A 20-year analysis of U.S. forest health data reveals a clear signature of climate change in insect damage patterns.
A study published in Nature Ecology & Evolution analyzed 20 years of USDA Forest Service Insect and Disease Survey data (2000–2019) across the conterminous United States, examining forest damage from 30 high-impact insect species including emerald ash borer, mountain pine beetle, and hemlock woolly adelgid.
Key Findings
Maximum summer temperature and the rate of warming relative to a historical baseline were the most consistent climate signals associated with damage.
Damage was highest in regions with moderate maximum temperatures and accelerated warming. The relationship between climate and damage varied between bark beetles and defoliators, and between native and non-native species, as well as between western and eastern US regions.
For several species, the rate of warming was a stronger predictor of damage than absolute temperature. Warmer winters in the Great Lakes region were associated with increased survival and spread of emerald ash borer.
Methodology
The team used aerial detection records with damage polygons coded by pest species, and tested five bioclimatic variables: temperature, precipitation, and historical anomaly variables.
Context
Two related studies published in late 2025 and early 2026 documented increasing tree mortality in Australia and rising costs of climate-driven forest disturbances in Europe.
The authors concluded that climate change has already exacerbated pest performance and that future damage is projected to increase as temperatures continue to rise.