First global map shows water bodies on 40 percent of the world’s land area at risk from pesticide run-off.

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First map detailing run-off risk

However, until now the global extent of the potential water pollution from the application of insecticides has remained largely unknown. Prof Leiss’ team used data from the UN FAO, NASA and measurements from around 77,000 weather stations to establish ‘runoff potential’ (RP), in other words the amount of insecticides that are likely to enter streams at a given time, through rainwater from agricultural land.

“In this respect, daily rainfall intensity, terrain slope, and insecticide application rate play an equally important role as well as the crops cultivated", explained junior professor Dr. Ralf B. Schäfer from the University of Koblenz-Landau. “In order to test such complex models, we therefore carried out control measurements of insecticide contamination in freshwater ecosystems from four different regions.”

Several world maps were produced: the vulnerability map only takes into account the geographic and climatic background. The risk map on the other hand shows the risks from this natural vulnerability, by including anthropogenic land use (the way land is managed by humans).

In Central Europe, scientists largely assessed the risk for water bodies as medium to high. Elsewhere, the risk of insecticides posing a threat to water bodies was higher in Southern Europe. In the global North, the scientists found that, in general, the nearer to the equator an area is, the more likely it is there will be higher insecticide use, because of higher average temperatures.   

UFZ researchers said that their colleagues are investigating ways to mitigate the use of plant protection products, and so protect non-target lifeforms in environments that are at risk. They said that, in areas of south-east Asia where waterbodies were shown to be at risk, “One approach… could be to revitalise the functioning of ecosystems so that the natural competitors of rice pests can help to avoid their mass reproduction and subsequent harvest yield losses.”

Prof Leiss said, “Our analysis provides a global map of hotspots for insecticide contamination that are a major risk for biodiversity in water bodies. To our knowledge this is the first study that assesses insecticide contamination of water bodies on a global scale.”

The professor and his colleagues intend to use the map to drive action in vulnerable areas, from informing citizens to encouraging governments to investigate the issues in their territory. They said a variety of mitigation measures can be taken, including establishing buffer zones along the edge of water bodies.

Leiss' team recommended that “Efficient environmental management and conservation efforts… should focus on informing authorities and farmers about the costs, impacts and alternatives,” but said that, “Ultimately, mitigation and management takes place at the local level.”