Threats

Wetland Loss

After more than 150 years of human development and pollution around the edges of the bay, more than 500,000 acres of wetlands including tidal marshes, salt ponds, mudflats, stream corridors, and seasonal wetlands have disappeared. Wetlands play a vital role in our ecosystem. They provide nesting, spawning and rearing space for fish, birds and mammals and are a rich source of nutrients and food. Wetlands serve as a natural filtration system for keeping our waters clean; control flooding; recharge groundwater; and prevent shoreline erosion. Efforts are currently underway to re-establish the lost wetlands of the Bay, but at the current pace, it will be more than 100 years before they are fully restored.

Fish population decline

As the Estuary has been dammed, diverted, polluted and overfished, these stresses have combined to significantly reduce fish populations in the Bay-Delta. In particular, the populations of several sensitive species - Longfin smelt, Delta smelt, Pacific herring, and striped bass - are critically diminished, and the population of Chinook salmon remains very low.

Food Web in Peril

In addition to the reduction of specific fish populations, other species in the Bay-Delta have been sharply reduced by environmental stresses. Plankton, the basis of the entire marine food chain, are at critically low levels, particularly in the Delta. Invertebrates like crabs, shrimp, clams and oysters are at much lower levels than they were 50 years ago. Additionally, exotic species such as the Asian clam and the Northern pike are rapidly invading the Bay-Delta, profoundly altering our food web and ecosystem.

Water Pollution

Efforts to implement the Clean Water Act in recent decades have reduced the amount of pollutants discharged into the Bay-Delta. However, pollution sources such as stormwater runoff and agricultural pesticide use continue to contaminate the Bay-Delta. And some of the most toxic pollutants - mercury, PCBs and DDT - persist throughout the Estuary and are found in fish, birds, and marine mammals.

Reduced Freshwater Inflow

The Estuary needs flows of freshwater to support the habitat of estuarine species. Currently, freshwater is diverted from the Delta to support agriculture and cities throughout the state, reducing the amount flowing downstream. California is struggling with how best to balance the demands of agriculture and urban centers with the need to protect and maintain the waters of the Delta.

Human Overuse and Development

For generations, humans have enjoyed the resources of the Bay-Delta with no vision for long-term conservation of those resources. Only in the last twenty-five years have efforts emerged to care for and protect the Estuary, and we have much more work left to complete before the future of the Bay-Delta is assured. We must increase the efficiency of our water use, continue to closely monitor the health of the Bay-Delta, and implement coordinated strategies to remove toxics, increase freshwater, and improve habitats in the San Francisco Bay.

Climate Change

The relative annual sea rise in the last two decades has been nearly double the historic rate recorded since 1854. Global warming could lead to an increase in sea level of 2-3 feet in the next 100 years, threatening shoreline communities and property, low-lying farms and wetlands.

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