How does climate change affect valley?

By MARTHA CONKLIN and LARA KUEPPERS

last updated: December 03, 2007 05:09:23 AM

In the face of global climate change, one important role for science is to investigate the areas in which society is vulnerable to climate warming and to help guide efforts to adapt to changes.

What resources might be threatened and how? At the University of California at Merced, we are addressing this question for several important regional resources.

A significant fraction of California's water supply comes from the Sierra Nevada snowpack. With our mild winters, temperature increases of only a few degrees will be enough to turn what are now mountain snowstorms into rainstorms. The implications for earlier runoff, more severe spring floods and drier summer soils in mountain forests are motivating a broad-based research effort to understand the mountain water cycle.

The foundation for this research is a new generation of measurements to get a quantitative understanding of snow distribution, snowmelt, soil moisture, water use by plants and processes that determine the timing and magnitude of streamflow. Strong academic- applications partnerships, some of which are in place and others still developing, are the key to making this research possible and assuring that results are useful to decision-makers in the state.

In addition to the global effects of our carbon emissions, human activities affect the climate on a regional scale. For instance, we have found that in the Central Valley, agricultural irrigation can mask the effects of climate warming.

When watered, farmland acts like a giant swamp cooler. Future land-use changes that replace fields with housing and businesses could turn down the air conditioner and make us more vulnerable to the warming climate.

Species and ecosystems in the high mountains are especially vulnerable to climate change, driven by the effects of higher temperatures on the water cycle and plant growth. How mountain plant species, such as alpine wildflowers and pine trees, respond to higher temperatures and drier summers is not well-known. It all depends on how climate warming will affect ecosystem interactions, not just plant species in isolation.

Already, animals that make their homes on mountaintops, such as the rabbitlike pika, are in danger of extinction. These habitats and species bring millions of tourists to the Sierra each year. We are striving to learn more about these sensitive ecosystems to improve their chances of weathering the changes ahead.

Research has shown that increased risk of wildfire in mountain forests is linked to climate warming. Earlier and warmer springs lead to a longer fire season and more dry vegetation that is vulnerable to frequent, large wildfires. Recent surges in wildfires can be explained in part by fire suppression and land-use changes, but climate warming has driven much of the increase.

Forests in California's Sierra Nevada are especially vulnerable because they are affected by warming and fire suppression. Mountain wildfire threatens tourism, timber and public disaster response resources. It is an area where we must adapt our systems to the reality of climate change. Research that integrates across forest health, wildlife, water and human concerns is helping to provide the knowledge base for adaptation.

Individual, day-to-day changes to reduce emissions and slow climate warming are vital. But climate warming is already under way, thanks to past choices. Research efforts such as these can help draw attention to areas where we must proactively adapt lifestyles, economies and resource management to be better stewards of our resources today and into a warmer future.

Conklin is a professor in the UC Merced School of Engineering; Keppers is a professor in the UC Merced School of Natural Sciences. Both work in UC Merced's Sierra Nevada Research Institute.

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