Systematically Thinning Forests Increases Runoff by 9%-18%
Researchers at the University of California who are trying to squeeze more moisture out of Sierra forests by thinning them are confirming that every drop counts.
That’s not news to the state’s farmers, who seem to spend as much time protecting their sources and supplies of irrigation water as they do in producing the state’s 350 commercial crops. They’ll take every bit of help they can get.
Rob York manages the university’s 4,000-acre Blodgett Forest in El Dorado County, a tiny percentage of the more than 15 million acres of forest growing in California, from 3,000- to 12,000-foot elevations. He contends that the amount of water that runs off the forests every year can be increased from 9 to 18 percent by systematic thinning of the trees.
York says about half of the state’s forest lands are privately owned, and the rest are owned and maintained by the state or federal government. Timber companies and others who own forest land are among the most cooperative when it comes to supervision of the land and trees. The federal government cooperates as well, but water yield is not high on its priority list.
He refers to the trees growing on the state’s hillsides as pumps. Not only do they pull moisture from the soil for sustenance, they prevent snow from reaching the ground when their branches entwine to create a dense canopy. Snow melting in the tree tops tends to evaporate, rather than fall to the soil to penetrate it and create runoff.
No wonder he and his staff advise planting of new trees and thinning of established growth. That way, more winter snow falls to ground level, penetrates to provide needed moisture for the forests and creates increased runoff for agriculture, fish and a greener environment for all at lower levels.
In his continuing management program, York receives the least cooperation from the trees themselves and the forest undergrowth. Their nature is to reproduce vigorously. But forest managers have found that the trees will grow in such profusion that they create an unhealthy environment for themselves. Forest undergrowth multiplies so fast, you might say “like weeds,” that it robs the trees of nourishment and impedes development of a manageable forest floor.
Farmers with orchards can easily identify with the need to manage tree growth and understand how trees left to themselves will overgrow and create a less than ideal orchard environment.
The other predominant issue in forest management is fire. Trees growing in crowded, unplanned patterns become gigantic tinder boxes. Both trees and the untamed undergrowth contribute to fire danger.
The aftermath of fires is tons of ash, which is carried by runoff into lakes, reservoirs, ponds and other storage facilities. In many cases, the only way to preserve the storage and holding capacity of these pools is by expensive dredging and the hauling away and disposal of the sediment.
Amateur forest preservationists seem to cling to the belief that a crowded forest is a healthy forest. York’s work disproves that erroneous though popular misconception which seemed to gain momentum a dozen years ago when the environmentalist community attached it to its hysterical campaign to preserve the spotted owl. The owl, by the way, is prospering well in thinned-out versions of its forest habitat.
York’s program brings him into contact with many environmentalists, with whom he works congenially. He might even be classified as an environmentalist himself. But unlike many in the environmental community, he has no hidden agenda. He dedicates himself to healthier forests that can reach their full potential.
Part of the forests’ potential is greater runoff, heavier production of water for the health of the trees themselves as well as everything and everybody at lower elevations.
The farm community’s conviction that every drop counts prompts it to encourage the forest research by saying: Keep counting every drop.