Symposium explores agents of change in Sierra ecosystems
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Valerie Cassity
Special to the Sun
Climate change and its effects are here now and the future is uncertain was the take-home message of the Southern Sierra Science Symposium held at the Visalia Convention Center last Wednesday, Sept. 10. The symposium, hosted jointly by the U.S. Forest Service (USFS), National Park Service (NPS), and U.S. Geological Survey-Western Ecological Research Center (USGS), was organized around the broad scale environmental “agents of change” affecting the southern Sierra ecosystems.
The five areas of focus were climate change, fire, forest management, pollutants, and invasive species; each area had two separate presentations, the first of which focused on the current state of science and the second on the science guiding management response.
Keynote speaker, Dr. Anthony Westerling of the Sierra Nevada Research Institute at UC Merced, spoke about his climate change research studying the wildfire trends in the southern Sierra, which demonstrated that fires are burning longer and further than in the recent past. “There has been a five-fold increase in the average length of wildfires,” said Dr. Westerling, “Including a 300 percent increase in wildfire with the average area burned increasing 600 percent since 1972.”
However, Scott Stevens, Associate Professor of Fire Science at UC Berkeley, said that looking further into the past (before the forests were “managed” for fire), approximately the same area of forest had burned. “The 2008 fire area is similar to what burned before 1800 in California forests,” he stated.
As climate change affects fire trends, agencies are uncertain of what the best tactic to preserve the Sierras might be. One speaker called for the need to allow federal agencies to try different strategies and be allowed to make mistakes, while several presenters spoke of the need to change the policies in order to preserve the forest as old management models become outdated because of forest reactions. The USFS has used the strategy of removing large trees to reduce wildfire risk. However, Malcolm North, USFS research scientist for the agency’s Pacific Southwest Research Station, shared his views that logging large trees actually exacerbates the fire problem. North added that this tactic is counterproductive to reducing global climate change effects because one large pine tree can sequester as much carbon as 1,000 small trees. “Trying to propose large tree thinning projects for fuels reduction is not justified,” North exerted.
Another area of great concern addressed during the symposium was how climate change is affecting the Sierra snowpack and watersheds. At present, the scientists explained, glaciers are melting, summer is lasting longer, fires are burning farther and longer, and animals are moving upslope due to increased Carbon Dioxide (CO2) levels. One scientist demonstrated that there is little doubt that humans are at least partly the cause of the warming that is taking place, as ice cores show that the current CO2 concentrations are greater now than those of the last 20 million years. As a result, less snowfall and earlier snowmelt could wreak havoc on California’s largest water source. “The Sierra Nevada is the water tower for the Central Valley,” said Nathan Stevenson, a U.S. Geological Survey research ecologist based in Sequoia and Kings Canyon National Parks. “It supplies water for agriculture, cities and ecosystems in the valley.”
Stevenson addressed another troubling possibility about the future of the crown jewels of the Sierras, the giant sequoias. Stevenson stated his research has shown that if something is not done to mitigate climate change, the unique trees could become extinct in the next century. "We've got a lot of our most cherished species at stake," agreed Constance Millar, a senior research scientist with the U.S. Forest Service. "Rather than just managing forests for the plants we see growing there today, we're now having to look forward to think about what might thrive there in 100 years."
The symposium appeared to be a breakthrough, perhaps a paradigm shift, for the participating federal agencies; until very recently, many denied the very existence of global warming. Now that their own research has shown climate change is a reality and is impacting the health of the forests in their charge, steps can be taken to change their strategies with an eye to preserving the Sierras into future generations. “A year ago, our management partners, to put it bluntly, didn’t believe in climate change,” said Millar.
