Intensive agriculture reduces the number of butterfly species: two-thirds fewer butterflies
Compared to areas in nature reserves, there are not even half as many butterfly species in meadows with adjacent intensive agriculture. The number of individuals even drops to one third. This is shown by the studies of a research team led by Jan Christian Habel from the Technical University of Munich (TUM) and Thomas Schmitt from the Senckenberg Nature Research Society.
Some 33,500 insect species are native to Germany - but their numbers are steadily declining due to widespread intensive agriculture. Of the 189 butterfly species currently found in Germany, 99 species are on the Red List, five species are already extinct, and a further 12 species are threatened with extinction.
In Switzerland, the situation is not far different as far as the impact of intensive agriculture on insects is concerned. Prof. Jan Christian Habel from the Chair of Terrestrial Ecology at the Technical University of Munich and Prof. Thomas Schmitt, Director of the Senckenberg German Entomological Institute in Müncheberg, Brandenburg, have worked in their teams to examine how the intensity of agricultural use specifically affects the butterfly fauna.
Reduced biodiversity in the vicinity of sprayed fields
For this purpose, the researchers recorded the occurrence of butterfly species on 21 meadow areas east of Munich. Seventeen of these areas are located in the middle of agricultural land, four in nature reserves managed in a near-natural way. The entomologists counted a total of 24 butterfly species and 864 individuals in all areas.
"On the meadows within the agricultural fields, we found an average of 2.7 butterfly species per visit; on the four study sites within the two protected areas "Dietersheimer Brenne" and "Garchinger Heide", the average was 6.6 species," adds Prof. Werner Ulrich from Copernicus University in Thorn, Poland.
Especially the specialists among the butterflies, which depend on the near-natural areas, suffered from the new conditions. The group also found more adaptable animals on the other grassland plots.
Negative effects of industrialized agriculture require rethinking
"Our results show a clear trend: near intensively cultivated, regularly sprayed fields, the diversity of butterflies and their numbers is significantly lower than in meadows near little to unused land," says the study's lead author, Dr. Jan Christian Habel
"Our study underscores the negative impact of industrialized conventional agriculture on butterfly diversity and shows that more environmentally sound farming methods are urgently needed. Further on-site investigations can also help to identify individual factors responsible for insect mortality and counteract them accordingly," concludes Schmitt.
Publication: J.C. Habel, W. Ulrich, N. Biburger, S. Seibold, and T. Schmitt
"Agricultural intensification drives butterfly decline"
Insect Conserv Divers, Feb. 7, 2019 DOI: 10.1111/icad.12343
Link: https://doi.org/10.1111/icad.12343
