Tree-Ring Lab Director Testifies on Impacts of Climate Change on National Parks
Thomas Swetnam tells House subcommittee that more "place-based" scientists are needed in the nation's public lands to work with agency managers.

By Jeff Harrison, University Communications
April 7, 2009

A scientist at The University of Arizona told members of Congress Tuesday that climate change is creating a series of challenges for those who manage America's "crown jewels" of the nation's public lands, the national park system.

Thomas Swetnam, director of the Laboratory for Tree-Ring Research and a professor of dendrochronology at the UA, spoke Tuesday morning to members of the U.S. House Subcommittee on National Parks, Forests and Public Lands at a meeting in Twentynine Palms, Calif., next to Joshua Tree National Park.

Swetnam, a noted authority on forest ecosystems and their fire history, told congressmen that federal agencies and university scientists should expand the use of what he called "place-based" science models to understand how climate change may impact ecosystems and watersheds.  

He said the National Parks include many of the least human-altered ecosystems on the planet, and provide "a unique and valuable perspective on climate-caused changes that have occurred in the past and are occurring now."

Place-based science is still relatively rare. It involves locating scientists within national parks and related offices. Long-term, scientists working at a specific locale develop the kind of deep-rooted knowledge that allows them to become familiar with the natural rhythms and history of a region.

Swetnam said the approach lets scientists interact closely with managers on implementing research and monitoring efforts needed to manage changing landscapes. Currently, only a few dozen scientists are located in field stations in the western United States, and fewer in the east.

Swetnam acknowledged that there are uncertainties about future climate change impacts on ecosystems and watersheds. "Much of what we have learned about he effects of past and recent climate variations and change on ecosystems has come from studies conducted within the national parks and national forests. In the future, we need to continue and expand monitoring of climate and ecosystems within parks because these places offer some of the best landscapes to study climate-driven changes with the least amount of human land-use effects.

"The rationale for the parks was, and is, that these are the places we care the most about in terms of protecting and preserving these wonders, now and in the future," he said.

One example of climate change impact Swetnam told the congressional panel is a 2006 study published in the journal Science of forest fire activity on federal lands by Swetnam and two colleagues in California. 

During a 34-year stretch between 1970 and 1986 there was a seven-fold increase in the amount of acreage burned during the second half of the study over the first half.  Swetnam said that correlated with rising spring and summer temperatures in the region, with the largest fires coming on the heels of earlier spring temperatures.

"From locations of the large fires in different elevations and forest types, and patterns of spatial and temporal moisture deficits, it was apparent that warming climate was the key driver overall," he said. This was especially true in some regions like the Northern Rocky Mountains.

Swetnam told panel members that place-based science is an effective model that deserves to be replicated along with other forms of translational science.

"The bio-regional landscape approach is critical for providing managers with relevant, up-to-date scientific information and for ensuring climate change efforts are dynamic, flexible and consistent across the Department of the Interior and within other agencies," Swetnam said.