Fewer big trees found in today's forests

A study conducted by scientists from UC Berkeley, UC Davis, UC Cooperative Extension and the U.S. Geological Survey found that since 1930, the density of large trees in California has decreased, reported John Fowler of KTVU News Channel 2.

The story said scientists compared exquisitely detailed tree data collected in the 1920s and 1930s with tree surveys made between 2001 and 2010. They identified significant and rapid changes in basic forest structure. As large tree density fell across the state, and the density of small trees increased.

"The thing that I think is particularly worrisome is how widespread this is," said Maggi Kelley, UC Cooperative Extension specialist in the Department of  Environmental Science, Policy and Management at UC Berkeley. "These changes will have an impact on how animals use the forest, how fire moves through the forest and the way we view the forest."

"Our grandkids will definitely see a difference," she said.

The Los Angeles Times also covered the new research, which will be published in the Proceedings of the National Academy of Sciences.

LA Times reporter Taylor Goldenstein spoke to study co-author Mark Schwartz, a professor of environmental science and policy at UC Davis and director of the John Muir Institute of the Environment. Schwartz said a denser forest allows fire to travel faster, causing more devastation. After a fire, new, smaller trees grow that are more likely to catch fire, and the cycle continues.

“These are historically fire-maintained ecosystems,” Schwartz said. “The firemen are faced with this notion of when a fire is reported and started, do they go out and bring out helicopters, trucks and people and put the fire out or do they let it burn?”

Just how much the change in forest structure is due to fire suppression and how much results from climate change is hard to tell because the two are interrelated, Schwartz said.

National Geographic magazine invoked Peter, Paul and Mary's mournful ballad in its headline, "Where have all the big trees gone? They've gone to logging and housing - but especially to climate change."

Reporter Warren Cornwall wrote that no area was immune to the forests' decline, from the foggy northern coast to the Sierra Nevada mountains to the San Gabriels above Los Angeles.

The loss of big trees was greatest in areas where trees had suffered the greatest water deficit. Large trees in general appear to be more vulnerable to a water shortfall. Though the 2011-14 drought might have an impact on  forest change, it was not reflected in this study because the data was collected before the drought began.

Read more