For thousands of years Native Americans lived in the Bay Area harvesting animals, salt, and acorns. The changes they made to the landscape were limited. They used fire to shape oak woodlands and grasslands. cultivated plants, and collected salt in tidal marsh ponds. More recent human activity has dramatically altered the bay ecosystem to its detriment. Efforts to protect and restore the ecosystem have emerged as we have gained understanding of its immeasurable value.
The Sacramento and San Joaquin Rivers carry eroded rock and soil to the bay as sediment. During the last 200 years humans have greatly accelerated this natural process, shrinking the overall area of tidal marsh. In the late 1800's Gold mining washed over 765 million cubic meters (one billion cubic yards) of Sierra Nevada into the bay. Early State legislation encouraged the conversion of wetlands to farmlands, while cities filled marshes to expand their boundaries. By 1950, only 25 percent of historic tidal marsh remained. At the same time, inadequate sewage treatment and unregulated dumping of industrial waste polluted the water. Together these changes seriously compromised the heath of California's largest estuary.
Attitudes shifted as understanding of wetland's invaluable processes grew. Images of reeds and egrets replaced those of mud and mosquitoes, leading
to regulation of bay fill and pollution. However, other threats persist. Water diversion for agriculture and urban uses disrupt fresh water flows, altering the bay's salinity and flow patterns. Contaminants from urban and agricultural run-off are washed into the estuary during winter storms, and pollution from past unregulated dumping remains in its sediments. Non-native species of plants and animals, erosion, and rising sea level are further concerns.
These changes present a considerable challenge to the restoration of the estuary's ecological processes. Restoration is a developing science, and much is unknown about the long-term success of these efforts. Coordinated research, planning, and implementation of restoration projects are crucial to find environmental solutions that benefit the diverse community of plants, animals and people that depend on this invaluable ecosystem.