Higher albedo of snow-covered ground a factor in climate mitigation calculations
By Bob Berwyn
FRISCO — Snow farming is nothing new for ski area operators, who have long been cultivating the white stuff to help keep their slopes covered. Now, a recent study by researchers at Darthmouth College suggests that snow farming could also make sense on a larger scale, in the context of climate-change mitigation.
In a novel look at forests and snow, their report says that replacing forests with snow-covered meadows may provide greater climatic and economic benefits than if slow-growing trees are left standing in snowy high latitudes. In those areas, persistent snow cover reflects heat back into space, partially offsetting the effect of heat-trapping greenhouse gases.
The study is the first to put a dollar value on snow’s ability to reflect the sun’s energy. For now, sthe cientific literature includes some coarse geographic boundary lines where the concept could make sense, Dartmouth College research associate Dave Lutz said via email.
“We are about to run a series of model runs that will help elucidate these borders in a much more fine-scale way (for New Hampshire),” Lutz said. “It is important to remember, too, that there are other factors that are important when thinking about cutting forests down – biodiversity, providing hydrological regulation services, cultural and aesthetic values,” Lutz said.
Essentially, the study suggests more frequent logging or deforestation may better serve our planet and pocketbooks in high latitude areas where snowfall is common and timber productivity is low.
Such a scenario could involve a cap-and-trade style program or ecosystem services market, in which land owners are paid to maintain snow cover rather than produce timber or conserve forests.
Previous studies have put a price on many ecosystem services — or services that nature provides to humans that have both economic and biological value, such as drinking water and crop pollination — but the Dartmouth study is the first to do so for albedo, or the surface reflection of incoming solar energy.
The findings will be presented Dec. 12th at the American Geophysical Union’s annual fall meeting in San Francisco in the Global Environmental Change High Profile Topics session. A PDF of the study is attached.
Climate change mitigation projects, such as the Kyoto Protocol, encourage reforestation because growing forests take up carbon dioxide. But some studies suggest the cooling aspect of surface albedo could counterbalance the benefits of forest growth.
The Dartmouth researchers placed an economic value on timber through wood prices, as well as on albedo and carbon by using a sophisticated model of the climate and economy called an integrated-assessment model. They then examined the potential impact of these values on hardwood and softwood forest rotations in the White Mountain National Forest in New Hampshire. A rotation period begins when new trees are planted and ends when most of the trees are harvested.
Their results suggest that including the value of albedo can shorten optimal forest rotation periods significantly compared to scenarios where only timber and carbon are considered. For instance, in spruce and fir stands, very short rotation periods of 25 years become economically optimal when albedo is considered. The researchers attributed this to the low timber productivity and substantial snowfall in the White Mountain National Forest.