PubMed · 2026-07-06
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.
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.
