The field cricket - the Dutch insect of the year 2024 - has been going downhill in recent years. Research by Joost Vogels of Radboud University, the Bargerveen Foundation and research centre B-WARE shows that this is mainly due to an excess of nitrogen. Measures to remove nitrogen are counterproductive.
Field crickets live mostly in moorlands. Previous research has shown that heather plants contain increasing amounts of nitrogen. Ecologist Vogels: ’Because other elements such as phosphorus do not rise along with that nitrogen, an imbalance is created in the plants. That affects animal species that have to live off it, because they desperately need phosphorus, among other things.’
Measures taken to remove accumulated nitrogen, such as ploughing the soil and spreading lime, can cause the proportions to go even further out of balance. Vogels: ’Soil ploughing removes nitrogen, but also phosphorus. And spreading lime reduces the availability of other trace elements that are crucial for animal species, such as sodium and manganese.’
Extra phosphorus
In field and food experiments, Vogels looked at how this imbalance affected field cricket growth and reproduction. ’We saw that crickets that were fed extra phosphorus, for example, grew better and had more offspring. Moreover, we showed that the right nitrogen-to-phosphorus ratio meant that almost all’essential elements were better absorbed by the crickets’, explains the ecologist. However, when an area was limed, all these positive effects were wiped out. ’Liming causes a shortage of manganese, which is essential for nutrient development. We even saw that females -very unnaturallystarted cannibalising on the males just to take in enough essential nutrients.’
The researchers stress that the only sustainable solution for protecting Dutch biodiversity is to reduce nitrogen deposition. Vogels: ’We have to start pushing for a source-based approach. Only then can we restore biodiversity.’
Literature referenceNitrogen deposition and heathland management cause multi-element stoichiometric mismatches, reducing insect fitness https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2435.14671
