Thinning efforts are off to a great start but must accelerate, says Timothy Quinn, head of the Association of California Water Agencies. Five times as much forest should be thinned every year, estimates Roger Bales, a hydrologist at the University of California, Merced. To find out how much extra water a thinned watershed produces, the university has placed sensors in thinned and control plots in the Stanislaus-Tuolumne Experimental Forest north of Yosemite National Park. Depending on landscape and precipitation, thinned areas shed 10-40% more water into streams, Mr Bales estimates.
More accurate numbers will be available next year. The hope, says Eric Knapp, a Forest Service ecologist in Redding, is that a new thinning technique will prove to produce even more water when flow volumes from next spring’s snowmelt are known. Some plots are not thinned evenly, but rather by clear-cutting gaps with a diameter one or two times the height of surrounding trees. The idea is to clear an area big enough for a good snowpack to form, but small enough for shade to reduce evaporation and extend the melting season.
California’s governor recently signed a bill that facilitates thinning watersheds. But some environmentalists resist “cutting any tree for any reason”, as the Forest Service’s Mr Murphy puts it. And some think thinning doesn’t produce meaningfully more run-off. That’s the opinion of Chris Frissell of Frissell & Raven Hydrobiological and Landscape Sciences, a consultancy in Polson, Montana. Thinning has become popular in the state, but, he says, it disturbs soil, generating silt that harms aquatic life.
Clearing trees with fire is cheap if all goes to plan but only makes sense in certain areas. Thinning with big chainsaws on wheels can cost up to $650,000 per square mile. This could be recouped with timber revenue if big trees are felled. But the chainsaws are usually only let loose on smaller trees, so taxpayers must cough up.
One solution would be to get water utilities or hydropower producers to fund the thinning. AMP Insights, a consultancy which has estimated the value of water flowing out of the Sierra Nevada, reckons the extra flow would defray the cost of removing trees by 20% and, in wet years, by 60% or more.
Here we have one scientist (Bales) with monitors in plots saying that thinned areas get more water into streams, but (Frissell) possibly at the expense of aquatic life. We’ll explore that in greater depth in the future.
As Brian Hawthorne said earlier, thinning for fuel treatment is not the only reason to thin. Brian also mentioned restoration. Bales and others are thinking about dealing with climate change and water resources, another purpose, involving more disciplines. The scientists in the article come from a variety of disciplines.
Here’s Eric Knapp, forest ecologist.
Tim Murphy is a hydrologist/soil scientist (according to LinkedIn)
Chris Frissell seems to also be a scientist at U of Montana in addition to the consultancy the article mentions. Here’s his information. He is an aquatic ecologist.
Roger Bales works on water and climate engineering and is a professor at U of Calif Merced. Here’s his info.