They sequester carbon, serve as corridors and refuges for plants and animals adapting to climate change, and increasingly provide model programs for energy and water conservation.

Mike Cipra speaks about the effects of non-native grasses, such as the Red Brome he is holding, which increase opportunities for wildfires which in turn impact the reproductive cycle of Joshua Trees. They are America's national parks and, as a congressional subcommittee heard at a field hearing Tuesday at City Hall in Twentynine Palms, they could be one of the country's first lines of defense against climate change.

"We have in the National Park Service created a strategic framework," said Jonathan B. Jarvis, the agency's regional director for the Pacific West. "We are looking at how our operations may be changed so we can reduce our own carbon footprint."

Jarvis was one of eight experts who spoke at the hearing, which brought two members of the House Subcommittee on National Parks, Forests and Public Lands to Twentynine Palms to hear about the impact of climate change on parks such as Joshua Tree.

"We're in the process of formulating legislation to deal with public land and adaptation strategies," said U.S. Rep. Raúl M. Grijalva, D-Ariz., subcommittee chairman.

Grijalva and California Rep. Grace F. Napolitano, D-Santa Fe Springs, focused on how the new law - to be unveiled at a future hearing - might balance new government regulations with incentives to foster public-private cooperation and provide increased funding for park programs.

Highlights from the hearing:

Rebecca Shaw, director of conservation science, The Nature Conservancy of California: "We in California in this century (may see) an average statewide 6.8- to 10.4-degree Fahrenheit increase. San Francisco could have the climate of Los Angeles. Climate change will result in increased rates of plant mortality, including Joshua trees."

Michael Cipra, program manager, National Parks Conservation Association: "What does it mean to have Joshua Tree National Park without Joshua trees? On an economic level, fewer recreational visits; on a spiritual level, it means our grandchildren will see a diminished world."

John Harja, Western Governors' Wildlife Council: "Crucial habitat is defined differently in different states. Neither is wrong; they're established for different purposes. We're looking at primarily a decision-support system, gathering information and making it available to decision-makers."

John Coleman, senior meteorologist of KUSI, San Diego: "The science behind the current global warming, manmade climate commotion has failed to verify. My advice to the National Park Service and the subcommittee is: Do nothing to mitigate manmade global warming because there is none."

Robert B. Keiter, director, Wallace Stegner Center for Land, Resources and the Environment, University of Utah: "Our national park system should play roles - as baseline study areas, as biodiversity refuges and as carbon storage sites. Climate change will also impact surrounding communities that rely on national parks for economic welfare."

Jarvis: "I think there is a role for the National Park Service in carbon trading. In most of the large (parks), we are in active restoration. Those trees will sequester carbon. Understanding how we could market that in a carbon market would be important."