Tree rings tell storyof SF Bay's salinity

The University of Arkansas researchers and scientists at the Scripps Institution of Oceanography in La Jolla say the trees' rings are leading them to that conclusion.

They used the blue oaks' ring record and reports of salinity in the San Francisco Bay Estuary dating back to 1922 to reconstruct the bay's historic salinity levels.

Elevated levels of salt content could damage the ecosystem of the estuary, which serves as a breeding ground for marine life in the North Pacific Ocean, scientists say.

Until researchers used the tree rings to measure salinity levels, there was little evidence of the bay's historic salinity levels to compare with current levels, scientists say.

Researchers used 12 blue oak sites in the state to take soda-straw sized cores from an average of 30 trees at each site.

Wider rings indicate abundant water during the growing season. Small, narrow bands point to low precipitation or drought conditions depending on the width of the growth rings. The trees have some of the highest sensitivity to rainfall of any trees in the world, researchers say.