Arizona wildfires leave bitter aftermath for water, climate

Shaun McKinnon in the Arizona Republic: The physical scars burned into Arizona's forests this summer are the most visible proof of wildfires' fury, but the aftermath will spread far beyond the charred landscape. The loss of so many trees and other vegetation will affect air and water quality for years to come, some Arizona scientists say, reversing the ability of forests to help slow climate change and protect desert water supplies.

So far, more than 932,000 acres have burned statewide this year, a total closing in on the 975,000 acres in 2005, the worst year on record. Not all the acres were in forests and not all were severely burned, but the toll on the state's wildlands is significant.

"What's really key here is the forest's recovery," said Tom Kolb, a tree physiologist at Northern Arizona University's School of Forestry. His research includes the site of a fire near Flagstaff where a forest that once absorbed carbon dioxide now emits it, the result of decomposing dead trees on the ground and newly grown grasses and shrubs, which absorb far less carbon.

..."We are concerned that we are witnessing the conversion of forests that take in carbon and store it to vegetation types that have little ability to do that," Kolb said. "That is a situation where these fires will contribute to global warming. We've reduced the capacity of the land to store carbon dioxide."

On severely burned forest floors, meanwhile, the trees and shrubs that help contain runoff from storms and melted snow are gone. The result, hydrologists say, is floods that will fill streams and creeks with sediment. Aquifers, springs and rivers will suffer losses as less water percolates into the ground....

High winds and low humidity fueled extreme fire behavior as the Wallow Fire continued to consume acres of forested land in the mountains of eastern Arizona on June 7, 2011. By the end of the day, the fire had burned 311,481 acres (487 square miles), up 77,959 acres (122 square miles) from the previous day. As the fire raged, smoke poured across the United States, clouding skies over the Midwest. NASA, June 2011