Spruce bark beetle outbreaks and climate change on the Kenai Peninsula, Alaska
Berg EE and De Volder AD. 2000. Spruce bark beetle outbreaks and climate change on the Kenai Peninsula, Alaska. US Fish and Wildlife Service
The climate of the Kenai Peninsula is changing dramatically. Glaciers have been retreating since the 1850 s and more rapidly since the 1970 s. Treeline is rising. Black spruce is invading wetlands. Kettle ponds have dried up since 1950, and closed basin lake levels show as much as 1-m decline within the last five years. A massive outbreak of the spruce bark beetle (Dendroctonous rufipennis Kirby) has killed most of the mature white and Sitka/Lutz spruce in the Kenai Peninsula forests, affecting 2-3 million acres over the last ten years. Widespread tree death has thinned forest canopies and released growth in survivors. We used dendrochronology to identify previous periods of canopy thinning in 17 widely distributed stands in the Kenai - Cook Inlet area. We find tree-ring evidence of regional spruce bark beetle outbreaks in the 1810 s-1820 s, 1870 s-1880 s, and 1970 s. The outbreaks of the 1970 s and 1990 s are strongly associated with drought stress, as warmer air temperatures have increased evapotranspiration and hence tree susceptibility to beetle infestation. We compare past outbreaks with reconstructed summer temperatures (to 1706) and find that at least two warm summers are required to initiate a spruce bark beetle outbreak. A string of warm summers since 1987 has allowed the beetles to exhaust most available host material.
- Type
- Published Report
- Authors
- Berg, Edward; De Volder, Andrew
- Date of Issue
- 2000
- Publisher
- US Fish and Wildlife Service
- Units
- KEFJ
- Keywords
- climate warming, Dendroctonous rufipennis, drought stress, growth release, Integrated Pest Management, Kenai Peninsula, spruce bark beetles