Man-made barriers restrict movement to better territory

The physical walls that seal off national borders don’t just deter humans, they may also prevent hundreds of land-bound mammal species from migrating to escape the impacts of climate change.

New research published Monday in the journal Proceedings of the National Academy of Sciences is the first to project how man-made barriers — such as fortified fences and walls at border crossing — could restrict animals from moving to find more hospitable territory as the world both warms and becomes far drier in some places.

The researchers from Durham University in the U.K. mapped the climatic niches — areas that have appropriate temperature and precipitation conditions — of roughly 80 percent of terrestrial mammals and birds, about 12,000 species in all. They then projected where similar habitats would be in 50 years. The findings show that if humans continue to pour greenhouse gases into the atmosphere unabated, those areas will shift dramatically.

“Under a high-emissions scenario, we find that 35 percent of mammals and 29 percent of birds are projected to have over half of their 2070 climatic niches in countries in which they are not currently found,” the researchers wrote. In other words, about a third of all terrestrial and airborne species could be forced to look for new homes.

The problem, of course, is that borders between nations are already heavily fortified and growing more so all the time. The researchers say 20,000 miles of borders already are hardened enough that they have the potential to stop large numbers of animals from moving to more suitable environments when needed.

Of these barriers, the ones between the U.S. and Mexico, China and Russia, and fencing now being constructed along the India-Myanmar border stand to be the most ecologically damaging, according to the study.

The U.S.-Mexico border wall alone could obstruct the movement of 122 displaced mammal species, the authors calculated, including the puma and the Sonoran pronghorn.