John A. Wiens (PRBO Conservation Science)
San Francisco Bay and its surroundings have always been in a state of change, but the rate and magnitude of changes have accelerated dramatically ever since gold mining in the mid-1800s deluged the Bay with sediments and contaminants. More recently, burgeoning urban development and the alteration of freshwater flows into the Bay – resulting from massive re-engineering of water distribution in the Sacramento-San Joaquin Delta – have increased pressures on natural ecosystems. And while the future is always uncertain, there is little question that sea level rise and storm surges will fundamentally alter both urban and natural areas around the periphery of the Bay.
In order to manage and conserve ecological systems in the context of past changes, and adaptively respond to ongoing and future changes, it is essential to understand where we are now. The State of the Birds: San Francisco Bay 2011 summarizes what we currently know about bird populations and their recent trends in the Bay Area.
San Francisco Bay is an area of hemispheric importance to migratory waterbirds. It harbors populations of species that have undergone evolutionary diversification in different parts of the Bay. Several of these populations are officially recognized as Threatened or Endangered, and others are of special conservation concern. In a broader sense, birds are indicators of the overall condition of habitats and ecosystems in the Bay – the proverbial "canaries in the coal mine." Tidal-marsh species can tell us not only about the condition of the marshes, but about the capacity of those marshes to provide huge benefits to people – ecosystem services – through flood protection and enhancement of water quality. And, at the end of the day, birds are an essential part of what makes San Francisco Bay a truly special place.
The State of the Birds report details the many factors that threaten bird populations in the Bay Area. Some of these – predators ranging from house cats to peregrine falcons; competition with invasive species such as barred owls; or continuing loss of habitat in the face of development – are clear and present dangers. Others, such as the drowning of marsh habitats due to sea level rise, are lurking in the future.
Yet others may be unintended consequences of our own conservation work. A major effort is now underway to restore a network of artificial ponds once used for salt production to tidal marshes. This restoration will create new habitat for marsh-dwelling species such as Common Yellowthroats or Clapper Rails. At the same time, however, it will reduce the amount of shallow open-water ponds that some nesting birds, ducks, and wintering shorebirds currently use.
How these ripple effects play out may depend on whether other processes (such as sea level rise) create suitable habitat elsewhere. This largest restoration project on the West Coast is something to be proud of, especially as it moves forward with ongoing monitoring helping to quantify the impact to birds, making course corrections as needed to ensure the most benefit for birds in the San Francisco Bay estuary.
Dealing with the conservation challenges is not simple. But neither is it impossible. At a time when news reports seem to contain only discouraging messages about the state of nature, The State of the Birds indicates that populations of many species in the Bay Area are stable or increasing, and it highlights several examples of conservation success. These, together with the many specific recommendations for actions by managers, scientists, or the public that may help to counter downward trends for other species, give hope.
Above all, the report emphasizes the importance of monitoring. We know what we know now because populations of several species in the Bay Area have been monitored for more than a decade. Continued monitoring will enable us to spot troubling trends and take actions to address the root causes before they become emergency-room cases.