Connectivity under climate change in tropical forests

Rebecca A. Senior and David P. Edwards, Department of Animal and Plant Sciences, University of Sheffield, Sheffield, United Kingdom, Rebecca A. Senior, Princeton School of Public and International Affairs, Princeton University, Princeton, NJ, Jane K. Hill, Department of Biology, University of York, York, United Kingdom

Background/Question/Methods
To survive in a warming world the range of many species will shift polewards or upwards. Tropical rainforests harbour most of the world’s remaining terrestrial biodiversity, including thermally restricted forest specialists. Despite this, we lack a pantropical assessment of the potential for tropical species to reach climate analogues within existing forest cover – ‘climate connectivity’. Moreover, no study to date has tested how recent deforestation has impacted this connectivity. We combined global temperature and forest cover datasets to quantify climate connectivity across the tropics in the present day (year: 2012) and in the recent past (year: 2000). Climate connectivity was calculated based on the maximum temperature difference that could be achieved by traversing a gradient of hotter to cooler adjacent forest patches.
Results/Conclusions
We find that over 62% of tropical forest area (~10 million km2) is already incapable of facilitating range shifts to analogous future climates. In just 12 years, continued deforestation has caused a loss of climate connectivity for over 27% of surviving tropical forest, with accelerating declines in connectivity as forest loss increased. On average, if species’ ranges shift as far down climate gradients as permitted by existing forest connectivity, by 2070 they would still experience 0.77°C of warming under the least severe climate warming scenario and up to 2.6°C warming for the most severe scenario. Limiting further forest loss and focusing the global restoration agenda towards creating climate corridors are global priorities for improving resilience of tropical forest biotas under climate change.