Citizen scientists, dragonflies and pesticides

Citizen scientists, dragonflies and pesticides

Water quality has improved quite a lot in the second half of the last century and dragonflies, as aquatic insects, have recovered in this period. However recently we have seen that numbers have started declining again and this seems to be mostly the case with the common species outside of nature reserves. We know this because there are hundreds of volunteers counting dragonflies every two weeks on fixed transects. By comparing the number of dragonflies that are counted we can see how different species are doing in different locations. Even some of the least critical species seem to be disappearing from certain parts of the Netherlands. Why this is happening is unknown. For other groups of aquatic insects we do not have detailed information but they seem to be following a similar pattern.
Dragonflies can therefore be used as a flagship species for aquatic biodiversity.
Within ACTION we want to figure out if pesticides play a role in this decline. We know from a very recent study that, even at levels regularly found in ditches, a specific insecticide can have strong negative effects on damselflies.
As the trends in dragonflies on the monitoring transects are known, thanks to the citizen scientists, we can therefore study this in natural populations. By taking water samples and measuring the pesticide concentrations we can see whether the trends in dragonflies reflect the exposure to pesticides. We also have data from people recording dragonflies and we can use this to estimate the distribution. This will be compared to modelled pesticide levels in surface waters in The Netherlands. Together this will give insight in to what extent pesticides are a threat to dragonflies and which pesticides are most harmful.

Contact: Roy van Grunsven, De Vlinderstichting

Citizen scientists, dragonflies and pesticides

Water quality has improved quite a lot in the second half of the last century and dragonflies, as aquatic insects, have recovered in this period. However recently we have seen that numbers have started declining again and this seems to be mostly the case with the common species outside of nature reserves. We know this because there are hundreds of volunteers counting dragonflies every two weeks on fixed transects. By comparing the number of dragonflies that are counted we can see how different species are doing in different locations. Even some of the least critical species seem to be disappearing from certain parts of the Netherlands. Why this is happening is unknown. For other groups of aquatic insects we do not have detailed information but they seem to be following a similar pattern.
Dragonflies can therefore be used as a flagship species for aquatic biodiversity.
Within ACTION we want to figure out if pesticides play a role in this decline. We know from a very recent study that, even at levels regularly found in ditches, a specific insecticide can have strong negative effects on damselflies.
As the trends in dragonflies on the monitoring transects are known, thanks to the citizen scientists, we can therefore study this in natural populations. By taking water samples and measuring the pesticide concentrations we can see whether the trends in dragonflies reflect the exposure to pesticides. We also have data from people recording dragonflies and we can use this to estimate the distribution. This will be compared to modelled pesticide levels in surface waters in The Netherlands. Together this will give insight in to what extent pesticides are a threat to dragonflies and which pesticides are most harmful.

Contact: Roy van Grunsven, De Vlinderstichting

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