Estimating the Causal Effect of Glyphosate Aspersion on Coca Cultivation in Colombia

Deforestation and unsustainable practices are posing a severe threat to the invaluable natural treasure represented by the Amazon rain forest. Among other anthropogenic factors, illegal activities driven by organized crime, such as illegal logging, poaching, land grabbing, and coca cultivation significantly impact deforestation. In Colombia, aerial fumigation with glyphosate was a key policy for curbing coca cultivation from 1994 until 2015. This measure was eventually banned after years of opposition and debates over its effectiveness, coupled with concerns about its adverse impacts on local communities and the environment. Many studies, environmental groups, and individual legal complaints argue that health issues and environmental degradation are direct consequences of glyphosate use, although there is no universal agreement about the carcinogenic potential of glyphosate in humans among international institutions, and its environmental impact is also debated. Discussions about reinstating the use of glyphosate are still ongoing, driven in part by advocacy from the United States and certain political factions, despite significant opposition from environmental groups, local communities, and human rights organizations. In this context, this study aims to investigate the effectiveness of using fumigation with glyphosate to reduce the spread of coca plantations. We use a 15-year panel (2000-2015) of Colombian municipalities, including two-way fixed effects. To address endogeneity issues, we instrument aspersion with the number of days in which wind strength was below a certain threshold and aerial fumigation could take place. Estimates suggest that, contrary to its intended purpose, fumigation may actually lead to an increase in coca crop extension in most model specifications.