Abstract
AbstractAimThe Madrean Sky Island Archipelago is a North American biodiversity hotspot composed of ~60 isolated mountains that span the Cordilleran Gap between the Rocky Mountains and the Sierra Madre Occidental. Characterized by discrete patches of high‐elevation montane habitat, these “sky islands” serve as stepping stones across a “sea” of desert scrub/grassland. Over this coming century, the region is expected to shift towards a warmer and drier climate. We used species distribution modelling to predict how the spatial distribution of montane habitat will be affected by climate change.LocationMadrean Sky Island Archipelago, south‐west United States and north‐west Mexico (latitude, 29–34°N; longitude, 107–112°W).MethodsTo approximate the current distribution of montane habitat, we built species distribution models for five high‐elevation species (Ceanothus fendleri, Pinus strobiformis, Quercus gambelii, Sciurus aberti, and Synuchus dubius). The resulting models were projected under multiple climate change scenarios—four greenhouse gas concentration trajectories (RCP 2.6, 4.5, 6.0, and 8.5) for each of three climate models (CCSM4, MPI‐ESM‐LR, and NorESM1‐M)—to generate predicted distributions for the years 2050 and 2070. We performed chi‐squared tests to detect any future changes to total montane habitat area, and Conover–Iman tests to evaluate isolation among the discrete montane habitat patches.ResultsWhile the climate models differ with respect to their predictions as to how severe the effects of future climate change will be, they all agree that by as early as year 2050, there will be significant montane habitat loss and increased montane habitat patch isolation across the Madrean Archipelago region under a worst‐case climate change scenario (RCP 8.5).Main conclusionsOur results suggest that under 21st‐century climate change, the Madrean Sky Islands will become increasingly isolated due to montane habitat loss. This may affect their ability to serve as stepping stones and have negative implications for the region's biodiversity.
Highlights
Human influences on Earth's climate system are unequivocal
For each climate model under a worst‐case future climate change scenario (RCP 8.5), (a) the proportion of the Madrean Archipelago consisting of the mon‐ tane biome decreased significantly and (b) discrete patches of mon‐ tane habitat became significantly more isolated from one another
CCSM4, MPI‐Max Planck Institute Earth System Model (ESM‐LR), and NorESM1‐M contributed to CMIP5 by predicting how Earth's climate will be impacted by a range of vari‐ ables related to 21st‐century population growth, technological devel‐ opment, energy and land use, socio‐economic change, greenhouse gas emissions, and societal responses to climate change
Summary
Human influences on Earth's climate system are unequivocal. Mean annual global surface temperatures increased ~0.85°C from 1880 to 2012 and are expected to rise by an additional 1–4°C by 2100; greater contrasts in annual mean precipitation between dry and wet regions, as well as larger contrasts between dry and wet seasons, are anticipated by the end of this century (IPCC, 2013). There have been widespread local extinctions in hundreds of species across diverse climatic regions, habitats and taxonomic groups, at the warm edge (i.e., lower latitudes and lower elevations) of their ranges (Wiens, 2016). This trend will inevitably continue as projected rates of future climate change are expected to outpace species’ ability to adapt (Jezkova & Wiens, 2016). For each climate model under a worst‐case future climate change scenario (RCP 8.5), (a) the proportion of the Madrean Archipelago consisting of the mon‐ tane biome decreased significantly and (b) discrete patches of mon‐ tane habitat became significantly more isolated from one another
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