The ground around San Francisco Bay is sinking to meet the rising sea, another reason for Bay Area residents to worry about the impact of climate change on their region.

A new report suggests that sinking land, known as land subsidence, will increase the potential reach and damage of flooding in the Bay Area, submerging a larger portion of the region by the year 2100 than previously estimated.

Treasure Island Lake Merritt San Francisco Oakland Calif. San Francisco Bay Oakland International Airport Areas in red would be submerged by sea level rise and land sinking Hayward San Francisco International Airport Union City Foster City San Mateo Includes areas of marshland Pacific Ocean Palo Alto Areas in orange would be submerged by sea level rise alone Santa Clara Treasure Island Oakland San Francisco Oakland International Airport San Francisco International Airport Hayward Union City Foster City San Mateo Palo Alto Santa Clara Would be submerged by sea level rise and land sinking Would be submerged by sea level rise alone Treasure Island Lake Merritt San Francisco Oakland Calif. Oakland International Airport San Francisco Bay Pacific Ocean Hayward Areas in red would be submerged by sea level rise and land sinking San Francisco International Airport Union City Foster City San Mateo Includes areas of marshland Palo Alto Areas in orange would be submerged by sea level rise alone Santa Clara By The New York Times | Source: Manoochehr Shirzaei

Subsidence can be caused by groundwater pumping, which can act to “deflate” the ground above it or the gradual compacting of landfill — when lands are filled in an effort to create solid ground to build upon.

The authors of the report — Manoochehr Shirzaei, a professor at Arizona State University and Roland Bürgmann, a professor at University of California, Berkeley — have combined land elevation data with rising sea level projections. And they are now challenging the current flood threat projections as too conservative.

The authors hope that their new findings will help cities and agencies produce more accurate hazard maps, updating the extent of affected areas.

Under the new projections, San Francisco International Airport could see half of its runways submerged by the year 2100. Original estimates that did not include land subsidence were much lower. Other areas around the Bay that have been built on engineered landfill, like parts of Foster City and Treasure Island, are particularly vulnerable to the dual impact of subsidence and sea level rise.

Extent of effects of sea level rise Extent when combined with sinking land San Francisco Bay San Francisco Bay San Bruno San Bruno San Francisco International Airport Millbrae Millbrae Burlingame Burlingame Extent of effects of sea level rise Extent when combined with sinking land San Francisco Bay San Francisco Bay San Bruno San Bruno San Francisco International Airport Millbrae Millbrae Burlingame Burlingame Extent of effects of sea level rise San Francisco Bay San Bruno San Francisco International Airport Millbrae Burlingame Extent when combined with sinking land San Francisco Bay San Bruno San Francisco International Airport Millbrae Burlingame By The New York Times | Source: Manoochehr Shirzaei

The combination of rising sea levels and sinking ground increases estimates of the total amount of endangered areas to a range of 48 to 166 square miles. The rate of sink plays a role in the severity of the estimate: While most areas around the Bay are sinking at less than two millimeters per year, some have been found to be sinking at a rate as high as 10 millimeters per year.

Dr. Shirzaei said that the new estimates take into account a range of outcomes, from a “best case scenario” of sea level rise — assuming countries follow the 2015 Paris agreement for emissions reduction — to more extreme cases, where the sea level rises faster because of an accelerated melting of Antarctic ice. At the more severe end of the spectrum, the level of flooding would far exceed the effects of sinking land.

Scientists have long tracked the effects of global warming on the planet’s water levels. A recent study of 25 years of satellite data pointed to climate change as a cause for the acceleration of rising sea levels, making previous estimates unreliable.