In several instances, introduced species have overwhelmed native species and dramatically altered the bay s life cycle. But there is speculation that it is because this system is so stressed that it is hard for the bay to fight off the invading species. Pollution, over-fishing, dredging and the decline of fresh water flows from the delta into the bay are all cited as stress factors that may impair the ability of native species to survive the introduction of exotics. The 1972 passage of the federal Clean Water Act, which forced local governments to stop dumping raw sewage into the bay, was the first important step toward reversing the bay s decline. Now, most of the 900 million gallons of effluent discharged annually into the bay is highly treated.
Raw sewage poses a problem only during and after heavy rains, when storm drains overflow.
And there have been other gains. Thousands of acres of wetlands have been restored, adding habitat for millions of migrating birds on this important stopover of the Pacific Flyway. Some endangered species have rebounded, most notably the brown pelican, which was virtually wiped out by pesticides in the 1960s. Flocks of the top-heavy birds are now a common sight, skimming the waters and diving for fish. Thirty years of reclamation efforts have even managed to slightly enlarge the inlet, which still is hundreds of miles smaller than it was before millions of people settled around its shores.