Long-term impacts of Bt cotton in India.

Most scholarship on the closely-watched case of genetically modified Bacillus thuringiensis (Bt) cotton in India has focused on short-term impacts and has also ignored other major changes in India's cotton agriculture. This Perspective combines several data sources over a 20-year span to provide long-term comparisons of Bt adoption with yields and other inputs at both countrywide and state-specific scales. Bt cotton adoption is shown to be a poor indicator of yield trends but a strong indicator of initial reductions in pesticide use. Yield increases correspond to changes in fertilizer and other inputs. Bt cotton has continued to control one major cotton pest, but with Bt resistance in another pest and surging populations of non-target pests, farmers now spend more on pesticides today than before the introduction of Bt. Indications are that the situation will continue to deteriorate.