Scientists and policy makers have said for some time that if we are to prevent the most harmful consequences of climate change we must reduce the concentration of greenhouse gases in the atmosphere. In practice, this translates into strategies such as enhanced fuel efficiency for vehicles, innovative carbon capture devices and implementation of market-based approaches, like emissions trading.
Such approaches are referred to as climate change mitigation strategies. Although we find them to be consequential to the long-term health of San Francisco Bay, climate change mitigation generally lies outside the scope of Baykeeper’s mission given the national and international scale of the strategies involved.
It is now generally accepted that even if climate change mitigation strategies were adopted immediately and on an international scale, temperatures around the globe would continue to rise for some time – requiring us to adapt to the consequences.
In California, likely impacts include reduction of the snowpack in portions of the state’s mountain ranges; changes to the scope and size of habitat suitable for some sensitive species; and faster melting of the Sierra snowpack earlier in the year – resulting in increased flood risk in the Central Valley and reduction in available water resources throughout the state.
Coastal areas will be subject to sea level rise resulting from widespread melting of polar regions, combined with thermal expansion of our seas, which could significantly impact the most populous regions of California.
Researchers have found the Bay Area to be the region along California's coast facing the greatest impacts from climate change, in terms of ecological change, infrastructure flooding and land use modification. Given the highly probable and very tangible consequences of sea level rise in San Francisco Bay, along with interest among state agencies to develop sea level rise adaptation strategies for the region, Baykeeper has focused its efforts on addressing sea level rise as part of an approach to climate change adaptation.
Sea Level Rise in San Francisco Bay
Sea level rise is a natural process that has filled San Francisco Bay on a cyclical basis over the last several hundred thousand years. At the peak of the last Ice Age, approximately 18,000 years ago, sea levels were about 120 meters lower than they are today and the shoreline extended beyond the Farallon Islands, around 19 miles from the current coastline. In the 1990s, however, the pace of global sea level rise increased significantly, based on independent measurements taken around the world.
Conservative estimates of sea level rise within San Francisco Bay indicate an additional 150 cm increase by 2100, which far exceeds the Bay's historic increase of 2.2 cm/decade. Under the most optimistic scenarios, representing significant reductions in current greenhouse gas emissions, researchers estimate increased temperatures will raise sea levels 40 to 70 cm by the end of this century.
Given the scale of urbanization in the Bay Area and the gentle gradients extending from the Bay to cities and sensitive habitats, even moderate levels of sea level rise could have a very significant impact on urban landscapes and tidal wetlands of the San Francisco Estuary.
Assuming 140 cm of sea level rise an estimated 270,000 people in the Bay Area are at risk of flooding, along with $62 billion worth of shoreline developments and associated infrastructure. This could also risk the long-term sustainability of wetland restoration projects located in Suisun, San Pablo and South San Francisco Bays.
Sea Level Rise Adaptation Policy in the Bay Area
Among the most pressing requirements of climate adaptation is the need to address sea level rise within urban environments, such as the Bay Area. To do this, we must develop common planning tools for assessing flood risk and envisioning a built environment capable of adapting to rising seas without placing additional strain on natural resources.
Within the context of our nation’s current political environment, however, concrete sea level rise adaptation policies are not likely to arise from national or even state lawmakers. Instead, regional or local strategies will likely pave the way for broader policy goals or future rulemaking decisions.
In 2009 the San Francisco Bay Conservation and Development Commission (BCDC) originally proposed an amendment to the Bay Plan that would effectively mark the first steps towards a comprehensive sea level rise adaptation policy for San Francisco Bay. This policy has been viewed by some experts in the field of coastal engineering and climate adaptation as an early measure of the nation’s capacity to impose land use requirements and actionable strategies based on sea level rise projections and public policy recommendations.
The amendment suffered repeated delays and came to be what staff considered possibly the single most contentious issue in BCDC’s 45 year history. However, in October 2011 the policy passed unanimously by members of BCDC. Baykeeper has remained supportive of BCDC’s efforts and plan on actively engaging in the development of a regional sea level rise adaptation strategy, as required by the new Bay Plan amendment..
Read more to find out about the Bay Plan amendment and needed next steps.
San Francisco Bay Development Commission. 2009. Draft Staff Report: Living with a Rising Bay: Vulnerability and Adaptation in San Francisco Bay and on its Shoreline.
California Climate Adaptation Strategy. 2009. California Natural Resources Agency
Heberger, M., H. Cooley, P. Herrera, P. Gleick, E. Moore. 2009. The Impacts of Sea-Level Rise on the California Coast. Prepared by the Pacific Institute on behalf of the California Climate Change Center.
Knowles, N. 2010. Potential Inundation Due to Rising Sea Levels in the San Francisco Bay Region. San Francisco Estuary and Watershed Science. 8:1. Click here for accompanying Google Earth images.
U.S. Buueau of Reclamation. 2011. SECURE Water Act Section 9503(c) – Reclamation Climate Change and Water. Report to Congress.