Habitat degradation compounds climate change threat to tropical forest butterfly communities
Species globally are threatened by multiple environmental changes, often together, including habitat loss, fragmentation and climate change. However, how these changes might act in concert are poorly understood, especially in the tropics where the vast majority of biodiversity resides. Here, using a unique dataset covering 10 years of butterfly surveys at Tam Dao National Park in northern Vietnam, we examine the impacts of habitat degradation and climate change on tropical forest butterfly communities. Butterflies were surveyed across six transects (four forest transects and two open/ pasture land transects) from June to November from 2003-2013. We also examined the relationships between recorded temperatures of transects, regional weather patterns and climate change projection data to illustrate the consequences of degradation and global warming for tropical butterflies.
We found that habitat degradation in the form of road construction in the park in 2005 caused highly significant effects on the communities of forest butterflies. We also found that 1.) degradation had thermal consequences (forest sites increased in temperature after road construction), 2.) communities had greater proportions of cosmopolitan species (widely distributed) after disturbance and as a consequence of warmer temperatures, and 3.) communities had a lower proportion of forest-associated species after disturbance in addition to being less common under warmer conditions. Using these relationships we modeled the impacts of climate change on the butterfly communities of Tam Dao and found that the projected impact of warming was comparable to degradation in community change. Additionally, disturbed forests were projected to change even more to the extent that their community characteristics were similar to open habitats after climate change. The tropics are being heavily deforested world-wide but also suffer from heavy impacts of degradation and fragmentation, especially road construction. The results of this study suggest that such degradation, in addition to itself having significant ecological impacts, could compound the potential impacts of climate change for tropical biodiversity.