The following case study is part of a forthcoming NPS handbook on climate change entitled “Climate Change and Cultural Resources: Impact Assessments and Case Studies.” The original author is Caitlin Smith.
Amidst the urban environment of San Francisco, Golden Gate National Recreation Area embodies a rich and diverse cultural landscape chronicling over 200 years of American history. Golden Gate’s 739 historic structures (including 5 national historic landmarks), 9 documented cultural landscapes, and 61 archeological sites reveal material histories of Native Miwok and Ohlone culture, the Spanish and Mexican periods, Pacific maritime history, the California Gold Rush, American military coastal fortifications, and the growth of urban San Francisco (NPS.gov 2011, History and Culture). These resources, together with many significant natural features of the San Francisco Bay Area, including sandy beaches, foggy skies and coastal redwoods, comprise the area’s vast cultural landscape.
Changes to the Bay Area’s climate are expected to impact Golden Gate’s cultural resources in a number of ways. Scientists anticipate an increase in precipitation and storm intensity along the Pacific Coast, which would likely increase wave height, flooding and erosion threats to many historic structures and resources (NPCA 2011). In addition, sea level could rise more than three feet by the end of the century, further threatening historic structures as well as archeological and cultural sites throughout Golden Gate. Warmer drier summers and altered wind patterns could change the presence of fog in the Bay Area, having serious consequences for the well being and survival of coastal Redwood forests that characterize the north Pacific coast (NPS.gov 2011, Nature and Science).
A trend of increasing storminess along the California coast poses the most immediate threat to Golden Gate’s cultural resources. All 59 miles of beaches in Golden Gate National Recreation Area, which are some of the most heavily used areas in the entire National Park System- are considered very vulnerable to climate change impacts due to their coastal slope, wave heights, and range of local tides (Saunders and Easley 2006). There has been a general increase in the frequency and size of winter storm waves that impact the Bay Area over the past 6 years (Barnard 2010). Increasing wave size, precipitation, and flooding is expected to dramatically increase coastal erosion and sediment transport, threatening structures along a large percentage of the coast. A study released by the Heinz Center estimates that 25% of houses within 500 feet of the U.S. shoreline could be claimed by coastal erosion in the next 60 years (Heinz 2000). At Golden Gate, several historic structures may be included in that number. Historic Fort Mason and portions of the grounds of the Presidio of San Francisco (a National Historic Landmark)–the oldest continuously used military post in the country–are low enough to be consumed by rising waters and increasing coastal erosion (Saunders and Easley 2006). On Alcatraz Island, the historic fortress/prison structure, military installations, and archeological excavations are all vulnerable to storm erosion damage and inundation resulting from climate change.
Imbued with regional identity, California’s towering redwood forests of the Bay Area are threatened by climate change. Fog and redwoods have long been associated with one another. Redwoods only live in the foggy zone of northern California and southern Oregon (Johnstone 2010). Fog that comes off the Pacific Ocean provides necessary moisture to redwoods through their canopy leaves, preventing drought stress in the long dry California summers (Limm 2009). Research at the University of California at Berkeley recently found that fog frequency has decreased by 33% (or three fewer hours of fog per day) along the California coast since the early 20th century (NPCA 2011). Under less foggy conditions, the trees lose water at a considerable rate (Johnstone 2010), possibly forcing them out of their traditional range in Muir Woods National Monument within Golden Gate National Recreation Area (Limm 2009).
Climate change may fundamentally alter the way people interact with Golden Gate National Recreation Area. The changing appearance and composition of the cultural landscape that makes up Golden Gate poses certain challenges to interpreting and maintaining the area’s historical significan ce and integrity. However, like so many places in the National Park System, climate change will become part of the legacy of Golden Gate National Recreational Area, and must be incorporated into and managed as part of the great story of America’s National Parks.
1. Barnard, Patrick. United States Geological Survey (USGS) coastal and marine geology program, NPS Golden Gate Climate Update podcast, July 2010.
2. The H. John Heinz III Center for Science, Economics, and the Environment, “Evaluation of Erosion Hazards Summary” April 2000, p. 1-22.
3. Johnstone, James. University of Washington’s Joint Institute for the Study of Atmosphere and Ocean, NPS Golden Gate Climate Update podcast, July 2010.
4. Limm, Emily. University of California Santa Cruz, NPS Golden Gate Climate Update podcast, November 2009.
5. National Parks Conservation Association State of the Parks, Muir Woods National Monument: a resource assessment, January 2011, p. 1-36.
6. NPS.gov, Golden Gate National Recreation Area, History and Culture, last modified July 5, 2011, http://www.nps.gov/goga/historyculture/index.htm.
7. NPS.gov, Golden Gate National Recreation Area, Nature and Science/Environmental Factors/Climate Change/Threats to Golden Gate, last modified July 5, 2011, http://www.nps.gov/goga/historyculture/index.htm.
8. Saunders, Stephen and Tom Easley, Losing Ground: Western National Parks Threatened by Climate Disruption, The Rocky Mountain Climate Organization, Natural Resource Defense Council, July 2006, p.14.