To the list of ways that humans are making it hard for zebras, giraffes and other large mammals to survive in the wild, you can now add war.
Researchers have new evidence that animals are exquisitely vulnerable to the effects of warfare. They analyzed 65 years of armed conflicts in Africa and found that exposure to just one year of war within a 20-year period was enough to destabilize populations in the wild.
"The mere occurrence of conflict, irrespective of its human death toll, was sufficient to diminish wildlife populations," according to a study published Wednesday in the journal Nature. "Even low-grade, infrequent conflict is sufficient to drop population trajectories below replacement."
Considering that war is bad for people, it may seem obvious that it's bad for animals. But previous case studies have found it can have mixed effects.
In some cases, animals get caught in the crossfire of cannons, large guns and other artillery. Hungry soldiers go hunting for bushmeat. Poachers seeking to finance their military excursions may target elephants, rhinoceroses or other desirable species.
But in other cases, combat can scare people away from wildlife areas, relaxing the pressure on the animals that live there. It may even force businesses to abandon mining and drilling operations, giving animals a further respite.
Joshua Daskin and Robert M. Pringle of Princeton University's Department of Ecology and Evolutionary Biology wanted to see if they could find an overarching effect of warfare, with a focus on Africa.
They began by looking at all protected wildlife areas in Africa that were at least 5 square kilometers (about 2 square miles) in size. According to the World Database on Protected Areas maintained by the International Union for Conservation of Nature and the United Nations Environment Programme, there were 3,585 such areas, spread across 51 countries.
Next, Daskin and Pringle examined the dates and locations of armed conflicts between 1946 and 2010 to see when and where they overlapped with the protected areas. To qualify as an "armed conflict," an event had to involve at least one human death and be related to an "organized conflict" that involved at least 25 deaths in the same year.
Overall, they found that armed conflicts touched 71 percent of Africa's protected areas at least once during the study period. In addition, 25 percent of them experienced nine years of conflict or more.