New study finds crop residue burning disrupts biodiversity and weakens farm ecosystems.
Natural predators such as spiders, ladybirds and frogs decline sharply after burning.
Soil health deteriorates due to higher temperatures, nutrient loss and reduced microbes.
Air pollution from burning harms beneficial insects and bird species.
The cascading impacts increase pests and chemical fertiliser dependence in agriculture.
While the air pollution impacts of crop residue burning are well known, a new study has found that the practice also has severe consequences for agroecological biodiversity, driving pest outbreaks in agricultural fields.
The study, published in the journal Science of the Total Environment, reported that burning crop residue depletes soil nutrients, undermining long-term productivity. The air pollution released during the process also disrupts the ecological functions of arthropods and birds, it noted.
The findings are based on a qualitative systematic review of 250 peer-reviewed studies, focusing on the direct effects of residue burning, its air pollution impacts and consequences for arthropods and birds. The journals reviewed included studies from Asia, North and South America and Africa, covering countries such as Brazil, China, India, Mexico and Pakistan.
Arthropods, which form a dominant component of agroecosystems, provide crucial ecosystem services including nutrient cycling, pest control and soil aeration. But the study found that crop residue burning directly wipes out arthropod populations by directly killing them, leading to habitat loss and altering microclimatic conditions with sudden temperature rises.
For instance, natural predators such as spiders (Hippasa greenalliae), ladybird beetles, earwigs, predatory mites, beetles and frogs decline during the burning process, reducing species diversity and richness in plantations. Other decomposers, including sow bugs, red imported fire ants, aquatic mesofauna, millipedes and earthworms, also decline, impacting soil biodiversity.
These organisms play a crucial role in maintaining soil structure, controlling pests and improving nutrient cycles, the researchers noted. Their decline increases the prevalence of pests and parasites such as nematodes, mice and other organisms, disrupting natural pest control mechanisms. This makes crops more vulnerable to infestations and drives greater reliance on chemical-intensive farming.
Other insect orders affected include Hymenoptera (ants), Hemiptera (bugs), Lepidoptera (butterflies and moths), Diptera (flies and parasitoids) and Blattodea (cockroaches).
The researchers noted that burning raises soil temperatures to between 33.8°C and 42.2°C, causing nitrogen losses, declines in soil organic matter and reductions in microbial populations down to a depth of 2.5 centimetres.
Residue burning releases a range of air pollutants — including carbon monoxide, nitrous oxide, sulphur oxides, heavy metals, toxic compounds and particulate matter (PM) such as PM 2.5 and PM 10. This not only degrades air quality but also impairs the activity, reproduction and survival of beneficial arthropods, including pollinators.
Using the Secondary Evidence for Residue Burning approach, the researchers also found that birds — both generalist and specialist species that depend on insects for survival — are harmed by air pollution.
“Air pollution negatively affects birds through respiratory issues, which impact their reproductive success, thinning of eggshells, heavy metal contamination on feathers and other parts of the body, and also by reducing the availability of insects for them to feed on,” the authors said. They added that hatching success and juvenile development are also negatively impacted.
Residue burning reduces the availability of resources for arthropods, particularly insects, which in turn affects birds indirectly. With no safe spaces to hide, arthropods become exposed in open soil, making them easy prey for predators, leading to unsustainable predation.
Such processes undermine the sustainability of the food web, damaging organisms across trophic levels and eroding vital ecosystem functions, the study concluded.