Expanding Spruce Beetle Outbreak

According to a recent Denver Post article, an annual aerial survey of forest health in Colorado shows the mountain pine beetle epidemic is slowing dramatically, but the spruce beetle outbreak is expanding. The mountain pine beetle epidemic has spread by 31,000 acres, down from an increase of 140,000 acres reported last year, the U.S. Forest Service and Colorado State Forest Service said. Since the first signs of the outbreak in 1996, the infestation has grown to nearly 3.4 million acres, or roughly 5,300 square miles. The infestation remains active from Estes Park to Leadville. Meanwhile, the spruce beetle outbreak spread to 183,000 new acres in 2012, bringing the total infestation since 1996 to about 924,000 acres. The most significant spruce beetle activity has been in southern Colorado in the San Juan and Rio Grande national forests, forest officials said. Spruce beetles typically attack spruce trees downed by high winds, then move into the surrounding trees as the insects' numbers grow. Beetle activity has increased as trees have been stressed by factors including dense stands of trees, ongoing drought, and warmer winters that haven't been killing off as many insects. 

Beetle kill has the potential to affect water quality and quantity because the decrease in forest canopy due to defoliation results in decreased precipitation interception and decreased summer evapotranspiration.
It is possible that a massive die-off of infested trees could precipitate changes in water chemistry, including increased sediment loads and increased biomass in watersheds. One specific problem is increased organic carbon levels, which typically necessitates additional treatment before it can be consumed by humans. Brent Ewers, an associate professor of botany at the University of Wyoming, told the Associated Press that when infected trees fall, snowpack decreases due to increased wind and lack of shade.