12/18/2012: Rising Seas - The Big Picture


With an eye to the past, Marc Holmes considers what sea level rise will mean to the SF Bay Area.


Marc Holmes is a wetland regulation and restoration policy expert with 25 years of experience. He served as a United States delegate to the Ramsar Convention on Wetlands of International Importance and represented the U. S. Information Agency as part of a program to discuss wetland protection in Brazil. From 2003 until 2009, he was the California State Senate appointee to the CalFed Bay-Delta Authority, the agency charged with restoring the ecological vitality of the estuary ecosystem. Marc has been with The Bay Institute for thirteen years.


The first people arrived in the San Francisco Bay area about 12,000 years ago. Their immigration was greatly aided by sea levels 300 feet lower than those today, enabling them to migrate from Asia by both boat and foot along a broad coastal plain that extended southwards down the North American continent.

Once they arrived, they had to move their homes and villages every few years because the Pacific Ocean was continuing to rise, and at a pretty good clip. In fact, it didn’t slow down until about 2,000 years ago. Archaeologists estimate that the roughly 400 prehistoric village sites found around the Bayshore today were home to between 25,000 and 40,000 California Indians when Europeans first arrived. Off-shore, there are far more submerged archaeological sites that were drowned by the rising Pacific Ocean over the course of 10,000 years.

We now find ourselves in the same position as the prehistoric inhabitants of the Bay Area. Sea level is on the rise again, and at a far greater rate than before. Now, however, there are six million of us living here, and our “villages” are far less portable. Houses on the edge are already tumbling into the sea or are severely damaged in the increasingly frequent “storms of the century."

 
Tens of thousands of acres of Bay wetlands were unwisely converted to salt ponds.
Here, in Redwood City.

But we do have some time to plan a retreat from the shore. We have a few decades to avoid, or prevent, the slow-motion tsunami that is already on the move. Over the next 40 to 50 years, higher sea levels on calm days won’t be a big deal. The greatest threat to Bayshore development will be from storms - storms that come with increasing frequency and cause much more damage due to higher tides.

The most effective and cheapest way to protect shoreline development from these storms is to restore more than 100,000 acres of wetlands that were unwisely destroyed during the past 160 years. These marshes actually reduce the size and velocity of storm waves. Engineers have done the math: by destroying these wetlands, we increased the damage done by storms last century.

If we are to prepare for sea-level rise in a manner that makes both ecological and economic sense, we have to re-grow the marshes, which takes time. The project is already underway, but inching forward at a lethargic pace, not because the marshes are too slow, but because elected officials don’t see it as a priority. The longer they wait, the more costly it will be to retreat when things really heat up later on. Unaffordable, actually.