Sunday, November 17, 2013
History of the Wetlands
The San Francisco Bay was a valley until eight to ten thousand years ago, when the sea level rose and the land was inundated with ocean water. When the sea level finally stopped rising rapidly about 4,000 years ago, sediment began to build up and create the Bay’s tidal marshes. At their height, the Bay’s tidal wetlands covered 800 square kilometers and were home to diverse species and the Muwekma-Ohlone Native Americans, who used the Bay’s resources sustainably. Conversely, the Europeans settlers who arrived later had purely economic motives, exploiting and degrading the area. Intense environmental pressures also came with the beginning of the Gold Rush in 1848. In some areas, manmade marshes created by sediment from hydraulic mining replaced natural wetlands. Yerba Buena and Mission Bay were filled in to accommodate the thousands of spectators moving to the Bay. Shockingly, the state sold marshlands for $1 an acre during this period.
The Moffett Air Field was constructed on the South Bay Marshes in 1932. Next came the creation of Treasure Island, the Alameda Naval Air Station, Mills Field (which became the San Francisco International Airport), and the Hamilton Army Field. All of these projects either required the development or filling in of parts of the Bay. By 1950, 90% of the Bay’s wetlands had been destroyed. Despite the degraded state of the environment, there were still plans to continue to fill in parts of the Bay for different purposes. It wasn’t until the Army Corps of Engineers drew up a map that predicted that the Bay would become a small canal by 2020 if such extreme development persisted that people began to realize that protection and restoration was necessary. Catherine Kerr, Sylvia McLaughlin, and Ester Gulick created Save the Bay in 1961. The organization put forth massive organized efforts to stop developers from encroaching on even more on the Bay’s wetlands. Other large-scale restoration projects started in 1969. Efforts to return the Bay back to a healthier, more sustainable state continue today, such as the South Bay Salt Pond Restoration Project. Current Human Impacts
Bay Area wetlands offer a wide range of ecological services. They provide wildlife habitat for over 500 species of wildlife, 105 of which are threatened and 23 of which are endangered. They also help control flooding by holding and absorbing excess water, provide ground-water recharge, and can even contain pollutants in the flooded soil. Unfortunately, Bay Area wetlands are currently threatened by human activities such as pollution, climate change, freshwater diversion, invasive species, and shoreline urbanization. The severity of these impacts are related to population growth: the Bay Area population is expected to grow another 15 percent to 8.1 million by 2020.
Today, pollution in the Bay Area poses serious threats to the region’s wetlands. Manmade pollution comes from car exhaust, pet waste, trash, household toxins such as fluorescent light bulbs that contain mercury, and more. Pollution that comes from non-point sources is particularly problematic because it is difficult to control and contain its effects. Mercury and Polychlorinated Biphenyls (PCBs) that come from old mining activities adversely affect the wetlands since they contaminate water and poison sensitive species. When not disposed of correctly, these pollutants wash into storm drains and flow into the Bay. Run-off caused by improper waste treatment methods also pollutes wetlands with pesticides used in agriculture and chemicals from industrial activity.
Anthropogenic climate change also affects the wetlands by changing temperatures and water quality, which contributes to further decreases in species diversity. As the planet warms, sea levels increase (water expands when its hot, in addition to melting ice and glaciers), which puts pressure on many species. Climate change can also lead to changes in runoff patterns that bring more fresh water into the Bay during the winter but less in the spring and summer. Scientists predict that this will cause parts of the Delta to become saltier. This will pose a serious problem since many plants and animals are not adapted to saltier conditions. Humans’ demand for water is also contributing to the diversion of freshwater in the Delta. Freshwater supplies are pumped from the area to be used by 22 million Californians. Unfortunately, 95% of the Delta’s diverse freshwater plant habitat has already been lost. In addition, human-introduced nonnative species damage Bay Area wetland ecosystems. Plants such as Australian bent grass and iceplant can outcompete native vegetation and take over large areas, which leads to a decrease in species diversity.
Finally, urbanization is impacting Bay Area wetlands. Wetlands usually migrate inland when sea levels rise, but plants and animals are currently running out of available space because of Bay Area urban development. Table 10 lists the types and extents of areas that are currently not viable, viable but will cause property loss, and viable for wetland migration in the San Francisco Bay Area. Developed areas are considered to be not viable for wetland migration (this includes all areas with high to low intensity development). These areas constitute 35 square miles of land in the Bay Area. Although 53 square miles are considered viable, 35 square miles is a lot of space that is no longer available to wetlands. It is also reasonable to predict that people may not want to pay for the property damage that would come from making another 4.9 square miles available for wetland migration. Rises in sea level paired with the constraints of Bay Area urbanization put serious environmental pressure on the ecosystem, trapping existing wetlands within a smaller and smaller inhabitable range.
Future Prospects for the Wetlands
Future prospects for Bay Area wetlands are mostly unknown. In many ways, much progress has been made in protecting the area. When the San Francisco Bay estuary and associated wetlands in Marin were added to the list of international treaty of protected waterways in February 2013 they became the country’s 35th “wetland of importance.” Additionally, the San Francisco Bay Conservation and Development Commission continues to enforce the San Francisco Bay Plan, which was first created in 1968. The Commission works to protect wetlands and regulate development in the area. Hopefully this will continue to benefit Bay Area wetlands, especially if the regulations become even more stringent. Efforts made by environmental groups also appear to be paving the way for a more environmental future in the Bay Area. The South Bay Salt Pond Restoration Project’s work to restore saltwater wetland habitats will most likely encourage the reintroduction and growth of species in these wetland pond complexes.
However, U.S. Geological Survey scientists estimate that in 40 years Bay marshlands, like Marin Country's Core Madera Marsh, will actually be completely wiped out. Ecologist Karen Thorne says that her research indicates that there will be no Bay Area wetlands left by the end of the century, mostly thanks to the rising sea levels. Sea levels are projected to keep rising at faster and faster rates in the San Francisco Bay Area as a result of anthropogenically caused climate change. While existing wetlands could move upslope away from encroaching sea levels, Thorne says that “there’s nowhere for them to go” thanks to the urbanization in the area. It’s clear that much more work needs to be done on a larger scale to ensure a future for Bay Area wetlands.
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