Bt Cotton: potential effect on biodiversity.


Cotton plants have been genetically modified to include an insecticidal protein (Cry1Ac) derived from the bacterium Bacillus thuringiensis (Bt). The use of genetically modified (GM) crops, including Bt cotton, has rapidly increased globally, with up to 30 countries adopting them, and almost 18 million farmers cultivating these crops on more than 2 billion hectares of land. In areas where Bt cotton is grown, there has been a significant reduction in insecticide applications, such as up to 14 applications in China, 5-6 in Australia, 7 in South Africa, and 2.5 in India. The introduction of Bt cotton in Southeast Asia has resulted in a 72% decrease in insecticide applications, an 11.4% increase in yield, and an estimated profit of US $126.02 per hectare. However, there are potential non-target effects.

  • Effect on non-target organisms. Cotton crops are home to a diverse range of insect predators and parasitoids that play a crucial role in controlling pest populations. While many studies suggest that Bt cotton has little to no effect on beneficial insects, concerns about long-term effects remain. For example, the use of Bt cotton and its Bt toxin may also impact pollinator species such as honey bees, which are vital for the pollination and pollen dispersal of cotton. Other species such as Meloidae, Nitidulidae, Hymenoptera, and Hemiptera have also been identified as potential pollinators for cotton. While no negative effects have been observed, the long-term impact of this genetic modification remains unknown and poses a potential risk. 
  • Ecosystem imbalance. The reduction in pesticide use due to Bt cotton cultivation has led to an increase in minor pests, including the tobacco caterpillar, mealy bugs, thrips, aphids, leafhoppers, green stink bugs, and serpentine leaf miners. This increase in minor pests could disrupt the original trophic levels and have cascade effects in India.
  • Soil health. Genetically modified plants, through the products of introduced genes, modified rhizosphere chemistry, or altered crop residue quality, have the potential to significantly alter microbial dynamics, soil biodiversity, and essential ecosystem functions such as nutrient mineralization, disease incidence, carbon turnover, and plant growth. 
  • Gene flow to wild relatives. There is a potential for gene flow from Bt cotton to wild cotton species through cross-pollination, which could potentially impact their genetic diversity and evolutionary process.