confirm temperature as an important factor driving elevational distributions of these species, but also suggest species will shift upslope to track their preferred environmental conditions. Our approach uses optima calculated from elevational density profiles, offering a data-efficient alternative to distribution limits for gauging climate constraints, and is sensitive enough to detect distribution shifts in this avifauna in response to temperature changes of as little as 0.4 degrees. We foresee important applications in the urgent task of detecting and monitoring impacts of climate change on montane tropical biodiversity.

A significant range extension for the Australian Wet Tropics skink Eulamprus frerei (Reptilia: Squamata: Scincidae)

Abstract: The known range of Eulamprus frerei is extended approximately 110 km north-northwest of Mt Lewis (16.510°S, 145.269°E) on Mt Carbine Tableland, North Queensland. This record is form 200 m lower than the reported minimum elevation for species. Despite extensive surveys throughout Australian Wet tropics, this is the first record of E. frerei outside the Bellenden Ker Range. Additional details are given for a previously reported record from Mt Bellenden Ker.