Climate change could double spruce bark beetle generations and push spring a month earlier in Sweden
Langvall O, Strandberg G
Phenology
Bark beetles killing spruce trees across northern Europe are already a visible threat in many forests, and warmer summers letting them breed a second generation in one year could accelerate that damage well beyond what foresters currently plan for.
Scientists in Sweden tracked when birch trees leaf out, when bilberries ripen, and when a destructive forest beetle swarms, then built models to predict those timings using temperature data. They ran those models forward using climate projections and found that by 2070-2099, spring could kick off 9 to 41 days earlier depending on how much the planet warms. The most alarming finding is that the spruce bark beetle, which normally completes one life cycle per season, could routinely squeeze in two generations per summer in southern Sweden, meaning far more beetles attacking trees each year.
Key Findings
Broadleaf trees (birch) are projected to start the growing season 9-41 days earlier by 2070-2099 compared to 1970-1999, with the range depending on the emissions scenario (RCP2.6 vs. RCP8.5).
The European spruce bark beetle (Ips typographus) could produce two new generations per season by late century; in southern Sweden this may become the norm, while in the north it would occur only occasionally under the most severe warming scenario.
Southern Sweden and the maritime west coast are expected to experience the greatest phenological shifts, while northern Sweden and continental interior areas face the least change.
chevron_right Technical Summary
Swedish researchers built forecast models predicting when trees bud, berries ripen, and bark beetles swarm, then used climate scenarios to project how those timings will shift by century's end. Under the worst-case warming scenario, spring in Sweden's forests could arrive over a month earlier, and the destructive spruce bark beetle could complete two full generations per season instead of one.
Abstract Preview
Original paper
Short-term forecasts and long-term regional scenarios of climate change effects on Swedish forest phenology.
Comprehensive forest phenology data from the Swedish National Phenology Network has been used to produce forecast models of the seasonal phenology on tree species, wild berries and insects, which a...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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