To see how the animals in those areas were affected, the researchers scoured scientific literature for reports on mammals that lived there. Their list included antelopes, giraffes, elephants, lions, cheetahs, zebras, baboons, gorillas, warthogs, hyenas, rhinoceroses, hippopotamuses and gazelles.
They were able to find information on 253 populations of animals from 36 species living in 126 protected areas within 19 countries. Each of these populations had been counted multiple times in the same area.
Then they built a series of mathematical models to see which factors helped explain the changes in those animal populations. The frequency of armed conflict was only one of the factors considered; others included the intensity of those conflicts (as measured by human death toll), the population density of humans living nearby, the distance from a protected area to the nearest urban center, the size of the protected areas and the size of the animals.
The models that did the best job of predicting changes in animal populations relied on information about the frequency of armed conflicts, according to the study. These models showed that when protected areas were peaceful, animal populations were "generally stable," Daskin and Pringle wrote. But populations shrank over time when their homes were exposed to "even low levels of conflict," the researchers wrote.
Over the entire 65-year period, all it took to set animal populations on a path of decline was a single year of war in a span of two decades. When the team narrowed its focus to the more recent period from 1989 to 2010, it found animals were even more sensitive -- exposure to war in one year of a 50-year span would hinder a population's ability to maintain itself.
"Conflict frequency consistently predicted wildlife decline," the researchers wrote.
Other things did not. For instance, the size of the protected areas didn't seem to have any bearing on the populations of the animals living in them. Nor did the intensity of the conflict going on around them.
These and other findings led the researchers to hypothesize that military activity per se isn't the problem for animals; rather, it's "the effects of socioeconomic upheaval and livelihood disruption associated conflict" that are making a difference.
Further research will be needed to see whether their hypothesis is correct, the researchers wrote.
They also noted a potential silver lining: Although a small amount of war exposure had a measurable effect on wild animals, the size of that effect was "less severe" than previous research would have led them to expect.
Even in locations subjected to many years of armed conflict, examples of "extinction events" were rare. The researchers took this as a sign that "post-conflict recovery will typically be possible."
There's already some anecdotal evidence to support this optimistic view, Daskin and Pringle wrote: Efforts by government officials, scientists and conservation experts have helped restore wildlife populations in Mozambique's Gorongosa National Park as well as in Rwanda's Akagera National Park.
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