adjacent sections of unsprayed forest there were, respectively, 145 and 170 species of birds and 30 and 55 species of mammals. Dioxins from Agent Orange have persisted in the Vietnamese environment since the war, settling in the soil and sediment and entering the food chain through animals and fish which feed in the contaminated areas. The movement of dioxins through the food web has resulted in bioconcentration and biomagnification. The areas most heavily contaminated with dioxins are former U.S. air bases. Sociopolitical impact American policy during the Vietnam War was to destroy crops, accepting the sociopolitical impact that that would have. The RAND Corporation's Memorandum 5446-ISA/ARPA states: "the fact that the VC [the Vietcong] obtain most of their food from the neutral rural population dictates the destruction of civilian crops ... if they are to be hampered by the crop destruction program, it will be necessary to destroy large portions of the rural economy – probably 50% or more". Crops were deliberately sprayed with Agent Orange and areas were bulldozed clear of vegetation forcing many rural civilians to cities. Legal and diplomatic proceedings International The extensive environmental damage that resulted from usage of the herbicide prompted the United Nations to pass Resolution 31/72 and ratify the Environmental Modification Convention. Many states do not regard this as a complete ban on the use of herbicides and defoliants in warfare, but it does require case-by-case consideration. Article 2(4) of Protocol III of the Convention on Certain Conventional Weapons contains the "Jungle Exception", which prohibits states from attacking forests or jungles "except if such natural elements are used to cover, conceal or camouflage combatants or military objectives or are military objectives themselves".. This exception voids any protection of any military and civilian personnel from a napalm attack or something like Agent Orange, and it has been argued that it was clearly designed to cover situations like U.S. tactics in Vietnam. Class action lawsuit Since at least 1978, several lawsuits have been filed against the companies which produced Agent Orange, among them Dow Chemical, Monsanto, and Diamond Shamrock. Attorney Hy Mayerson was an early pioneer in Agent Orange litigation, working with environmental attorney Victor Yannacone in 1980 on the first class-action suits against wartime manufacturers of Agent Orange. In meeting Dr. Ronald A. Codario, one of the first civilian doctors to see affected patients, Mayerson, so impressed by the fact a physician would show