Bark beetle damage in West slowing down; eastern pest-related deaths remain low
The number of dead trees on 750 million acres of public and private forests across America is on the decline for the second straight year, with most of the reductions seen in western states where bark beetles have infested millions of trees, according to a report released today by the U.S. Forest Service.
The report, Major Forest Insect and Disease Conditions in the United States: 2011, shows that damage caused by the mountain pine beetle is on the decline largely because the insect is running out of its favorite food source: lodgepole pine. Acres of forests with dead trees due to the mountain pine beetle declined from 6.8 million acres in 2010 to 3.8 million acres in 2011 in western states.
"Native insects and diseases run in cycles, and right now we are grateful the trend is downward," said U.S. Forest Service Chief Tom Tidwell. "While the news is good, we are certain to continue to face challenges, such as the effects of climate change and the introduction of invasive species. We must manage our lands across all boundaries to ensure the vitality and health of our natural resources."
This marks the second straight year with reduced mortality rates after steady increases between 2006 and 2009. Although Forest Service surveyors attribute some of the reductions to fewer available lodgepole pines, ponderosa pine and high-elevation white bark pine are still at risk.
“Forests play a crucial role in the lives of Americans by maintaining the quality of the environment and contributing to the quality of their lives,” said Agriculture Under Secretary Harris Sherman. “Healthy forests clean the air, filter our water, give homes to wildlife and provide recreation, jobs and materials for a healthy community and economy.”
The mountain pine beetle is not alone in its attack on forests. The spruce beetle, the most significant natural enemy of the mature spruce, has caused four consecutive years of increased mortality with dead spruce trees found on 428,000 acres nationwide. The fir engraver, common in western coniferous forests, is responsible for tree deaths on approximately 323,000 acres, most of which are in California. Death of subalpine fir, caused by bark beetles and other mortality agents, was found on more than 274,000 acres.
In the East, tree mortality due to insects and disease continue to remain low, with southern pine beetle-caused mortality at historically low levels. The southern pine beetle outbreak in New Jersey declined from 14,000 acres in 2010 to about 6,700 acres in 2011. However, that lower number of acres is still considered very high for New Jersey. Invasive forest diseases and insects, such as the emerald ash borer and the Asian long-horned beetle remain a big threat to eastern forests.