What can insect plagues on trees tell us about climate change?

In the Netherlands, there has already been a reporting point for insect plagues since 1946.

horse chestnut leaf miner attack

That was a long time before climate change became topical. These reports are invaluable. They are used to signal and analyse immediate and slow changes (including climate change) over time. The fact, for example, that the oak procession caterpillar is slowly but surely moving northward is of vital importance for understanding our climate and the changes that are taking place.

There are currently approximately 400 conservationists who collect data about insect plagues in Dutch forests and cities. This data is invaluable, particularly now it has become evident that precisely in recent decades many immediate and slow changes have occurred within the populations. The data that is collected is, amongst other things, used to advise the Commission of Forest Protection about combating plagues. This might involve an ad hoc solution, but also a gradual change of a modified forest policy.

Endemic plagues

The network of conservationists are in close contact with this research project. The database that has been built up since 1946 is a necessary instrument in order to signal and analyse immediate and slow changes over time. The insight into the occurrence of plagues provides “fertile ground” for a policy strategy to be drawn up. It has been signalled that undesirable introductions from other continents will occur. Some exotic species can cause acute problems which require rapid intervention. An intensification of endemic plagues has also been seen. However, the data also shows slow shifts, such as the slow move northward of the oak procession caterpillars.

Nature conservationists

Researchers attempt to find backgrounds in order to be able to clarify the facts. Is it correct that insect plagues are occurring ever more frequently? Why is that? Is that because of the role of nitrogen deposition, climate change or land use? How can policy be developed to prevent or manage plagues of some exotic species? Not only are the results of this research used to develop policy, but also to provide advice, for purposes of clarification and for intervention where required. Furthermore, the database acts as a type of help desk for nature conservationists.