‘We have over 350,000 kilometres of ditches in the Netherlands. That's why we have perfect conditions for agricultural practices, and that's why you can live here’, says Martina Vijver, Science director and Professor of Ecotoxicology at the Institute of Environmental Sciences (CML) at Leiden University.
Nearly a third of the Netherlands lies below sea level, so canals and ditches play a key role in water management. They also provide valuable habitat for aquatic species. Vijver, along with Marco Visser, a theoretical ecologist and Assistant Professor at the CML, recently updated the Pesticide Atlas. This interactive website makes data about pesticide concentration in surface waters available to the public. This year, instead of looking at pesticides individually, the researchers examined the toxic effect combinations of pesticides have on aquatic life.
‘If we talk about pollution, the simple questions should be: Where is it? What is it? How much is there? ‘says Vijver. ‘Pesticide measurements are very expensive and you as a citizen are paying for that via taxes. We wanted to have all those precious measurements on surface water not just stored away by the water boards, but available for everybody.’
Responsible for your own house
‘Authorization of pesticides is based on single compounds, which is very normal. To explain with an analogy: you are responsible for your house and not for the neighbour’s. If you manufacture a chemical, then you want to be regulated and evaluated based on what you make’, says Vijver.
However, there are weaknesses to assessing pesticides individually. Taking the perspective of a water-dwelling creature helps show why. According to Visser, ‘the protection norms have the idea of providing some kind of basic safeguard for the ecosystem. And what we see is that quite frequently, all the substances are under the norm. But combined, they exceed the desired protection level and hence those individual norms aren't protecting nature which is exposed to all chemicals and stressors at once.
‘Aquatic and terrestrial life are beautiful, and we’re ruining it’, says Vijver. According to Visser, ‘the online atlas not about responsibility or assigning blame. This is about quantifying risk. ‘He draws attention to the diversity of life that is impacted by the presence of pesticides, which includes ‘anything that depends on water for one part of its life cycle. ‘This includes microbes, fungi, algae, plants, invertebrates, fish, and amphibians, among others.
Pesticides aren’t made to be put in the water. They simply end up there as a matter of content. ‘I start with households because if you have a cat or a dog then you will use anti-flea stuff’, says Vijver. ‘You give the animal a pill or droplets and then it is protected against fleas for the next 4 weeks. The medication is then in all tissues of the animal, but also all the hairs will contain those residues. So if the animal loses hair in the environment, the chemicals will end up in the environment.
‘Obviously, pesticides are also used by farmers. They can spray or use it as seed coating for plants and then it can end up in the water. It can also leach off from the soil. If you use it as municipalities to clean up your pavements, it also will run off to the water. ‘
Visser points out another, often forgotten emission route. ‘A lot of these pesticides are volatile chemical compounds. They evaporate and then, just like rain, when the atmospheric conditions reach the dew point temperature for these chemicals, they condense and precipitate back to the ground.’
new bag of tools
Now that the findings are publicly available, what happens next is largely out of Vijver and Visser’s hands. But Visser says the new data will ‘give policymakers a whole new bag of tools’.
Accessibility is particularly important to Visser. ‘One of the key things our pesticide atlas does is provide a common truth for societal debate, and that's our ambition: to provide a common truth. Anybody can, from their own agenda, interpret things differently, but if we can at least agree on the numbers. Then we then we have some common truth which to base consensus about.’
Vijver hopes the data will lead to ‘a transparent debate based on facts. Because if you know the degree to which compounds are contributing to toxicity, or you know which compounds exceed the protection norms the most, then you can talk with sectors that use it – which can also be household emissions. The data can enable informed dialogues about responsibility and remediation.’
Clean water
There is also a long-term goal to this research. ‘I think the other thing we should really think about is preserving the quality of water and the quality of our groundwater for future generations’, says Visser. ‘We believe that aquatic life should be guaranteed in the Netherlands. Clean water with abundant aquatic life is healthy water.’
‘We always think about ourselves and whether we might be polluted’, sats Vijver. ‘But we don't think about who we pollute. If we don't have aquatic life, we won’t exist either.’