 A 2005 study, designed to "simulate the impact of a direct overspray on a wetland" with four different agrochemicals (carbaryl (Sevin), malathion, 2,4-dichlorophenoxyacetic acid, and glyphosate in a Roundup formulation) by creating artificial ecosystems in tanks and then applying "each chemical at the manufacturer's maximum recommended application rates" found that "species richness was reduced by 15% with Sevin, 30% with malathion, and 22% with Roundup, whereas 2,4-D had no effect".The study has been used by environmental groups to argue that use of agrochemicals causes unintended harm to the environment and to biodiversity.Several studies documented surges in secondary pests within a few years of adoption of Bt cotton.