Saturday, October 25, 2008

More than 10,000 oaks in San Diego County affected

I’m on a beetle kick today. Or maybe it’s the internet, not me. From Bugs and diseases are killing trees at an alarming rate across the West, from the spruce forests of Alaska to the oak woodlands near the San Diego-Tijuana border. Several scientists said the growing threat appears linked to global warming. That means tree mortality is likely to rise in places as the continent warms, potentially altering landscapes in ways that increase erosion, fan wildfires and diminish the biodiversity of Western forests.

It also could prompt new approaches to forestry. Possibilities include replanting logged areas with trees that are tolerant of higher temperatures, thinning drought-stressed forests and deploying pesticides to ward off insects. But in many cases, landowners have few options to protect their trees once insects and diseases take hold, tree experts said.

One serious problem is emerging in San Diego County. U.S. Forest Service officials recently announced that a newcomer called the gold-spotted oak borer has infested a larger area than they thought just a few months ago. The beetle could easily march north into more of the estimated 33 million forested acres statewide.

The pest already is blamed for killing more than 10,000 oaks in the county. Some backcountry residents fear the worst is yet to come unless the drought is broken by years of heavy rain, but that's unlikely to happen. Climate models show the Southwest becoming increasingly warm and dry over the next century, conditions that leave the Cleveland National Forest and others vulnerable.

Butterfield Stage Station, Oak Grove (San Diego County, California) (cropped). The oak in this picture is in danger

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