Insects in the light of land use and climate – sciencedaily
Globally, the quantity and diversity of insects is decreasing: scientists have reported more and more evidence of this in recent years. In politics and in society, these findings have given rise to great concern.
The researchers attribute the decline in the number of insects on the one hand to changes in land use, for example to the increase of large monocultures such as maize and rapeseed, but also cite climate change with the increase in temperatures and drought as the cause.
Previous data has weaknesses
However, these results appear to have weaknesses, explains Professor Jörg Müller, animal ecologist at the Julius-Maximilians-Universität Würzburg Biocentre (JMU) in Bavaria, Germany. Among other things, the underlying studies so far either do not represent the diversity of insect species well enough or only consider short periods of time and small areas.
A research team from the Bavarian LandKlif The network, coordinated by JMU, now wanted to remedy this shortcoming. The results of the study were published in the journal Nature Communication. They show that urbanization is another key factor in the global decline of insects.
Study on 179 sites from low to high altitude
From Lower Franconia to Upper Bavaria, researchers placed traps to collect flying, crawling and jumping insects in the spring of 2019. These Malaise traps were located at 179 sites, from plains at altitudes above 1,100 meters in the forest Bavarian and the Alps. They were located in forests, meadows and fields as well as in settlements, embedded in semi-natural, agricultural and urban landscapes.
The researchers emptied the traps every 14 days for an entire growing season. They determined the biomass of captured insects and identified individual species using DNA sequencing.
Insects benefit from higher temperatures
“In this study, we were able for the first time to disentangle the impact of climate and land use on insects in a central European landscape,” explains Jörg Müller. “It is interesting to note that the temperature at the local site as well as the annual temperature only have positive effects on the biomass and the diversity of the insect populations. The form of land use, on the other hand, has different effects on biomass and diversity. “
“We observed the greatest difference in insect biomass between semi-natural and urban environments. In the city, the biomass was 42% lower. Insect diversity was 29% lower in agricultural environments compared to semi-natural habitats. There were even 56% fewer endangered species in agricultural areas, ”explains Johannes Uhler, JMU doctoral student and first author of the study.
Consequences for the conservation of insects
“These contrasting patterns of biomass and species diversity are an important warning sign for researchers,” Uhler sums up: for insect monitoring, one should not conclude that a decline in biomass also means a decline in the diversity of species, and vice versa.
Based on his new findings, JMU researchers recommend creating more green spaces in urban settings to increase insect biomass. Existing agri-environmental programs should be further extended to improve biodiversity and forest habitats should be promoted.
The LandKlif research network
Created in 2018, the Bavarian LandKlif The research network is active in the semi-natural, agricultural and urban landscapes of five climate zones in Bavaria – from the hot and dry regions of Lower Franconia to the high altitudes of the Bavarian Forest and the Berchtesgaden National Parks. Its objective is to identify options to mitigate climate change and adapt to changing climatic conditions. The network coordinator is Prof. Ingolf Steffan-Dewenter from JMU Biocentre. The Free State of Bavaria is funding the network with 2.6 million euros.
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Material provided by University of Würzburg. Original written by Robert Emmerich. Note: Content can be changed for style and length.