• Energy Research

AbstractMost studies of the effects of global changes on biodiversity focus on a single threat, but multiple threats lead to species extinction. We lack spatially explicit assessments of the intensity of multiple threats and their impacts on biodiversity. Here, we used a novel metric of cumulative threats and impacts to assess the consequences of multiple threats on 196 endemic species across the USA. We predict that large areas with high cumulative impact scores for amphibians, birds, mammals and reptiles will be concentrated in the eastern part of the USA by the 2050 s and 2080 s. These high cumulative impact values are due mainly to the presence of invasive species, climate change, cropland and pasture areas; additionally, a significant proportion of endemic species are vulnerable to some of these threats where they occur. This analysis provides a useful means of identifying where conservation measures and monitoring programs that should consider multiple threats should be implemented in the future.

In a recent Forum article [1] we argued that conservation on islands should better incorporate climate change in management prioritization schemes. Most species at risk of extinction are threatened by multiple factors [2] including habitat loss, biological invasions, pollution, overexploitation, and climate change. In particular, biological invasions are currently the greatest cause of insular biodiversity decline [3], but climate change and sea-level rise are likely to become more significant threats in the future [4].

AbstractPolar and alpine regions are changing rapidly with global climate change. Yet, the impacts on biodiversity, especially on the invertebrate ectotherms which are dominant in these areas, remain poorly understood. Short‐term extreme temperature events, which are growing in frequency, are expected to have profound impacts on high‐latitude ectotherms, with native species being less resilient than their alien counterparts. Here, we examined in the laboratory the effects of short periodic exposures to thermal extremes on survival responses of seven native and two non‐native invertebrates from the sub‐Antarctic Islands. We found that survival of dipterans was significantly reduced under warming exposures, on average having median lethal times (LT50) of about 30 days in control conditions, which declined to about 20 days when exposed to daily short‐term maxima of 24°C. Conversely, coleopterans were either not, or were less, affected by the climatic scenarios applied, with predicted LT50 as high as 65 days under the warmest condition (daily exposures at 28°C for 2 h). The native spider Myro kerguelensis was characterized by an intermediate sensitivity when subjected to short‐term daily heat maxima. Our results unexpectedly revealed a taxonomic influence, with physiological sensitivity to heat differing between higher level taxa, but not between native and non‐native species representing the same higher taxon. The survival of a non‐native carabid beetle under the experimentally imposed conditions was very high, but similar to that of native beetles, while native and non‐native flies also exhibited very similar sensitivity to warming. As dipterans are a major element of diversity of sub‐Antarctic, Arctic and other cold ecosystems, such observations suggest that the increased occurrence of extreme, short‐term, thermal events could lead to large‐scale restructuring of key terrestrial ecosystem components both in ecosystems protected from and those exposed to the additional impacts of biological invasions.

ABSTRACTClimate change and biological invasions are among the most important drivers of biodiversity and ecosystem change. Despite major advances in understanding their ecological impacts, these drivers are often considered individually, overlooking their possible complex interrelationship. By applying structural equation modeling to an extensive nationwide dataset of 430 fish communities across 257 French lakes, we investigated how taxonomic, size, and trophic diversities are impacted by climate warming and exotic species occurrence. Our goal was to compare their relative signature or lasting impacts after these factors had taken effect and to determine whether climate warming and biological invasions mediate the current state of community diversities. Drawing on a set of interconnected hypotheses, we suggest that biological invasions could be an important indirect effect of climate warming. This aspect must be considered to fully grasp the overall effects of climate change, beyond just its direct thermal impacts. Our results support our hypothesis that climate warming negatively impacts size and trophic diversities. However, these effects are mostly mediated by the warming‐induced increase in exotic species richness, which, in turn, promotes total species richness. These results suggest that exotic species have a substantial role in determining the impact of climate change, obscuring the diversity patterns predicted by temperature alone. We conclude that the impacts of climate change cannot be understood without considering its mediated effects via biological invasions, underscoring the need to grasp their intertwined roles in predicting and managing ecological consequences.

AbstractNutrient enrichment and climate warming threaten freshwater systems. Metabolic theory and the paradox of enrichment predict that both stressors independently can lead to simpler food‐webs having fewer nodes, shorter food‐chains and lower connectance, but cancel each other's effects when simultaneously present. Yet, these theoretical predictions remain untested in complex natural systems. We inferred the food‐web structure of 256 lakes and 373 streams from standardized fish community samplings in France. Contrary to theoretical predictions, we found that warming shortens fish food‐chain length and that this effect was magnified in enriched streams and lakes. Additionally, lakes experiencing enrichment exhibit lower connectance in their fish food‐webs. Our study suggests that warming and enrichment interact to magnify food‐web simplification in nature, raising further concerns about the fate of freshwater systems as climate change effects will dramatically increase in the coming decades.

Island conservation programs have been spectacularly successful over the past five decades, yet they generally do not account for impacts of climate change. Here, we argue that the full spectrum of climate change, especially sea-level rise and loss of suitable climatic conditions, should be rapidly integrated into island biodiversity research and management.

AbstractDespite their high vulnerability, insular ecosystems have been largely ignored in climate change assessments, and when they are investigated, studies tend to focus on exposure to threats instead of vulnerability. The present study examines climate change vulnerability of islands, focusing on endemic mammals and by 2050 (RCPs 6.0 and 8.5), using trait-based and quantitative-vulnerability frameworks that take into account exposure, sensitivity, and adaptive capacity. Our results suggest that all islands and archipelagos show a certain level of vulnerability to future climate change, that is typically more important in Pacific Ocean ones. Among the drivers of vulnerability to climate change, exposure was rarely the main one and did not explain the pattern of vulnerability. In addition, endemic mammals with long generation lengths and high dietary specializations are predicted to be the most vulnerable to climate change. Our findings highlight the importance of exploring islands vulnerability to identify the highest climate change impacts and to avoid the extinction of unique biodiversity.