Potential impact of climatic change on the distribution of forest herbs in Europe

The aim of this study is to evaluate the possible consequences of climate change on a representative sample of forest herbs in Europe. A fuzzy climatic envelope was used to predict the location of suitable climatic conditions under two climatic change scenarios. Expected consequences in terms of lost and gained range size and shift in distribution for 26 forest herbs were estimated. These results were combined in an Index of Predicted Range Change for each species. Finally, the effects of habitat fragmentation for potential dispersal routes were evaluated and options for management on a European scale are discussed. Generally, a good agreement of the estimated suitability under the present climate and the observed current distribution was observed. However, species vary a lot in the degree to which they occupy the presently climatically suitable areas in Europe. Many species are absent from large areas with suitable climate and thus could be said to have poor range‐filling capacity. A general change in location (range centroid) of the total suitable area was observed: The total suitable area will on average move strongly northwards and moderately eastwards under the relatively mild B1 scenario and more strongly so under the A2 scenario. The required average minimum migration rate per year to track the potential range shift is 2.1 km under the B1 scenario and 3.9 km under the A2 scenario. Moderate losses in the total suitable area in Europe are predicted for most species under both scenarios. However, the predicted changes are very variable, with one species (Actaea erythrocarpa) experiencing total range elimination in Europe (A2 scenario) while the total suitable area is predicted to show large increases for other species. The species that are predicted to experience the greatest proportional losses in their climatically suitable area within their presently realised range tend to have northern or eastern range centroids. The Index of Predicted Range Change roughly divides the species studied in four groups: One species face a high risk of extinction; eight species are expected to experience moderate to severe threat of extinction; 11 species are not considered at risk and, finally, six species may actually benefit from global warming. An analysis of potential migration routes shows the importance of maintaining and, if possible, improving the network of forest throughout Europe to make migration possible. It is also suggested to closely monitor the status of boreal and subalpine species that are most threatened by global warming. Finally it is recommended that special concern should be given to increased protection and restoration of forest habitats in southern montane areas for their crucial long‐term importance for the maintenance of European plant diversity.     

Quantifying components of risk for European woody species under climate change

Estimates of species extinction risk under climate change are generally based on differences in present and future climatically suitable areas. However, the locations of potentially suitable future environments (affecting establishment success), and the degree of climatic suitability in already occupied and new locations (affecting population viability) may be equally important determinants of risk. A species considered to be at low risk because its future distribution is predicted to be large, may actually be at high risk if these areas are out of reach, given the species' dispersal and migration rates or if all future suitable locations are only marginally suitable and the species is unlikely to build viable populations in competition with other species. Using bioclimatic models of 17 representative European woody species, we expand on current ways of risk assessment and suggest additional measures based on (a) the distance between presently occupied areas and areas predicted to be climatically suitable in the future and (b) the degree of change in climatic suitability in presently occupied and unoccupied locations. Species of boreal and temperate deciduous forests are predicted to face higher risk from loss of climatically suitable area than species from warmer and drier parts of Europe by 2095 using both the moderate B1 and the severe A1FI emission scenario. However, the average distance from currently occupied locations to areas predicted suitable in the future is generally shorter for boreal species than for southern species. Areas currently occupied will become more suitable for boreal and temperate species than for Mediterranean species whereas new suitable areas outside a species' current range are expected to show greater increases in suitability for Mediterranean species than for boreal and temperate species. Such additional risk measures can be easily derived and should give a more comprehensive picture of the risk species are likely to face under climate change.     

Combining climatic projections and dispersal ability: a method for estimating the responses of sandfly vector species to climate change

BACKGROUND: In the Old World, sandfly species of the genus Phlebotomus are known vectors of Leishmania, Bartonella and several viruses. Recent sandfly catches and autochthonous cases of leishmaniasis hint on spreading tendencies of the vectors towards Central Europe. However, studies addressing potential future distribution of sandflies in the light of a changing European climate are missing. METHODOLOGY: Here, we modelled bioclimatic envelopes using MaxEnt for five species with proven or assumed vector competence for Leishmania infantum, which are either predominantly located in (south-) western (Phlebotomus ariasi, P. mascittii and P. perniciosus) or south-eastern Europe (P. neglectus and P. perfiliewi). The determined bioclimatic envelopes were transferred to two climate change scenarios (A1B and B1) for Central Europe (Austria, Germany and Switzerland) using data of the regional climate model COSMO-CLM. We detected the most likely way of natural dispersal ("least-cost path") for each species and hence determined the accessibility of potential future climatically suitable habitats by integrating landscape features, projected changes in climatic suitability and wind speed. RESULTS AND RELEVANCE: Results indicate that the Central European climate will become increasingly suitable especially for those vector species with a current south-western focus of distribution. In general, the highest suitability of Central Europe is projected for all species in the second half of the 21st century, except for P. perfiliewi. Nevertheless, we show that sandflies will hardly be able to occupy their climatically suitable habitats entirely, due to their limited natural dispersal ability. A northward spread of species with south-eastern focus of distribution may be constrained but not completely avoided by the Alps. Our results can be used to install specific monitoring systems to the projected risk zones of potential sandfly establishment. This is urgently needed for adaptation and coping strategies against the emerging spread of sandfly-borne diseases.     

Warming increases the spread of an invasive thistle

Background

Global warming and shifted precipitation regimes increasingly affect species abundances and distributions worldwide. Despite a large literature on species'' physiological, phenological, growth, and reproductive responses to such climate change, dispersal is rarely examined. Our study aims to test whether the dispersal ability of a non-native, wind-dispersed plant species is affected by climate change, and to quantify the ramifications for future invasion spread rates.

Methodology/Principal Findings

We experimentally increased temperature and precipitation in a two-cohort, factorial field study (n = 80). We found an overwhelming warming effect on plant life history: warming not only improved emergence, survival, and reproduction of the thistle Carduus nutans, but also elevated plant height, which increased seed dispersal distances. Using spatial population models, we demonstrate that these empirical warming effects on demographic vital rates, and dispersal parameters, greatly exacerbate spatial spread. Predicted levels of elevated winter precipitation decreased seed production per capitulum, but this only slightly offset the warming effect on spread. Using a spread rate decomposition technique (c*-LTRE), we also found that plant height-mediated changes in dispersal contribute most to increased spread rate under climate change.

Conclusions/Significance

We found that both dispersal and spread of this wind-dispersed plant species were strongly impacted by climate change. Dispersal responses to climate change can improve, or diminish, a species'' ability to track climate change spatially, and should not be overlooked. Methods that combine both demographic and dispersal responses thus will be an invaluable complement to projections of suitable habitat under climate change.     

Where will species on the move go? Insights from climate connectivity modelling across European terrestrial habitats

Climate change can induce species range shifts. However, the intensity of climate change, the intrinsic dispersal ability of species and the anthropization of landscapes are impeding species movements in most cases. In this context, preserving and promoting climate corridors for species to migrate from their current habitats to their future climatically similar habitats is an important strategy for preventing species extinction. Climate connectivity modelling is a tool that can identify these potential movement pathways. Here, we aimed to model connectivity between climate analogues across Europe under various ecological assumptions and climate change scenarios, in order to identify areas of high potential connectivity and to quantify variation in connectivity across a range of hypotheses. We also overlapped connectivity maps with protected areas to determine whether climate connectivity was sufficiently protected. We showed that climatic connectivity did not differ much between different scenarios of climate change, but was strongly dependent on species’ dispersal assumptions. It was also relatively similar to a scenario of non-climatic connectivity. Therefore, it may be feasible to anticipate the effect of climate change on species movements regardless of the future trajectory of climate, but the implementation of protection strategies for multiple species will certainly prove complex. Overall, protected areas were located in the regions of high and stable connectivity, but some countries lack the appropriate protection schemes, especially regarding strong protections. Our results have the potential to serve in the construction of land cover change scenarios to identify the best strategies to improve climate connectivity.     

Towards European climate risk surfaces: the extent and distribution of analogous and non-analogous climates 1931–2100

Aim Climate is an important determinant of species distributions. We assess different aspects of risk arising from future climate change by quantifying changes in the spatial distribution of future climatic conditions compared with the recent past. Location Europe. Methods A 10′ × 10′ resolution gridded data set of five climate variables was used to calculate expected changes to the area, distance and direction of 1931–60 climatic conditions under the HadCM3 climate model for four future climate scenarios based on different rates of greenhouse gas emissions (SRES scenarios). Three levels of tolerance ranges determined the thresholds for which future conditions are considered analogous to 1931–60 (pre‐warming) conditions. Results For many parts of Europe, areas with pre‐warming analogous climate conditions will be smaller and further away in the future than they are now. For any location in Europe, areas with pre‐warming analogous mean annual temperature conditions will, on average, be reduced between 23.7% (B1 scenario) and 49.7% (A1FI scenario) by 2100 when assuming a medium tolerance range. The mean distance to these areas will, on average, increase between 272 km (B1) and 645 km (A1FI). These changes are more pronounced for temperature than for water availability variables and also for narrow tolerance ranges compared to wide tolerance ranges. Using a combined measure of both temperature and precipitation variables, areas with prewarming analogous conditions are predicted to be in a more northeasterly direction in the future, but there are considerable regional differences within Europe. Main conclusions The results suggest that, for some parts of Europe, the loss of area with any suitable climatic conditions represents the greatest risk to biodiversity, but in other regions the distances that species may have to move to reach suitable climatic conditions may be a greater problem. Quantifying the distance and direction in analyses of change of climatically suitable areas can add additional information for climate change risk assessments.     

A greener Greenland? Climatic potential and long-term constraints on future expansions of trees and shrubs

Warming-induced expansion of trees and shrubs into tundra vegetation will strongly impact Arctic ecosystems. Today, a small subset of the boreal woody flora found during certain Plio-Pleistocene warm periods inhabits Greenland. Whether the twenty-first century warming will induce a re-colonization of a rich woody flora depends on the roles of climate and migration limitations in shaping species ranges. Using potential treeline and climatic niche modelling, we project shifts in areas climatically suitable for tree growth and 56 Greenlandic, North American and European tree and shrub species from the Last Glacial Maximum through the present and into the future. In combination with observed tree plantings, our modelling highlights that a majority of the non-native species find climatically suitable conditions in certain parts of Greenland today, even in areas harbouring no native trees. Analyses of analogous climates indicate that these conditions are widespread outside Greenland, thus increasing the likelihood of woody invasions. Nonetheless, we find a substantial migration lag for Greenland''s current and future woody flora. In conclusion, the projected climatic scope for future expansions is strongly limited by dispersal, soil development and other disequilibrium dynamics, with plantings and unintentional seed dispersal by humans having potentially large impacts on spread rates.     

Potential distribution of Avena sterilis L. in Europe under climate change

Avena sterilis (sterile oat) is one of the most extended and harmful weeds in Mediterranean cereal crops. A process‐based niche model for this species was developed using CLIMEX. The model was validated and used to assess the potential distribution of A. sterilis in Europe under the current climate and under two climate change scenarios. Both scenarios represent contrasting temporal patterns of economic development and CO₂ emissions. The projections under current climate conditions indicated that A. sterilis does not occupy the full extent of the climatically suitable habitat available to it in Europe. Under future climate scenarios, the model projection showed a gradual advance of sterile oat towards Northeastern Europe and a contraction in Southern Europe. The infested potential area increases from the current 45.2% to 51.3% in the low‐emission CO₂ scenario and to 59.5% under the most extreme scenario. These results provide the necessary knowledge for identifying and highlighting the potential invasion risk areas and for establishing the grounds on which to base the planning and management measures required. The main actions should be focused on controlling the large‐scale seed scattering, preventing seed dispersal into potentially suitable areas.     

Research Symposium—Aberdeen

ABSTRACT

Background: Climate change may increase the risk of biological invasions. However, current knowledge of this interaction is limited.

Aims: We aimed to quantify (1) the effect of climate change on the potential distribution of invasive plant species in Spain, (2) the importance of the area of origin of such species and (3) the vulnerability of different biogeographic provinces to future changes in climatic suitability for invaders.

Methods: We applied six methods of species distribution modelling to assess the variation of climatically suitable areas for 40 alien plants. We developed a Potential Area Change Index and used it as the response variable in modelling for three future emissions scenarios and three global circulation models over three time periods. The area of origin and biogeographic province in Spain were also considered.

Results: We found a highly specific response for each plant species rather than a clear trend for the entire set of species. Predicted climate suitability increased over higher emission scenarios and longer projected time lags. Neotropical species showed the greatest potential climatic range expansion. We detected a strong interaction between the geographic origin of a species and the biogeographic province.

Conclusions: Special attention should be given to the areas where aridification of climate is projected and where introduced neotropical species are likely to expand their range. Future work should develop accurate species-specific approaches that allow the management invasive plant species.     

Modelling distribution in European stream macroinvertebrates under future climates

Climate change is predicted to have profound effects on freshwater organisms due to rising temperatures and altered precipitation regimes. Using an ensemble of bioclimatic envelope models (BEMs), we modelled the climatic suitability of 191 stream macroinvertebrate species from 12 orders across Europe under two climate change scenarios for 2080 on a spatial resolution of 5 arc minutes. Analyses included assessments of relative changes in species’ climatically suitable areas as well as their potential shifts in latitude and longitude with respect to species’ thermal preferences. Climate‐change effects were also analysed regarding species’ ecological and biological groupings, namely (1) endemicity and (2) rarity within European ecoregions, (3) life cycle, (4) stream zonation preference and (5) current preference. The BEMs projected that suitable climate conditions would persist in Europe in the year 2080 for nearly 99% of the modelled species regardless of the climate scenario. Nevertheless, a decrease in the amount of climatically suitable areas was projected for 57–59% of the species. Depending on the scenario, losses could be of 38–44% on average. The suitable areas for species were projected to shift, on average, 4.7–6.6° north and 3.9–5.4° east. Cold‐adapted species were projected to lose climatically suitable areas, while gains were expected for warm‐adapted species. When projections were analysed for different species groupings, only endemics stood out as a particular group. That is, endemics were projected to lose significantly larger amounts of suitable climatic areas than nonendemic species. Despite the uncertainties involved in modelling exercises such as this, the extent of projected distributional changes reveals further the vulnerability of freshwater organisms to climate change and implies a need to understand the consequences for ecological function and biodiversity conservation.     

Immigrants and refugees: the importance of dispersal in mediating biotic attrition under climate change

Montane tropical rainforests are critically important areas for global bird diversity, but are projected to be highly vulnerable to contemporary climate change. Upslope shifts of lowland species may partially offset declines in upland species but also result in a process of lowland biotic attrition. This latter process is contingent on the absence of species adapted to novel warm climates, and isolation from pools of potential colonizers. In the Australian Wet Tropics, species distribution modelling has forecast critical declines in suitable environmental area for upland endemic birds, raising the question of the future role of both natural and assisted dispersal in species survival, but information is lacking for important neighbouring rainforest regions. Here we use expanded geographic coverage of data to model the realized distributions of 120 bird species found in north‐eastern Australian rainforest, including species from potential source locations in the north and recipient locations in the south. We reaffirm previous conclusions as to the high vulnerability of this fauna to global warming, and extend the list of species whose suitable environmental area is projected to decrease. However, we find that expansion of suitable area for some species currently restricted to northern rainforests has the potential to offset biotic attrition in lowland forest of the Australian Wet Tropics. By examining contrasting dispersal scenarios, we show that responses to climate change in this region may critically depend on dispersal limitation, as climate change shifts the suitable environmental envelopes of many species south into currently unsuitable habitats. For lowland and northern species, future change in vegetation connectivity across contemporary habitat barriers is likely to be an important mediator of climate change impacts. In contrast, upland species are projected to become increasingly isolated and restricted. Their survival is likely to be more dependent on the viability of assisted migration, and the emergence and persistence of suitable environments at recipient locations.     

Simulating plant invasion dynamics in mountain ecosystems under global change scenarios

Across the globe, invasive alien species cause severe environmental changes, altering species composition and ecosystem functions. So far, mountain areas have mostly been spared from large‐scale invasions. However, climate change, land‐use abandonment, the development of tourism and the increasing ornamental trade will weaken the barriers to invasions in these systems. Understanding how alien species will react and how native communities will influence their success is thus of prime importance in a management perspective. Here, we used a spatially and temporally explicit simulation model to forecast invasion risks in a protected mountain area in the French Alps under future conditions. We combined scenarios of climate change, land‐use abandonment and tourism‐linked increases in propagule pressure to test if the spread of alien species in the region will increase in the future. We modelled already naturalized alien species and new ornamental plants, accounting for interactions among global change components, and also competition with the native vegetation. Our results show that propagule pressure and climate change will interact to increase overall species richness of both naturalized aliens and new ornamentals, as well as their upper elevational limits and regional range‐sizes. Under climate change, woody aliens are predicted to more than double in range‐size and herbaceous species to occupy up to 20% of the park area. In contrast, land‐use abandonment will open new invasion opportunities for woody aliens, but decrease invasion probability for naturalized and ornamental alien herbs as a consequence of colonization by native trees. This emphasizes the importance of interactions with the native vegetation either for facilitating or potentially for curbing invasions. Overall, our work highlights an additional and previously underestimated threat for the fragile mountain flora of the Alps already facing climate changes, land‐use transformations and overexploitation by tourism.     

Climate change, anthropogenic disturbance and the northward range expansion of Lactuca serriola (Asteraceae)

Aim The distribution range of Lactuca serriola, a species native to the summer‐dry mediterranean climate, has expanded northwards during the last 250 years. This paper assesses the influence of climate on the range expansion of this species and highlights the importance of anthropogenic disturbance to its spread. Location Central and Northern Europe. Methods Data on the geographic distribution of L. serriola were assembled through a literature search as well as through floristic and herbarium surveys. Maps of the spread of L. serriola in Central and Northern Europe were prepared based on herbarium data. The spread was assessed more precisely in Germany, Austria and Great Britain by pooling herbarium and literature data. We modelled the bioclimatic niche of the species using occurrence and climatic data covering the last century to generate projections of suitable habitats under the climatic conditions of five time periods. We tested whether the observed distribution of L. serriola could be explained for each time period, assuming that the climatic niche of the species was conserved across time. Results The species has spread northwards since the beginning of the 19th century. We show that climate warming in Europe increased the number of sites suitable for the species at northern latitudes. Until the late 1970s, the distribution of the species corresponded to the climatically suitable sites available. For the last two decades, however, we could not show any significant relationship between the increase in suitable sites and the distributional range change of L. serriola. However, we highlight potential areas the species could spread to in the future (Great Britain, southern Scandinavia and the Swedish coast). It is predominantly non‐climatic influences of global change that have contributed to its rapid spread. Main conclusions The observation that colonizing species are not filling their climatically suitable range might imply that, potentially, other ruderal species could expand far beyond their current range. Our work highlights the importance of historical floristic and herbarium data for understanding the expansion of a species. Such historical distributional data can provide valuable information for those planning the management of contemporary environmental problems, such as species responses to environmental change.     

Inferring the past to predict the future: climate modelling predictions and phylogeography for the freshwater gastropod Radix balthica (Pulmonata, Basommatophora)

Understanding the impact of past climatic events on species may facilitate predictions of how species will respond to future climate change. To this end, we sampled populations of the common pond snail Radix balthica over the entire species range (northwestern Europe). Using a recently developed analytical framework that employs ecological niche modelling to obtain hypotheses that are subsequently tested with statistical phylogeography, we inferred the range dynamics of R. balthica over time. A Maxent modelling for present-day conditions was performed to infer the climate envelope for the species, and the modelled niche was used to hindcast climatically suitable range at the last glacial maximum (LGM) c . 21 000 years ago. Ecological niche modelling predicted two suitable areas at the LGM within the present species range. Phylogeographic model selection on a COI mitochondrial DNA data set confirmed that R. balthica most likely spread from these two disjunct refuges after the LGM. The match observed between the potential range of the species at the LGM given its present climatic requirements and the phylogeographically inferred refugial areas was a clear argument in favour of niche conservatism in R. balthica , thus allowing to predict the future range. The subsequent projection of the potential range under a global change scenario predicts a moderate pole-ward shift of the northern range limits, but a dramatic loss of areas currently occupied in France, western Great Britain and southern Germany.     

Climate warming and the decline of amphibians and reptiles in Europe

Aim We explore the relationship between current European distributions of amphibian and reptile species and observed climate, and project species potential distributions into the future. Potential impacts of climate warming are assessed by quantifying the magnitude and direction of modelled distributional shifts for every species. In particular we ask, first, what proportion of amphibian and reptile species are projected to lose and gain suitable climate space in the future? Secondly, do species projections vary according to taxonomic, spatial or environmental properties? And thirdly, what climate factors might be driving projections of loss or gain in suitable environments for species? Location Europe. Methods Distributions of species are modelled with four species–climate envelope techniques (artificial neural networks, generalized linear models, generalized additive models, and classification tree analyses) and distributions are projected into the future using five climate‐change scenarios for 2050. Future projections are made considering two extreme assumptions: species have unlimited dispersal ability and species have no dispersal ability. A novel hybrid approach for combining ensembles of forecasts is then used to group linearly covarying projections into clusters with reduced inter‐model variability. Results We show that a great proportion of amphibian and reptile species are projected to expand distributions if dispersal is unlimited. This is because warming in the cooler northern ranges of species creates new opportunities for colonization. If species are unable to disperse, then most species are projected to lose range. Loss of suitable climate space for species is projected to occur mainly in the south‐west of Europe, including the Iberian Peninsula, whilst species in the south‐east are projected to gain suitable climate. This is because dry conditions in the south‐west are projected to increase, approaching the levels found in North Africa, where few amphibian species are able to persist. Main conclusions The impact of increasing temperatures on amphibian and reptile species may be less deleterious than previously postulated; indeed, climate cooling would be more deleterious for the persistence of amphibian and reptile species than warming. The ability of species to cope with climate warming may, however, be offset by projected decreases in the availability of water. This should be particularly true for amphibians. Limited dispersal ability may further increase the vulnerability of amphibians and reptiles to changes in climate.     

Geographical potential of Argentine ants (Linepithema humile Mayr) in the face of global climate change

Determining the spread and potential geographical distribution of invasive species is integral to making invasion biology a predictive science. We assembled a dataset of over 1000 occurrences of the Argentine ant (Linepithema humile), one of the world's worst invasive alien species. Native to central South America, Argentine ants are now found in many Mediterranean and subtropical climates around the world. We used this dataset to assess the species' potential geographical and ecological distribution, and to examine changes in its distributional potential associated with global climate change, using techniques for ecological niche modelling. Models developed were highly predictive of the species' overall range, including both the native distributional area and invaded areas worldwide. Despite its already widespread occurrence, L. humile has potential for further spread, with tropical coastal Africa and southeast Asia apparently vulnerable to invasion. Projecting ecological niche models onto four general circulation model scenarios of future (2050s) climates provided scenarios of the species' potential for distributional expansion with warming climates: generally, the species was predicted to retract its range in tropical regions, but to expand at higher latitude areas.     

MigClim: Predicting plant distribution and dispersal in a changing climate

Aim Many studies have forecasted the possible impact of climate change on plant distributions using models based on ecological niche theory, but most of them have ignored dispersal‐limitations, assuming dispersal to be either unlimited or null. Depending on the rate of climatic change, the landscape fragmentation and the dispersal capabilities of individual species, these assumptions are likely to prove inaccurate, leading to under‐ or overestimation of future species distributions and yielding large uncertainty between these two extremes. As a result, the concepts of ‘potentially suitable’ and ‘potentially colonizable’ habitat are expected to differ significantly. To quantify to what extent these two concepts can differ, we developed Mig Clim, a model simulating plant dispersal under climate change and landscape fragmentation scenarios. Mig Clim implements various parameters, such as dispersal distance, increase in reproductive potential over time, landscape fragmentation or long‐distance dispersal. Location Western Swiss Alps. Methods Using our Mig Clim model, several simulations were run for two virtual species by varying dispersal distance and other parameters. Each simulation covered the 100‐year period 2001–2100 and three different IPCC‐based temperature warming scenarios were considered. Results of dispersal‐limited projections were compared with unlimited and no‐dispersal projections. Results Our simulations indicate that: (1) using realistic parameter values, the future potential distributions generated using Mig Clim can differ significantly (up to more than 95% difference in colonized surface) from those that ignore dispersal; (2) this divergence increases under more extreme climate warming scenarios and over longer time periods; and (3) the uncertainty associated with the warming scenario can be as large as the one related to dispersal parameters. Main conclusions Accounting for dispersal, even roughly, can importantly reduce uncertainty in projections of species distribution under climate change scenarios.     

Predicting the impact of climate change on Australia's most endangered snake, Hoplocephalus bungaroides

Aim  To predict how the bioclimatic envelope of the broad-headed snake (BHS) ( Hoplocephalus bungaroides ) may be redistributed under future climate warming scenarios.
Location  South-eastern New South Wales, Australia.
Methods  We used 159 independent locations for the species and 35 climatic variables to model the bioclimatic envelope for the BHS using two modelling approaches – B ioclim and M axent . Predictions were made under current climatic conditions and we also predicted the species distribution under low and high climate change scenarios for 2030 and 2070.
Results  Broad-headed snakes currently encompass their entire bioclimatic envelope. Both modelling approaches predict that suitable climate space for BHS will be lost to varying degrees under both climate warming scenarios, and under the worst case, only 14% of known snake populations may persist.
Main conclusions  Areas of higher elevation within the current range will be most important for persistence of this species because they will remain relatively moist and cool even under climate change and will match the current climate envelope. Conservation efforts should focus on areas where suitable climate space may persist under climate warming scenarios. Long-term monitoring programs should be established both in these areas and where populations are predicted to become extirpated, so that we can accurately determine changes in the distribution of this species throughout its range.     

Change in climatically suitable breeding distributions reduces hybridization potential between Vermivora warblers

Aim

Climate change is affecting the distribution of species and subsequent biotic interactions, including hybridization potential. The imperiled Golden-winged Warbler (GWWA) competes and hybridizes with the Blue-winged Warbler (BWWA), which may threaten the persistence of GWWA due to introgression. We examined how climate change is likely to alter the breeding distributions and potential for hybridization between GWWA and BWWA.

Location

North America.

Methods

We used GWWA and BWWA occurrence data to model climatically suitable conditions under historical and future climate scenarios. Models were parameterized with 13 bioclimatic variables and 3 topographic variables. Using ensemble modeling, we estimated historical and modern distributions, as well as a projected distribution under six future climate scenarios. We quantified breeding distribution area, the position of and amount of overlap between GWWA and BWWA distributions under each climate scenario. We summarized the top explanatory variables in our model to predict environmental parameters of the distributions under future climate scenarios relative to historical climate.

Results

GWWA and BWWA distributions are projected to substantially change under future climate scenarios. GWWA are projected to undergo the greatest change; the area of climatically suitable breeding season conditions is expected to shift north to northwest; and range contraction is predicted in five out of six future climate scenarios. Climatically suitable conditions for BWWA decreased in four of the six future climate scenarios, while the distribution is projected to shift east. A reduction in overlapping distributions for GWWA and BWWA is projected under all six future climate scenarios.

Main Conclusions

Climate change is expected to substantially alter the area of climatically suitable conditions for GWWA and BWWA, with the southern portion of the current breeding ranges likely to become climatically unsuitable. However, interactions between BWWA and GWWA are expected to decline with the decrease in overlapping habitat, which may reduce the risk of genetic introgression.