Grassland bird food supply could be under threat from pesticides

Researchers have found 129 different pesticides on 23 cattle farms in Gelderland that likely have a negative impact on grassland birds. The Buijs Agro-services and WECF Nederland research agencies published a report on this in 2019, and have recently extended this research in collaboration with Radboud University scientists, publishing their results in the journal Science of the Total Environment.

"In spite of all the protection programmes in the Netherlands, grassland birds are disappearing at an alarming rate. International research reveals that a shortage of food for chicks is a widespread reason that they die off both in Europe and in America," says Jelmer Buijs of Buijs Agro-services, a PhD candidate with environmental researcher Ad Ragas of Radboud University. "With this research, we show that pesticides could have a major negative impact on these food chains."

The researchers’ took samples of the soil, feed, litter and manure at the 23 Gelderland cattle farms, 22 of which are participating in the bird protection programmes. They found 129 different pesticides in total, with the total pesticide content in cattle dung at the eight organic farms 43% lower than on the 15 traditional livestock farms. However, this difference was not significant, partly as a result of the extremely large variation between the farms.

Effects on manure fauna and aquatic life

The chicks of grassland birds eat insects, such as dung beetles. The researchers observed that the more pesticides the livestock ingested, the fewer dung beetles there were in their manure in the fields. The researchers also estimated the quantity of pesticides introduced to the pasture through feed, litter, veterinary medications and manure. "If these estimates are compared with the European standards, it may be assumed that the food chains of the grassland birds on most of the cattle farms suffers as a result of the chemical substances encountered," Buijs says.

Where manure is spread over the land, some of it may end up in the surrounding ditches, for example as a result of incorrect spraying, run-off, drainage or pumping to lower the water table. This also applies to the pesticides in the manure. The researchers used calculations to show that the standards for certain pesticides are exceeded even when only a small amount of manure ends up in the ditch, whereas these standards are intended to protect aquatic life in the ditches.

"What we have also shown more especially is that large quantities of substances occur in low concentrations. In all the ecological tests that are conducted, one looks only at the risks resulting from individual substances, and not at the overall total of these substances, which turn into toxic cocktails," Buijs says. "We found up to 45 different pesticides in each manure sample."

Gaps in the knowledge

"This research’s added value lies in particular in the fact that we have laid bare a route for the distribution of pesticides that had previously received scarcely any attention," Ad Ragas says. Partly in response to this report in 2019, the Louis Bolk Institute detailed the gaps in the knowledge for the Agriculture, Nature and Food Quality Ministry (LNV). LNV Minister Staghouwer recently tasked the RIVM with conducting research into pesticide concentrations in manure.

Literature reference

Presence of pesticides and biocides at Dutch cattle farms participating in bird protection programs and potential impacts on entomofauna, Jelmer Buijs, Ad Ragas, Margriet Mantingh, Science of The Total Environment. DOI: 10.1016/j.scitotenv.2022.156378

Contact information

For further information, please contact Jelmer Buijs (%20jelmerbuijs [at] (jelmerbuijs[at]gmail[dot]com)), Ad Ragas (a.ragas [at] (a[dot]ragas[at]science[dot]ru[dot]nl)) or team Science communication via +31 24 361 6000 or media [at] (media[at]ru[dot]nl).   

Organizational unit
Environmental Science
Sustainability, Nature