BERKELEY — California's coastal fog has decreased significantly over the past 100 years, potentially endangering coast redwood trees dependent on cool, humid summers, according to a new study by University of California, Berkeley, scientists.

It is unclear whether this is part of a natural cycle of the result of human activity, but the change could affect not only the redwoods, but the entire redwood ecosystem, the scientists say.

"Since 1901, the average number of hours of fog along the coast in summer has dropped from 56 percent to 42 percent, which is a loss of about three hours per day," said study leader James A. Johnstone, who recently received his Ph.D. from UC Berkeley's Department of Geography before becoming a postdoctoral scholar in the campus's Department of Environmental Science, Policy and Management (ESPM). "A cool coast and warm interior is one of the defining characteristics of California's coastal climate, but the temperature difference between the coast and interior has declined substantially in the last century, in step with the decline in summer fog."

To view the full release with photos, please visit the UC Berkeley NewsCenter.