Unité de Recherche ‘Ecologie et Dynamique des Systèmes Anthropisés’ (EDYSAN, FRE 3498 CNRS-UPJV), Jules Verne University of Picardie, 1 rue des Louvels, F-80037 Amiens Cedex 1, France, email@example.com, @EkoLogIt
As climate change exceeds species’ intrinsic ability to tolerate it, species need to track suitable climatic conditions in the geographical space (distribution shifts) or adapt to the new climatic conditions in the environmental space (niche shifts) so as to avoid extinction. First, I will show that niche conservatism is more prevalent than niche differentiation suggesting that evolutionary adaptation through niche shifts is unlikely to happen over the short time scale of contemporary climate change and that species should theoretically shift their distribution synchronously. In this respect, species distribution models (SDMs) which are based on the niche conservatism hypothesis are perfect tools to test whether the magnitude of recent distribution changes match the expectations from bioclimatic velocities. However, I will also provide empirical evidence showing that the magnitude of recent range shifts is usually lower than the magnitude of expected range shifts predicted by bioclimatic SDMs, which suggests time lags in the biotic responses of living organisms to contemporary climate change. Several drivers could explain these lags, such as species’ intrinsic ability to tolerate changing climate, species’ longevity, habitat fragmentation, microclimatic buffering and compensation effect through non-climatic dimensions of the niche. I argue that deciphering this apparent paradox between the observed disequilibrium in species distribution changes under contemporary climate change and the fact that the climatic niche of species is static over space and time will help to tackle the challenge of the attribution of range changes to climate change, as these two are two sides of the same coin.