Ecoterrorism has been practiced by groups engaged in “anti-system” violence (i.e., violence against existing political structures). This kind of terrorism, also known as bioterrorism, includes, for example, threats to contaminate water supplies or to destroy or disable energy utilities, as well as practices such as the deployment of anthrax or other biological agents.

Another form of ecoterrorism, often described as environmental warfare, consists of the deliberate and illegal destruction, exploitation, or modification of the environment as a strategy of war or in times of armed conflict (including civil conflict within states). Modification of the environment that occurs during armed conflict and is likely to have widespread, long-lasting, or severe effects is proscribed by the Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques, adopted by the United Nations General Assembly in 1976. Nevertheless, such destruction has occurred with some regularity. In the 1960s and '70s, the U.S. military used the defoliant Agent Orange to destroy forest cover in Vietnam, and in 1991 Iraqi military forces retreating during the Persian Gulf War set fire to Kuwaiti oil wells, causing significant environmental damage. The Rome Statute of the International Criminal Court, adopted in 1998, defines such modification or destruction as a war crime.

Finally, the sometimes violent activities of some groups of environmental activists have been described as ecoterrorism. They include criminal trespass on the property of logging companies and other firms and obstruction of their operations, sometimes through the sabotage of company equipment or the environmentally harmless modification of natural resources in order to make them inaccessible or unsuitable for commercial use. Examples of this practice, known as “monkey-wrenching,” are the plugging of factory-waste outlets and driving spikes into trees so that they cannot be logged and milled. Other activities described as ecoterrorist include protest actions by animal-liberation groups, which have included the destruction of property in stores that sell products made of fur and the bombing of laboratories that perform experiments on animals.