Divergent Trends in Insect Disturbance Across Europe's Temperate and Boreal Forests.

Area of Science:

• Ecology
• Forestry
• Entomology

Background:

• Climate and land-use changes are altering forest insect herbivore interactions and biotic disturbance regimes.
• Understanding these complex, variable changes across host species, insect taxa, and feeding guilds is crucial.

Purpose of the Study:

• To analyze long-term trends (2000-2022) in European forest insect disturbance dynamics.
• To determine how disturbance varies with host trees, feeding guilds, latitude, and climate.
• To investigate synchrony in insect disturbance patterns.

Main Methods:

• Compiled annual forest insect disturbance records from 15 European countries (2000-2022).
• Analyzed 1361 time series for 50 herbivorous insect species.
• Tested for systematic changes, climatic/latitudinal variations, and inter-species synchrony.

Main Results:

• Borer disturbance predominantly affected gymnosperms (largely Ips typographus), while defoliators impacted gymnosperms and angiosperms more evenly.
• Borer impact on gymnosperms increased, while defoliator impact decreased in the 21st century.
• Disturbance was higher in warmer, drier conditions; significant synchrony was found within host types and feeding guilds.

Conclusions:

• Insect herbivory trends diverge temporally but are linked to climate conditions.
• Increasing gymnosperm disturbance may drive forest composition shifts towards broadleaved trees.
• Enhanced monitoring and research are vital to understand mechanisms and emerging threats in forest insect herbivory.