The natural environment has been a strategic element of war since the first rock was thrown by the first cave dweller. The armies of ancient Rome and Assyria, to ensure the total capitulation of their enemies, reportedly sowed salt into the cropland of their foes, making the soil useless for farming an early use of military herbicide, and one of most devastating environmental effects of war. War is waged differently today, of course, and has widespread environmental impacts that last far longer.

Warfare today also occurs infrequently between independent nations; more often, armed conflict breaks out between rival factions within a nation. These localized civil wars, according to Bruch, are usually beyond the reach of international treaties and bodies of law. "Internal conflict is viewed as a matter of sovereignty an internal matter," he said. As a result, environmental damage, like human rights violations, occurs unchecked by outside organizations.

Though skirmishes, armed conflicts, and open warfare vary tremendously by region and by weapons used, the effects of war on the environment usually fall into the following broad categories:

Habitat Destruction: Perhaps the most famous example of habitat devastation occurred during the Vietnam War when U.S. forces sprayed herbicides like Agent Orange on the forests and mangrove swamps that provided cover to guerrilla soldiers.

Refugees: When warfare causes the mass movement of people, the resulting impacts on the environment can be catastrophic.

Invasive Species : Military ships, cargo airplanes, and trucks often carry more than soldiers and munitions; non-native plants and animals can also ride along, invading new areas and wiping out native species in the process.

Infrastructure Collapse: Among the first and most vulnerable targets of attack in a military campaign are the enemy's roads, bridges, utilities and other infrastructure.

Biological, Chemical, and Nuclear Weapons: The production, testing, transport and use of these advanced weapons are perhaps the single most destructive effects of war on the environment.

Scorched Earth Practices: The destruction of one's own homeland is a time-honored, albeit tragic, wartime custom.