Most conflicts fought in the second half of the last century were waged in biologically diverse, fragile places, with many negative consequences and a few surprising positive ones, a study said Friday.

A team of international conservation scientists found that 81 percent of conflicts fought between 1950 and 2000 in which at least 1,000 people died played out in "biodiversity hotspots" from the Himalayas in Asia to the coastal forests of east Africa.

The hotspots contain the entire populations of more than half of all plant species and at least 42 percent of all vertebrates, and are highly threatened, said the study, which was published in Conservation Biology magazine.

Of the 34 such hotspots around the globe, only 11 escaped armed conflict during the 50-year period, the authors said.

Conflicts often play out in the hotspots because fighters take advantage of the cover provided by deep forests and high mountains.

And the use of chemical, biological and nuclear weapons has increased conflict's impact on the world's fragile zones.

During the Vietnam War, for example, the United States used herbicides to exfoliate 14 percent of the southeast Asian country's forests and more than half of its coastal mangroves in a bid to deprive the enemy of shelter and sustenance, according to the study.

The impact on the key areas extends "far beyond the actual fighting," said Thor Hanson of the University of Idaho, the lead author of the study.

"War preparations and lingering post-conflict activities also have important implications for biodiversity hotspots and the people who live there," he said.

The proliferation of small arms -- the weapon of choice in most conflicts -- leads to "increased hunting for bushmeat, wildlife products and sport, often by the soldiers themselves," the study says.

In Democratic Republic of Congo, which has been wracked by conflict on and off since 1960, hippopotamus herds in Virunga National Park have been nearly wiped out by poachers, and the huge central African country's rich mineral resources have been plundered by fighters to fund the conflicts.

The humanitarian crises that inevitably accompany conflicts also impact the environment.

"During the civil war in Rwanda in the mid-1990s, over two million refugees flooded camps in neighboring countries, and the demand for fuelwood led to the deforestation of more than 300 square kilometers (116 square miles) -- or 74,000 acres (30,000 hectares) -- of land in Virunga National Park," the study says.

"Delays in repatriation and the persistence of unexploded ordnance can last for decades, perpetuating the environmental impacts of the conflict," it says.

But amid the destruction of war, the study highlights a silver lining for the environment: altered human activity in conflict areas "sometimes creates tangible conservation opportunities," it says.

The demilitarized zone separating North and South Korea is a good example of how conflict can be a friend to the environment.

The four-kilometer (2.4-mile) wide stretch of no man's land between the two neighbors has been uninhabited for decades and become a "de facto nature reserve harboring numerous threatened species," the study says.

But its authors stress that although there are a few conservation opportunities associated with conflict, "this does not mean warfare is good."