The impact of genetically modified crops on bird diversity

Biodiversity provides essential ecosystem services to agriculture, including pest control and pollination, yet it is declining at an alarming rate, largely due to the agricultural sector. The introduction of genetically modified (GM) crops in the United States marked a major transformation of agricultural production, as over 90% of US corn, soybean and cotton areas are now planted with GM varieties. This shift in crop cultivation has substantially altered crop management practices, most notably the types and quantities of pesticides used. Despite the magnitude of these changes, the impact on biodiversity is still poorly understood. Here we estimate the causal impact of GM crops on bird diversity in the United States and compare bird communities through time in areas with different levels of exposure to GM crops. We find that insectivorous birds benefit from GM crop adoption and that this benefit is largest in cotton. In contrast, herbivorous birds weakly decrease with GM crop adoption. Thus, while GM crop adoption has a small positive effect on overall abundance of birds, the effect is heterogeneous across species groups, with potentially important consequences for bird community composition and associated ecosystem services in agricultural landscapes.