The effects of climate change on a mega‐diverse country: predicted shifts in mammalian species richness and turnover in continental Ecuador

Ecuador has some of the greatest biodiversity in the world, sheltering global biodiversity hotspots in lowland and mountain regions. Climate change will likely have a major effect on these regions, but the consequences for faunal diversity and conservation remain unclear. To address this issue, we used an ensemble of eight species distribution models to predict future shifts and identify areas of high changes in species richness and species turnover for 201 mammals. We projected the distributions using two different climate change scenarios at the 2050 horizon and contrasted two extreme dispersal scenarios (no dispersal vs. full dispersal). Our results showed extended distributional shifts all over the country. For most groups, our results predicted that the current diversity of mammals in Ecuador would decrease significantly under all climate change scenarios and dispersal assumptions. The Northern Andes and the Amazonian region would remain diversity hotspots but with a significant decrease in the number of species. All predictions, including the most conservative scenarios in terms of dispersal and climate change, predicted major changes in the distribution of mammalian species diversity in Ecuador. Primates might be the most severely affected because they would have fewer suitable areas, compared with other mammals. Our work emphasizes the need for sound conservation strategies in Ecuador to mitigate the effects of climate change     

Functional Resilience against Climate-Driven Extinctions – Comparing the Functional Diversity of European and North American Tree Floras

Future global change scenarios predict a dramatic loss of biodiversity for many regions in the world, potentially reducing the resistance and resilience of ecosystem functions. Once before, during Plio-Pleistocene glaciations, harsher climatic conditions in Europe as compared to North America led to a more depauperate tree flora. Here we hypothesize that this climate driven species loss has also reduced functional diversity in Europe as compared to North America. We used variation in 26 traits for 154 North American and 66 European tree species and grid-based co-occurrences derived from distribution maps to compare functional diversity patterns of the two continents. First, we identified similar regions with respect to contemporary climate in the temperate zone of North America and Europe. Second, we compared the functional diversity of both continents and for the climatically similar sub-regions using the functional dispersion-index (FDis) and the functional richness index (FRic). Third, we accounted in these comparisons for grid-scale differences in species richness, and, fourth, investigated the associated trait spaces using dimensionality reduction. For gymnosperms we find similar functional diversity on both continents, whereas for angiosperms functional diversity is significantly greater in Europe than in North America. These results are consistent across different scales, for climatically similar regions and considering species richness patterns. We decomposed these differences in trait space occupation into differences in functional diversity vs. differences in functional identity. We show that climate-driven species loss on a continental scale might be decoupled from or at least not linearly related to changes in functional diversity. This might be important when analyzing the effects of climate-driven biodiversity change on ecosystem functioning.     

Endemic species and ecosystem sensitivity to climate change in Namibia

We present a first assessment of the potential impacts of anthropogenic climate change on the endemic flora of Namibia, and on its vegetation structure and function, for a projected climate in ～2050 and ～2080. We used both niche‐based models (NBM) to evaluate the sensitivity of 159 endemic species to climate change (of an original 1020 plant species modeled) and a dynamic global vegetation model (DGVM) to assess the impacts of climate change on vegetation structure and ecosystem functioning. Endemic species modeled by NBM are moderately sensitive to projected climate change. Fewer than 5% are predicted to experience complete range loss by 2080, although more than 47% of the species are expected to be vulnerable (range reduction >30%) by 2080 if they are assumed unable to migrate. Disaggregation of results by life‐form showed distinct patterns. Endemic species of perennial herb, geophyte and tree life‐formsare predicted to be negatively impacted in Namibia, whereas annual herb and succulent endemic species remain relatively stable by 2050 and 2080. Endemic annual herb species are even predicted to extend their range north‐eastward into the tree and shrub savanna with migration, and tolerance of novel substrates. The current protected area network is predicted to meet its mandate by protecting most of the current endemicity in Namibia into the future. Vegetation simulated by DGVM is projected to experience a reduction in cover, net primary productivity and leaf area index throughout much of the country by 2050, with important implications for the faunal component of Namibia's ecosystems, and the agricultural sector. The plant functional type (PFT) composition of the major biomes may be substantially affected by climate change and rising atmospheric CO₂– currently widespread deciduous broad leaved trees and C₄ PFTs decline, with the C₄ PFT particularly negatively affected by rising atmospheric CO₂ impacts by ～2080 and deciduous broad leaved trees more likely directly impacted by drying and warming. The C₃ PFT may increase in prominence in the northwestern quadrant of the country by ～2080 as CO₂ concentrations increase. These results suggest that substantial changes in species diversity, vegetation structure and ecosystem functioning can be expected in Namibia with anticipated climate change, although endemic plant richness may persist in the topographically diverse central escarpment region.     

Projected changes in distributions of Australian tropical savanna birds under climate change using three dispersal scenarios

Identifying the species most vulnerable to extinction as a result of climate change is a necessary first step in mitigating biodiversity decline. Species distribution modeling (SDM) is a commonly used tool to assess potential climate change impacts on distributions of species. We use SDMs to predict geographic ranges for 243 birds of Australian tropical savannas, and to project changes in species richness and ranges under a future climate scenario between 1990 and 2080. Realistic predictions require recognition of the variability in species capacity to track climatically suitable environments. Here we assess the effect of dispersal on model results by using three approaches: full dispersal, no dispersal and a partial-dispersal scenario permitting species to track climate change at a rate of 30 km per decade. As expected, the projected distributions and richness patterns are highly sensitive to the dispersal scenario. Projected future range sizes decreased for 66% of species if full dispersal was assumed, but for 89% of species when no dispersal was assumed. However, realistic future predictions should not assume a single dispersal scenario for all species and as such, we assigned each species to the most appropriate dispersal category based on individual mobility and habitat specificity; this permitted the best estimates of where species will be in the future. Under this "realistic" dispersal scenario, projected ranges sizes decreased for 67% of species but showed that migratory and tropical-endemic birds are predicted to benefit from climate change with increasing distributional area. Richness hotspots of tropical savanna birds are expected to move, increasing in southern savannas and southward along the east coast of Australia, but decreasing in the arid zone. Understanding the complexity of effects of climate change on species' range sizes by incorporating dispersal capacities is a crucial step toward developing adaptation policies for the conservation of vulnerable species.     

Geographical patterns of community‐based tree species richness in Chinese mountain forests: the effects of contemporary climate and regional history

The relationship between climate/productivity and historical/regional contingency and their relative influence on geographical patterns of species richness (GPSR) are still unresolved. Based on field data from 1494 plots from forests on 63 mountains across China, we document the GPSR for forest communities. Regression tree and generalized linear models were used to explore the discreteness and gradient of the distribution of tree species richness (α‐diversity), and to estimate the correlations of climate, historical floristic region, and local habitat with species richness. The collinearity between climatic variables and region were further disentangled; and the spatial autocorrelation in the patterns of α‐diversity and the residuals of alternative predictive models were compared. Overall, 75% of variation in plot‐based α‐diversity of trees was accounted for by all variables included, and about 66.5%, 64.5% and 27.9% by climate, region, and local habitat respectively. Importantly, the explanatory power of these variables differed in particular for coniferous, deciduous broadleaved and evergreen broadleaved species. Ambient temperature was more important for α‐diversity of trees than were the other climatic variables across China. Spatial autocorrelation in the pattern of α‐diversity could be accounted for mainly by spatial variation climate. The concordance between tree α‐diversity, historical flora, contemporary climate, and Quaternary climate change mode suggests the climate/productivity and historical/regional contingency both contribute to the GPSR in a complimentary manner. Taken together, our results provide unique evidence to link of the effects of contemporary climate and historical climate change on species richness across scales.     

中国中亚热带东部常绿阔叶林主要类型的群落多样性特征

 本文通过10个地区61个样地资料分析,研究了中亚热带东部常绿阔叶林群落多样性特征及其随纬度、海拔梯度的变化。结果表明,中亚热带东部常绿阔叶林群落丰富度为49±17种(样地面积400m2),各层次的多样性表现为灌木层(包括幼树与幼苗)>乔木层>草本层。常绿阔叶林各类型间的差异远比落叶阔叶林与多样性较低的常绿阔叶林之间的差异大。各层次中变化幅度从大到小的顺序为：草本层>乔木层>灌木层。在所研究地区常绿阔叶林的群落多样性没有表现出明显的随纬度梯度和海拔梯度的变化规律。     

The coastal-disjunct mesic flora in the inland Pacific Northwest of USA and Canada: refugia, dispersal and disequilibrium

Aim Understanding the history of the mesic‐adapted plant species of eastern British Columbia and northern Idaho, disjunct from their main coastal distribution, may suggest how biotas reorganize in the face of climate change and dispersal barriers. For different species, current evidence supports establishment of the disjunction via an inland glacial refugium, via recent dispersal from the coast, or via a combination of both. In this study, the modern distributions of the coastal‐disjunct vascular plants are analysed with respect to modern climate to examine how refugia and/or dispersal limitation control regional patterns in species richness. Location North‐west North America. Methods The distributions of nine tree and 58 understorey species with a coastal‐disjunct pattern were compiled on a 50‐km grid. The relationship between species richness and an estimate of available moisture was calculated separately for formerly glaciated and unglaciated portions of the coastal and inland regions. Growth habit and dispersal mode were assessed as possible explanatory variables for species distributions. Results Species richness shows a strong relationship to climate in coastal‐unglaciated areas but no relationship to climate in inland‐glaciated areas. In inland‐glaciated areas, richness is c. 70% lower than that expected from climate. Species with animal‐dispersed seeds occupy a larger portion of coastal and inland regions than species with less dispersal potential. Main conclusions Modern patterns of diversity are consistent with both refugia and dispersal processes in establishing the coastal‐disjunct pattern. The inland glacial refugium is marked by locally high diversity and several co‐distributed endemics. In the inland‐glaciated area, dispersal limitation has constrained diversity despite the nearby refugia. Onset of mesic climate within only the last 3000 years and the low dispersal capacity of many species in the refugium may explain this pattern. This study suggests that vascular plant species will face significant challenges responding to climate change on fragmented landscapes.     

Climate change threats to the global functional diversity of freshwater fish

Climate change impacts on freshwater ecosystems and freshwater biodiversity show strong spatial variability, highlighting the importance of a global perspective. While previous studies on biodiversity mostly focused on species richness, functional diversity, which is a better predictor of ecosystem functioning, has received much less attention. This study aims to comprehensively assess climate change threats to the functional diversity of freshwater fish across the world, considering three complementary metrics—functional richness, evenness and divergence. We built on existing spatially explicit projections of geographical ranges for 11,425 riverine fish species as affected by changes in streamflow and water temperature extremes at four warming levels (1.5°C, 2.0°C, 3.2°C and 4.5°C). To estimate functional diversity, we considered the following four continuous, morphological and physiological traits: relative head length, relative body depth, trophic level and relative growth rate. Together, these traits cover five ecological functions. We treated missing trait values in two different ways: we either removed species with missing trait values or imputed them. Depending on the warming level, 6%–25% of the locations globally face a complete loss of functional diversity when assuming no dispersal (6%–17% when assuming maximal dispersal), with hotspots in the Amazon and Paraná River basins. The three facets of functional diversity do not always follow the same pattern. Sometimes, functional richness is not yet affected despite species loss, while functional evenness and divergence are already reducing. Other times, functional richness reduces, while functional evenness and/or divergence increase instead. The contrasting patterns of the three facets of functional diversity show their complementarity among each other and their added value compared to species richness. With increasing climate change, impacts on freshwater communities accelerate, making early mitigation critically important.     

Fast attrition of springtail communities by experimental drought and richness–decomposition relationships across Europe

Soil fauna play a fundamental role on key ecosystem functions like organic matter decomposition, although how local assemblages are responding to climate change and whether these changes may have consequences to ecosystem functioning is less clear. Previous studies have revealed that a continued environmental stress may result in poorer communities by filtering out the most sensitive species. However, these experiments have rarely been applied to climate change factors combining multiyear and multisite standardized field treatments across climatically contrasting regions, which has limited drawing general conclusions. Moreover, other facets of biodiversity, such as functional and phylogenetic diversity, potentially more closely linked to ecosystem functioning, have been largely neglected. Here, we report that the abundance, species richness, phylogenetic diversity, and functional richness of springtails (Subclass Collembola), a major group of fungivores and detritivores, decreased within 4 years of experimental drought across six European shrublands. The loss of phylogenetic and functional richness was higher than expected by the loss of species richness, leading to communities of phylogenetically similar species sharing evolutionary conserved traits. Additionally, despite the great climatic differences among study sites, we found that taxonomic, phylogenetic, and functional richness of springtail communities alone were able to explain up to 30% of the variation in annual decomposition rates. Altogether, our results suggest that the forecasted reductions in precipitation associated with climate change may erode springtail communities and likely other drought‐sensitive soil invertebrates, thereby retarding litter decomposition and nutrient cycling in ecosystems.     

Intertwined effects of defaunation,increased tree mortality and density compensation on seed dispersal

Contemporary defaunation has profound ecological consequences ranging from local or even global co-extinctions of interacting species to the loss of ecosystem functions and services critical for humanity. Other components of global change (climate change, introduced pests, land use changes) are also harming ecosystem functioning by augmenting tree mortality worldwide. Defaunation and increased tree mortality often coincide in many human-altered ecosystems but whether they interact, leading to non-additive effects on ecosystem functioning, remains largely unknown. However, under some ecological circumstances, the decline or extirpation of one species due to defaunation can be neutralized by increases in the abundance of some functionally similar species (i.e. ‘density compensation’). We combined long-term field data with individual-based modelling to investigate the potential interactive effects of seed disperser loss, increased tree mortality and density compensation on seed dispersal in a heterogeneous landscape. Our simulation experiments showed that both stressors markedly limit not only the quantity of seed dispersal but also its quality since the impact on seed dispersal strongly varied among habitat types that differ strikingly in suitability for tree establishment. Density compensation had a marked positive effect on seed dispersal which, however, was largely limited under increased tree mortality. The combined negative effects of defaunation and increased tree mortality on seed dispersal were lower than the expected additive effect. This highlights the need to account for the joint operation of multiple stressors to accurately predict the impacts of global change on the link between biodiversity and ecosystem functioning.