Neonicotinoids are nicotine-based chemicals that are the main ingredients in certain insecticides, and their use on a large scale is partly responsible for the alarming drops in the numbers of wild birds in various habitats in the US, according to a team from researchers from the University of Illinois.
Birds have not done well in the United States, and their numbers have dropped by nearly a third in just half a century. In the grasslands, meanwhile, their numbers have been cut in half.
Some scientists say they now know of one of the main reasons, which has been largely overlooked until now: the use of neonicotinoids.
Specifically, an increase in the use of neonicotinoid-based insecticides may be directly related to significant reductions in bird biodiversity between 2008 and 2014, particularly for grassland and insectivorous birds, scientists explain in one study.
Neonicotinoids have long been known to have a deleterious effect on wild bees, honey bees, butterflies, and other insects, but their impacts on birds haven't been studied in depth until the latest study, which is the first investigation. of this type conducted nationwide in the USA and took seven years to complete.
The scientists behind the study used data from hundreds of bird species in four different categories: grassland birds, non-grassland birds, insectivores, and non-insectivores.
“We found strong evidence of the negative impact of neonicotinoids, particularly in grassland birds, and to some extent in insectivorous birds after controlling for the effects of changes in land use,” explains Madhu Khanna, Distinguished Professor. of agricultural and consumer economics at the University.
A 100-kilogram increase in neonicotinoid use by county, representing a 12% increase on average, led to a measurable decline of 2.2% in grassland bird populations and 1.6% in grassland bird populations. insectivorous birds. In comparison, if 100 kilograms of non-neonicotinoid pesticides were used in a comparable area, only a 0.05% decrease was observed in grassland birds and only a 0.03% decrease in non-grassland birds, insectivorous birds, and birds. non-insectivorous. say scientists.
Worse: The damaging impacts of neonicotinoids add up over time, such that 100 kilograms of neonicotinoids used in a county in 2008 reduced cumulative grassland bird populations by 9.7% in the area in just six years to 2014 .
The implication is clear: Nicotine-based insecticides are a clear and present danger to wild birds.
Birds are likely to ingest the chemicals by feeding on seeds of crops treated with them and by feeding on contaminated insects. "Consuming a few seeds is enough to cause long-term damage to bird reproduction and development," say the authors.
Neonicotinoids are also more toxic to insects and persist longer in the environment, inflicting further damage to ecosystems. The solution is to phase out its use in favor of less toxic alternatives, experts say.