budworm

Weather appears to be a critical factor in determining budworm distribution.

Climate change and insects as a forest disturbance in the Arctic 2009

Populations of budworm have persisted in this area near the Arctic Circle, including a minor outbreak in 2002 – 2003.

Climate change and insects as a forest disturbance in the Arctic 2009

Irruptions of budworm generally follow drought, and outbreaks also start after hot, dry summers [19].

Climate change and insects as a forest disturbance in the Arctic 2009

The absolute distribution limits of spruce budworm generally follow that of white spruce throughout the boreal forest, and there are records of severe defoliation within 150 km of the Arctic Circle [16].

Climate change and insects as a forest disturbance in the Arctic 2009

Elevated summer temperatures increase budworm reproductive output.

Climate change and insects as a forest disturbance in the Arctic 2009

In that year, after a series of warm summers, a spruce budworm irruption occurred in the Bonanza Creek Long-Term Ecological Research site and visible canopy damage spread over tens of thousands of hectares of nearby white spruce forest.

Climate change and insects as a forest disturbance in the Arctic 2009

Before about 1990, spruce budworm had not appeared able to reproduce in the northern boreal forest of central Alaska.

Climate change and insects as a forest disturbance in the Arctic 2009

Finally, higher temperatures and drought can shift the timing of budworm reproduction so that natural parasitoid predators are no longer effective in limiting budworm numbers [22].

Climate change and insects as a forest disturbance in the Arctic 2009

Conversely, cold weather can stop a budworm outbreak.

Climate change and insects as a forest disturbance in the Arctic 2009

These include spruce budworm, forest tent caterpillar, jack pine budworm (Choristoneura pinus pinus), and gypsy moth (Lymantria dispar).

Climate change and insects as a forest disturbance in the Arctic 2009