Climate velocities and lagged species elevational shifts in mountain ranges

Mountain ranges support concentrations of climate-endangered endemic species, and are potential refugia for species retreating from the lowlands under anthropogenic climate change. Predicting the outcome for biodiversity requires knowledge of whether species are shifting uphill at the same rate as temperature isotherms (i.e. whether they are successfully tracking the velocity of climatic changes)1. Here, we provide a global assessment of the velocity of climate change in mountain ranges: applying thermal dynamic theory, deriving moist adiabatic lapse rates (MALR) using local surface temperature and water vapor. MALR varied substantially around the world, from 3 to 9°C cooling per km elevation increase. Consider the rate of terrestrial surface warming from 1971 to 2015, 24 regions can be identified as exhibiting high velocities where the isotherms have shifted more than one standard deviation of the global mean value (> 8.45 m yr-1). High velocities are typically found in relatively dry parts of the world, but also occur in wet regions with low lapse rates, such as in Northern Sumatra, Western Guiana Shield, Northern Andes, Costa Rica, Nepal, and Madagascar. Analysis of biodiversity data in relation to mountain-specific velocities revealed more cases of tracking between species and isotherms than previously suggested2 and more likely occurred at lower climate velocity. Nevertheless, upslope migrations of montane species have generally been lagging behind climate velocity. Such lags could continue to effect change even if the climate were to stabilize immediately. Reducing emissions would be expected to minimize lags, as well as slow the velocities of warming and required responses everywhere.