Pesticides impact on biodiversity


Cotton represents only 2.4% of the world’s arable land, yet it accounts for an average of 11% of global pesticide sales and 24% of the global insecticides market. This disproportional use of pesticides for cotton cultivation raises concerns about its impact on biodiversity. 

Insecticides are chemicals specifically designed to kill, harm, repel, or mitigate one or more species of insects. They work in various ways, such as by disrupting the nervous system or damaging exoskeletons. In cotton farming, insecticides such as organophosphates (e.g., parathion, malathion, fenthion, fenitrothion, diazinon, naled, methyl parathion, and dichlorvos) and carbamates (e.g., carbaryl, methomyl, propoxur, and carbofuran) are commonly used. Additionally, pyrethroids and neonicotinoids, which are used in cotton farming, have been found to pose risks such as insect resistance and toxicity to beneficial insects like bees. 

Rodenticides are pesticides used to kill rodents, and their use can have unintended impacts on non-target animals. Anticoagulant rodenticides, for example, can lead to secondary poisoning in wildlife when predators or scavengers consume poisoned prey. This can have detrimental effects on species such as birds of prey and mammals. 

Fungicides are used to control fungi that damage plants, but studies have shown that synthetic fungicides can have negative effects on biodiversity. For instance, tebuconazole, a commonly used fungicide in agriculture, has been reported to reduce soil microbial biomass and activity, which can have broader ecological consequences. 

Herbicides, used to control undesirable vegetation, such as trifluralin and pendimethalin, are commonly used in cotton fields. While effective, these herbicides can alter vegetation structure and reduce food sources for birds, insects, and mammals, potentially leading to changes in habitat suitability for certain species.

Pesticides are having a significant impact on biodiversity in a variety of ways, often caused by their misuse or overuse, as well as a lack of systematic control and understanding of ecosystem interconnections. Even without direct application to non-target organisms, pesticides are able to contaminate various components of the ecosystem, affecting them on different levels. 

Soil: Pesticide residues in soil can come from different sources, such as sprays or dusts from application onto foliage, insecticides applied directly to the soil, or seed coatings. In some cases, pesticides can leach below the root zone of treated plants. While pesticides can break down in the soil through microbial degradation, they can also harm the beneficial organisms needed to sustain a healthy soil ecosystem. The persistence of pesticide residues in soil depends on factors such as soil type, formulation, concentration, moisture, temperature, and pH, with half-lives ranging up to 7000 days.

Water: Pesticides, due to their high mobility, can contaminate surface and groundwater, affecting water sources for several months after application. 

Air: Pesticides sprayed on cotton fields can lead to air contamination as particles are carried by wind and air flow, impacting a wide range of ecosystems. 

Affected Organisms: 

Exposure of systemic insecticides to non-target organisms can occur via contaminated soil, water, and air using multiple exposure routes. Potential exposure from systemic pesticides applied to soil includes runoff or erosion of soil residues onto surface water and/or uptake into plants, from residues in the soil to pollen, nectar, and other exuded substances. 

Soil microorganisms: soil bacterias and fungi, including mycorrhizal fungi, involved into nitrogen fixation and organic matter decomposition, can be harmed reducing the soil fertility and health.

Invertebrates: earthworms, nematodes, arthropods, like beetles, ants, spiders can be reduced in the population, leading to disrupting their roles in the soils ecosystem.

Managed and Wild Bees: Bees are exposed to systemic pesticides through contaminated pollen, nectar, and guttation droplets from plants, affecting their health.

Other Beneficial Insects: Ladybugs, beetles, and predators of agricultural pests are negatively affected by systemic insecticides, impacting ecosystem diversity and natural pest control. 

Aquatic Organisms: Systemic insecticides can be highly toxic to juvenile carp and can impact zooplankton, bottom-dwelling, and water surface aquatic communities. They can also impair the growth of Japanese rice fish. 

Birds: Some species of birds are exposed to pesticides through ingestion of treated seeds or granular pesticides. 

Mammals: Pesticides can have long-term and short-term effects on mammal populations by impacting food webs. 

Human Health: Excessive pesticide use in agriculture can result in health issues for farmers, including acute symptoms such as eye irritation, skin problems, and respiratory issues, as well as potential long-term health risks. 

Initiatives and NGOs are working to control and minimize pesticide use in the textile industry, particularly in cotton farming, by encouraging proper pesticide use and training farmers in organic farming practices. However, the impact of pesticides on biodiversity is recognized as requiring further action and monitoring.