Skip directly to: Main page content

Climate Change

Science Supporting Policy in California and Beyond

Photo: Mark Schwartz of UC Davis

Mark Schwartz develops methods to predict extinctions as a result of climate change  » READ MORE

Ecological Forecasting

What is the basis for predictions of extinction due to climate change, and how can the diversity of earth be managed to avoid the catastrophic levels of extinction that have been forecasted?

Mark Schwartz, environmental science and policy, believes that climate change is likely to be a major driver of extinction. Predictions of climate change driven extinctions are severe and range from 15-30 percent of all species on earth. Scientists estimate that only abut 20 percent of all species on earth have been described, therefore the majority of future extinctions are likely to be species that are not yet known to science. These predictions are derived from estimates of the relationship between known species and range size. Assumptions built into these predictions are that species distributions are constrained by climate, and that species are limited in terms of their ability to move to more favorable habitats. These assumptions have strong observational support but they carry large uncertainty. Species predicted as the most vulnerable to climate change are those with very small geographic ranges. These species, however, are also the ones where climate may play a minor role in determining range boundaries. Emerging studies suggest that these range-limited species may be more robust to changing climate than previously thought. One management technique that could be used to help alleviate climate-driven extinction is to help plants and animals disperse into new habitats that are climatically suited -- called assisted migration. Although some species can be rescued this way, previous experience suggests that some unintended negative consequences should be expected. As a result, ecologists should engage in this solution reluctantly and with ample evidence of an imminent extinction risk.

How will California's native fish population respond to climate changes?

Peter Moyle; wildlife, fish and conservation biology; researches the ecology and conservation of California fishes, in relation to change of all types—including climate change. His research program involves developing strategies for floodplain fish conservation in the Central Valley. He also developed methods to determine the health of mountain meadows by inventorying communities of plants, fish, aquatic invertebrates, and amphibians. He is reviewing the status of all distinctive types of salmonid fishes in California, and he conducted long-term studies of fish in Sierra Nevada streams, Putah Creek, and in Suisun Marsh. He served on the Ecosystem Restoration Program Science Board of the California Bay-Delta Authority and National Research Council Panel on the Klamath River. Moyle coauthored “Envisioning Futures for the Sacramento-San Joaquin Delta – 2007,” a report that presents the solutions to maintaining Delta as a productive, fish-friendly ecosystem.

Has climate change been observed at Lake Tahoe and how does it affect the clarity of the lake and the local ecology?

Geoff Schladow, director, Tahoe Environmental Research Center, and his collaborators have determined that climate change is as important at Lake Tahoe as it is elsewhere in the Sierra Nevada. The hundred year data record from Tahoe City, California shows that minimum air temperatures have risen over four degrees Celsius and are now above the freezing point of water, the result of which is less snow, more rain, increased runoff and more erosion. There has also been a measured increase in the temperature of the lake over the last 40 years. The warming of the lake is double the rate of warming of the surface of the world's oceans. Lake Tahoe's clarity is largely affected by very fine particles that come from the air or enter the lake with the runoff from streams and urban areas. As precipitation patterns continue to change in response to climate change -- for example more rain and less snow -- and as the runoff changes with earlier snowmelt, the quantity and size of fine particles will change. Current research uses models to predict the magnitude of changes in clarity due to climate change. Rises in lake temperature have profound impacts on the lake ecology. Current research is looking at the impacts of climate change on algal species composition, invasive fish and aquatic weed populations, and the food web.