One of the greatest threats from global warming to coastal national parks, such as Point Reyes, is rising sea levels. Global sea levels have risen about eighteen centimeters (seven inches) during the past century, and in 2001, the Intergovernmental Panel on Climate Change projected another 7- to 88-centimeter (3 to 35 inches) rise by 2100 with the greatest probability being a rise of 48 centimeters (19 inches). Several recent studies, however, indicate that much greater rises in sea level could be coming. One report, commissioned by the state of California, gave a range of projected sea-level rise from 10 to 78 centimeters (4 to 31 inches). Another study found that future warming could be enough to melt polar ice caps, potentially leading to a meter (three feet) of sea-level rise this century and as much as 6 meters (20 feet) over the next four or five centuries. These swelling seas will transform the Point Reyes visitors have come to treasure, both for its wildlife and for its powers to rejuvenate. 

The U.S. Geological Survey (USGS) identified Point Reyes National Seashore as particularly at risk among American shorelines, along with Golden Gate National Recreation Area. The USGS rated the vulnerability of all the beaches on the west side of Point Reyes -- where wave heights are highest and coastal slopes are low -- as high to very high. The estuaries of Abbotts Lagoon and Drakes Estero, adjacent to the coastline, are at risk as well. Seals and sea lions breed on the beaches and the pristine habitats help lure nearly 490 species of birds, giving Point Reyes the greatest avian diversity of any national park. Unfortunately, sea level rise could endanger this rich habitat.

Sea level rise will also likely flood low lying roads, such as sections of Sir Francis Drake Boulevard and Highway 1 along Tomales Bay, Sir Francis Drake Boulevard at the head of Schooner Bay, and Highway 1 and the Olema-Bolinas Road along Bolinas Lagoon. Many of these roads already flood during winter storms and the national, state, and county governments may have to expend millions of dollars to either protect or relocate these roads as sea levels rise even higher.

The San Francisco Bay Conservation and Development Commission has produced some maps showing a few areas around San Francisco Bay that would be flooded with a sea-level increase of 1 meter (3 feet).

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