The forest as a warm shelter for insects

About 75% of our food crops and more than 80% of wild plants require insect pollination. The value of crop pollination alone is estimated at US$577 billion per year worldwide. The best-known pollinators are bees, but they are by no means the only insects that perform this service for man and nature – flies, wasps, beetles, butterflies and moths also play a role. important.

Several studies have identified a significant decline in insect populations over the past decades – also in Germany. So far, the focus has been on the loss of suitable insect habitats; for example, the conversion of natural spaces into agricultural or urban spaces. But what are the consequences of land use in combination with hotter and drier climates for pollinating insects? And what could be done to mitigate possible negative consequences? This has been investigated in a new study from Julius-Maximilians-University (JMU) Würzburg.

The main conclusions of the study

The JMU research team and collaborators reveal for the first time how climate and land use together shape the diversity of pollinating insects at local and landscape scales across Bavaria. Based on more than 3200 pollinator species identified from 179 sites in forests, grasslands, arable and urban habitats, they find a homogenization of pollinator communities in warmer climates. This suggests an overall loss of pollinator diversity under future climates.

Individual taxa such as bees, flies, beetles, butterflies and moths showed different responses to warmer and drier climates, but the general pattern indicates that landscapes with higher proportions of forest maintain communities more diverse pollinators. “A key finding, then, is that forest in the landscape can buffer the effects of global warming to some extent.” explains Cristina Ganuza, a doctoral student in the group of Professor Ingolf Steffan-Dewenter in the Department of Animal Ecology and Tropical Biology at JMU, and lead author of the study.

“The study highlights that in addition to the importance of floral resources and the negative effects of land use intensification, climatic conditions play an increasingly important role in maintaining pollinator diversity. . For example, the combination of high temperatures and low precipitation had a negative effect on total pollinator diversity, while bee richness in urban areas was negatively affected by higher average temperatures,” says Steffan-Dewenter. .

Relevance to nature and humans

A high diversity of pollinators is necessary for high pollinator performance. Ganuza: “However, the combination of ongoing climate change and current land use will only allow certain species of pollinators to survive in different types of habitats.”

“We conclude that much of the forested land in the landscape could serve as a refuge for insects from global warming,” Ganuza said. “This is likely because forests and forest edges provide largely natural conditions that buffer extreme heat and drought compared to more human-influenced habitats.”

Another suggestion from the researchers would be to lower the air temperature in cities, for example through greening. “This could allow more species of bees to live in urban areas,” explains the biologist. In short, insects love diversity. And flowering plants as diverse as possible are essential for small animals in all areas.

Cooperation partners and funding

The JMU study was recently published in the journal Scientists progress. It was realized in cooperation with the University of Bayreuth, the Technical University of Munich and the Weihenstephan-Triesdorf University of Applied Sciences. It was funded by the Bavarian Ministry of Science and Arts as part of the Bavarian Climate Research Network in the research group “LandKlif – Impacts of climate change on biodiversity and ecosystem services in semi-natural landscapes, agricultural and urban and strategies for climate change management” (


Ganuza et al: “The interactive effects of climate and land use on pollinator diversity differ across taxa and scales”; in: scientific progress; doi: 10.1126/sciadv.abm9359


Cristina Ganuza, Department of Animal Ecology and Tropical Biology, University of Würzburg Biocenter, T. +49 931 – 31 86893, [email protected]

Sarah Redlich, Department of Animal Ecology and Tropical Biology, University of Würzburg Biocenter, T. +49 931 – 31 821290,

Ingolf Steffan-Dewenter, Department of Animal Ecology and Tropical Biology, University of Würzburg Biocenter, T. +49 931 – 31 86947,

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