Banned pesticides for decades, such as DDT, and heavy metals like mercury, were found in the feathers of white storks nesting in Galicia, Spain. Through a project led by researchers from the University of Santiago de Compostela, the impact of invisible contaminants on these birds that roam agricultural fields in search of food was analyzed.
The study focused on feathers and pellets collected from 23 nests distributed in 10 Galician localities. There, 11 different pesticides were detected, seven of which are already banned due to their persistence in the environment. The majority of the detected toxins, 83.3%, correspond to products that are no longer in legal use, demonstrating their high stability in ecosystems.
Residues of herbicides such as atrazine —banned in the European Union since 2004— and highly toxic compounds like DDT or dieldrin were also identified, still present in low concentrations. Their accumulation is concerning, as they can reactivate and re-enter food chains through soil disturbance or atmospheric circulation.
Mercury and pesticide residues were found in stork feathers. Photo: Pixabay.
The countryside as a mirror of environmental contamination
One of the most striking conclusions is that contaminants vary depending on the type of crop. In potato or maize areas, storks had a different chemical profile than in regions with livestock or orchards. This suggests a close relationship between land use, agricultural production, and the exposure of wildlife to dangerous substances.
The study demonstrates that storks, as they move and feed in different rural environments, become excellent biological indicators. They not only show the effects of plastics already found in their nests and digestive tracts but now also reveal the persistence of invisible substances that remain active in soils and the air.
In some areas, such as Monforte de Lemos and Maceda, up to seven different banned pesticides were recorded, raising concerns about possible unauthorized uses. In turn, mercury was most frequently detected in regions with intensive agriculture, decreasing in traditional livestock areas.
Storks as an example of environmental damage
These birds are not only witnesses to a silent environmental problem but also allow tracing a map of historical contamination in rural environments far from industrial centers. Through the analysis of their feathers, the researchers managed to make visible what was previously hidden beneath the natural appearance of the fields.
Understanding the persistence of these toxins and their effects on wildlife is key to developing more effective environmental policies. The research emphasizes the need to strengthen pesticide use monitoring and promote responsible agricultural practices that protect both native species and the ecosystems they inhabit.
Stork. Photo: Pixabay.
The consequences of pesticide use
The use of pesticides in agricultural fields can have devastating effects on wildlife. These substances, designed to eliminate pests, do not distinguish between target species and others that live or feed in the same environments, affecting pollinating insects, birds, amphibians, and mammals.
The toxins can accumulate in the animals’ bodies, especially those at the top of the food chain. This not only causes health problems —such as reproductive or neurological issues— but can also jeopardize the survival of vulnerable species.
Moreover, chemical residues remaining in the soil or water indirectly affect entire habitats, disrupting the ecological balance. In this context, constant exposure to pesticides threatens biodiversity and reduces ecosystem resilience to climate change and other human disturbances.
