Amazon’s vulnerability to climate change heightened by deforestation and man-made dispersal barriers

Background/Question/Methods

Species are predicted to respond to climate change through shifts in their geographic distributions.  Species migrations have been observed in many taxonomic groups worldwide.  However, it remains uncertain if species will be able to keep pace with future climate change especially given the rate at which temperatures are rising as well as the potential influence of changes in other climatic factors (e.g. precipitation). In addition, large-scale disturbances such as deforestation and human land-use may alter patterns and required rates of species migrations.  The challenges of keeping pace with climate change through distributional shifts will be especially daunting in tropical lowland rainforests due to their high velocities of climate change and rates of deforestation, as well as lowland tropical species generally having narrow climatic tolerances. We calculated the distances between current and future (2050) climate analogs under various climate and land-use scenarios in order to create spatially-explicit maps of required migration distances and rates in the Amazon rainforest.  

Results/Conclusions

Under even the most sanguine of climate change models included (IPSL_CM4), we find that the median distance between areas in the Amazon rainforest and their closest climate analog as predicted for 2050 based on just temperature changes alone is 281km. If we include changes in precipitation, minimum required migration distances increase by an average of >70km. Since deforestation is generally concentrated in the hottest and driest portions of the Amazon, habitat loss will have little direct impact on the required migration distances (i.e., by eliminating possible future analogs). However, we predict that if deforested areas act as a barrier to species movements, 18 or 46% of the Amazon rainforest will have no reachable future climate analog under projections of reduced or business-as-usual deforestation, respectively. In addition, for those areas that will have reachable climate analogs, avoiding deforested areas increases required migration distances by a mean of 12 or 23%. These results highlight the importance of including multiple climatic factors and human land-use in predicting the effects of climate change, as well as the daunting challenges that many Amazonian species will face in the near future.