The cultivation of some of these crops in mountainous, watershed areas has adverse effects for the environment, notably the alteration of water cycles and erosion. In Peru, the cultivation of coca plants (containing the basic ingredient for cocaine) was so widespread in the Andean foothills during the 1980s and 1990s that Peruvian river flood cycles were altered in some areas, making the high-water season unpredictable. The most serious environmental concern (other than deforestation) stemming from the cultivation of coca is the dumping of chemicals (including kerosene, sulfuric acid, acetone, and carbide) used to process coca leaves. However, stopping coca cultivation is nearly impossible due to simple economics: no crop outperforms coca.