As if biodiversity wasn’t under siege already from encroaching human populations and climate change, it is literally under attack, according to a new study showing that most of the last half-century's conflicts were in the most ecologically rich—and threatened—parts of the planet.

One hundred eighteen of 146 of the wars fought between 1950 and 2000 occurred in biodiversity hot spots, according to the study in Conservation Biology. There are 34 of those hot spots—defined as areas with at least half of all known plant species and at least 42 percent of terrestrial vertebrates—on the globe, based on criteria established in 1988 to prioritize conservation goals.

Many of the conflicts were in Africa and Southeast Asia. Wars such as the ethnic conflict that led to the Rwandan genocide, for example, were waged in the Eastern Afromontane, an intermittently mountainous region rich in flora, mammals, birds and amphibians that stretches from Zimbabwe to the Arabian Peninsula. Southeast Asian conflicts, including the Vietnam War, occurred in the Indo-Burma hot spot, which contains a wealth of turtles and birds.

Some of the link between war and biodiversity seems obvious: people settle in areas where there is an abundance of fresh water, food, and materials for shelter, and if any of those resources grow thin, war might break out. But scientists are looking at the connection through a wider lens as part of a new field of research dubbed "warfare ecology" that examines war preparations, the wars themselves and lingering postwar activities and their relationship to ecosystems.

In some cases, hot spots are the scene of war because their remoteness offers cover to rebel groups, says co-author Thor Hanson, a conservation biologist and member of the University of Idaho's human ecosystems study group. In the case of the Vietnam War, for example, destroying rainforest cover and cropland with Agent Orange was part of the U.S. strategy against the Viet Cong.

Elsewhere, the relationship is more complicated. In the case of the decade-long conflict in the Democratic Republic of Congo, neighboring countries have been drawn in partly because of the country's "lootable resources," including gold, timber, diamonds and colombo-tantalite ore (coaltan), a mineral used as a component in cell phones, Hanson says. During the Rwandan conflict, soldiers fighting in the country's Akagera National Park—which before the fighting was home to antelope, buffalo, impalas and lions—killed forest wildlife, as did poachers, according to a study in the journal Biodiversity and Conservation. And refugees stressed necessary resources such as firewood. (See our slide show on how Africa's environment has changed over the last three decades from plundering of its forests for timber.)

The new study doesn’t quantify how much habitat loss is caused by war. But global warming and its effects on climate is a "threat multiplier" for war by making the availability of natural resources such as fresh water and food unpredictable, Hanson says. Further drought in the Sahel (the region along the southern edge of the Sahara Desert) could add increased stress in Darfur, Sudan, which has been torn by genocide that some say has been driven by water shortages.

The hot spots "have seen a lot of habitat lost over the years and there's the idea that damage to ecological systems contributes to conflict because people rely on those systems, and when resources are degraded that exacerbates conflicts," Hanson says. "They’ve been historically an important part of war and are expected to increase as the population grows."

Agent Orange cropdusting in Vietnam War/U.S. Military via Wikimedia Commons