Streams within approximately 40 percent of the global land surface are at risk from the application of insecticides, according to the first global map to be modelled on insecticide runoff to surface waters.
This has been found by researchers from the Helmholtz Centre for Environmental Research (UFZ) and the University of Koblenz-Landau together with the University of Milan, Aarhus University and Aachen University.
According to the findings, streams in the Mediterranean, Southeast Asia, the USA and Central America are particularly at risk. Agricultural pesticides are applied to help farmers control insects, weeds and other potentially harmful pests threatening agricultural production.
According to estimates, around four million tons of agricultural pesticides are applied annually, equating to an average of 0.27 kilograms per hectare of the global land surface.
"We know from earlier investigations for example that pesticides can reduce the biodiversity of invertebrates in freshwater ecosystems by up to 42 percent and that we can expect an increased application of pesticides as a result of climate change," said prof Matthias Liess from Helmholtz Centre for Environmental Research (UFZ), Germany.
Liess warned of an increase in the application of pesticides in many developing countries as farmers increasingly switch from traditionally extensive agricultural practices to more intensive ones.
Until now the global extent of the potential water pollution from the application of insecticides has largely remained unknown.
"In this respect, daily rainfall intensity, terrain slope and insecticide application rate play an equally important role as well as the crops cultivated," explained co-researcher Ralf B. Schafer from the University of Koblenz-Landau.
"Our analysis provides a global map of hotspots for insecticide contamination that are a major risk for biodiversity in water bodies," Liess said.
The researchers intend to use the global map to sensitise citizens and authorities about this issue in vulnerable regions and to incite local investigations.
For example: buffer zones along the edge of water bodies can significantly reduce negative impacts. Efficient environmental management and conservation efforts in the future should focus on informing authorities and farmers about the costs, impacts and alternatives.
The findings appeared in the journal Environmental Pollution.
