Its primary purpose was strategic deforestation, destroying the forest cover and food resources necessary for the implementation and sustainability of the North Vietnamese style of guerilla warfare.Agent Orange usage reached an apex during Operation Ranch Hand, in which the material (with its extremely toxic impurity, dioxin) was sprayed over 4.5 million acres of land in Vietnam from 1961 to 1971."[6] Independent scientific analyses of the epidemiology of Agent Orange suggest that there is little to no margin of exposure for dioxin or dioxin-like compounds on vertebrates, meaning that even passive contact or genetic lineage has devastating repercussions.[8] Dioxin levels were corroborated in subsequent studies, most notably those conducted in areas geographically near bombing sites and spray missions during the course of Operation Ranch Hand, approximately between 1962 and 1970.[9] Meta-studies have affirmed the dioxin pathway of genetic inheritance, e.g. a statistically significant correlation between paternal exposure to Agent Orange and spina bifida over three case-control studies from 1966 to 2008 (Ngo et al., 2009)."[9] Studies in the Aluoi Valley, a village near a now-defunct military base that was operating between 1963 and 1966, confirmed this process of biological magnification, as contaminated soil acted as "reservoirs" of TCDD Agent Orange toxin that would later transfer to fish and ducks and finally to humans, all via consumption.[18] Farm land that was destroyed in the process of militarization and the creation of battlefields produced an agricultural wasteland, forcing Vietnamese farmers to work with contaminated soil for more than 40 years.[21][22][23][24][25] The use of Agent Orange is considered a "notorious example" of the expropriation of human environment for warfare, forcing many rural Vietnamese to move to cities as ecological refugees to survive because their crops and livelihood had been destroyed.[32] Law reviews have even called for a revision to the litigation process in the US due to the harmful implications regarding justice, reparations, and accountability as a result of the political sway of aggregate private interests.The US-Vietnam Dialogue Group on Agent Orange/Dioxin of the Aspen Institute established a 10-year Plan of Action on June 16, 2010, to call for governmental participation in addressing herbicide effect in Vietnam.