The Sensible Environmentalist

Forest Pests a Major Threat to Ecosystems

(NAPS)�DEAR DR. MOORE: I keep seeing forests that have turned brown from some kind of infestation. Is this common?

Unfortunately, yes. According to the US Forest Service, about 70 million acres are "at serious risk of being wiped out by 26 insects and diseases," some of which are native and some of which are introduced.

You�ve seen the impacts. Those brown forests represent a heartbreaking loss of biodiversity, not to mention cultural heritage. Thanks to Dutch elm disease, for example, the American elm has all but disappeared from the urban landscape, and white pine blister rust has pretty well obliterated the western white pine and American chestnut.

It�s been described as "catastrophic wildfire in slow motion," the way an infestation spreads across the landscape, killing an entire forest. And, as with fire, the best way to protect native forests is to prevent the pests from taking hold. Part of this includes actively managing our forests�by removing dead wood and undergrowth, and thinning the trees�to keep them healthy and able to resist attack.

The US Forest Service has a four-pronged strategy that begins with prevention, which makes sense, given that control efforts and economic damages are estimated to cost the US $137 billion every year. But consider the challenge. Most exotic pests are introduced unintentionally, with many arriving on plants imported for landscaping. They tend to be small, similar in color to the plant and have the ability to hide in wood, roots or buds. Widespread container use and the fact that inspectors only examine about two percent of all arriving cargo, makes detection even tougher.

Because of these challenges, the US is going to great lengths to improve monitoring so it can respond to infestations quickly. Unfortunately, it doesn�t always work.

Take the hemlock woolly adelgid, which was first reported in British Columbia in 1924 and not seen again until 1950 when it was found in Virginia. No one suspected its potential for destruction, so nothing was done to contain it�and the woolly adelgid is now the single greatest threat to hemlock in the eastern US.

It�s maddening to see forests lost to insects and disease, just like it�s maddening to see them lost to fire. The most sensible approach is to improve monitoring and early response and to manage our forests in a way that helps them resist infestation.