"Plant-based drugs are often grown in ecologically valuable forest areas, with immediate and devastating consequences for the environment: deforestation, degradation of the soil, and pollution. Many traditional economic activities—such as agriculture, mining, and cattle ranching—have a negative impact on natural ecosystems, in part because they tend to replace native forests with croplands. The data provided below are, consequently, valid for both licit and illicit activities. While it is not possible to determine the relative importance of each, it is likely that because of their limited scope the harm done by illicit crops is probably less than that wrought by legal activities. However, it is also possible to assert that the environmental impact is likely accelerated with illicit crops. Because they are usually grown in isolated areas far from urban centers, where there are often no roads and the state has difficulty maintaining a presence, these crops tend to expand the agricultural frontier. Moreover, the pace and methods used to produce illicit crops, which do not include measures to promote sustainability of the land, exacerbate the environmental impact.
"Beyond the effects that can be attributed directly to drug production, the process of drug control itself can complicate the problem. Some studies have maintained that aerial spraying of the herbicide glyphosate causes a negative impact on the environment and human health, which has been a particular cause for concern in regions of Colombia where this method is used to control illicit crops."
Organization of American States, General Secretariat, "The Drug Problem in the Americas," 2013, p. 33.