ТОП просматриваемых книг сайта:
Mountains and Marshes. David Rains Wallace
Читать онлайн.Название Mountains and Marshes
Год выпуска 0
isbn 9781619026735
Автор произведения David Rains Wallace
Жанр Биология
Издательство Ingram
Likening the Golden Gate to a gray whale’s spout may seem farfetched, but many other analogies between the Bay and a living organism are possible. Like a gray whale, the Bay has a life span, an anatomy, and a physiology. It’s just that they are so extended in time and space that we have trouble perceiving them.
THE AGING, RENEWING BAY
San Francisco Bay has existed for at least ten thousand years, since melting ice sheets flooded its basin by raising ocean levels. Because the basin has existed much longer, as sideways movements of the Pacific and North American tectonic plates cracked and tilted California into mountains and valleys, the Bay has had ancestors at various times during the past few million years. A new bay would form when ocean levels were high during interglacial periods, then gradually silt in and revert to land when ocean waters receded.
The rise of California’s mountains did more than form the Bay’s basin. The barrier of the Coast Range forced most of the state’s main rivers to drain into the Pacific through the single outlet of the Golden Gate. Thus the Bay became not only an inland arm of the Pacific but a maritime extension of the Sacramento and San Joaquin river systems—a great estuary where most of the runoff from the Sierra Nevada and southern Cascades meets the ocean. Someday, the rivers will end this Bay’s natural life span by filling it with silt and sand eroded from the mountains. It may already be half full of sediments. They lie three hundred feet deep in places, and average water depth is only twenty feet.
Ocean and rivers shape the Bay’s anatomy. Sea level determines its extent, while rivers deposit marshy flats of silt and sand that divide open water from land. Tidal flows carve sloughs that carry water into brackish and salt marshes, while rivers and creeks cut deltaic channels and backwaters lined with freshwater marshes and riparian woodlands. Tides and streams together cut deep underwater channels that circulate throughout the Bay and converge eventually on the Gate.
Ocean and rivers regulate the Bay’s physiology. Tides that move water in and out of marshes and mudflats twice a day bring food and oxygen to organisms and carry off waste. Rivers transport vast amounts of mineral and organic nutrients into the Bay to be cycled through wetlands, mudflats, and open waters. Storms can increase rivers’ winter and spring flows sixfold. The Bay could no more stay alive without these circulating fluids than a gray whale could live without its blood. Fresh nutrients and water must continually replenish the Bay or it will be starved and poisoned. When upriver water users say that freshwater allowed to run through the Bay to the ocean is wasted, it makes as much biological sense as saying that a whale’s blood is wasted in the whale.
Estuarine wetlands such as the Bay’s are earth’s most productive habitats, fabricating four times as much green plant matter from the raw materials of sunlight, water, and silt as agribusiness cornfields. Warm waters swarming with bacterial action quickly transfer nutrients from silt to photosynthetic cells, and burgeoning algae and marsh plants form primary links in thousands of food chains. Reduced by bacteria to protein-rich detritus, they nourish vast swarms of tiny animals that drift in and out of marshes with the tide, including the young of many larger species—crabs, shrimps, fish, worms, oysters, and clams. The small drifters feed masses of other slightly larger predators that inhabit the Bay or pass through it at some stage in their lives, as with salmon and striped bass. From there, food chains ramify in myriad directions that lead eventually to egrets, cormorants, pelicans, grebes, and diving ducks; to six Bay shark species, one of which may grow to over fifteen feet in length; to hundreds of other fish species; to harbor seals, sea lions, and gray whales.
The Bay is like an enormous turbine, spinning and generating energy as organisms feed, are fed upon, and pass their nutrients along. Far from dissipating this energy, the Bay recycles it with endless ingenuity. A carbon atom carried into the delta by the Sacramento or San Joaquin might make hundreds of passages through the turbine before escaping through the Gate. At first, the atom would ride above the tides flowing in through Carquinez Strait, since freshwater is lighter than salt. It might get pushed up a slough that feeds a delta marsh, enter the roots of a tule sedge, become part of a leaf’s photosynthetic factory, then drift downstream to San Pablo Bay as detritus. There, a bay shrimp might ingest it or the tide might push it up another slough, into a salt marsh, where it would undergo the process of incorporation and decay in a pickleweed. Mixed with the Bay’s saltier waters, it then might sink to the bottom to be consumed by a worm, then by a sand dab. It might stay on the sand through generations of bottom organisms and their predators before tidal flows move it again, and when they do, they might push it back up Suisun Bay instead of pulling it down the final rocky chute of the Golden Gate. Or it might stay in the Bay sediments, an organic speck in the silica matrix of future sandstone.
Understanding the Bay system’s intricacies might require a brain as big as the Bay. But there is a more intuitive way of perceiving its vitality. Like a gray whale, the Bay is beautiful, and while this quality can’t be experienced whole, except perhaps from an orbiting satellite, it can be in hundreds of parts: on a fall afternoon at China Camp State Park, when wooded islands float in a haze above salt marshes and thousands of blackbirds flock on the horizon . . . on a winter evening at San Pablo Bay National Wildlife Refuge, when hundreds of shorebirds rest on mudflats the color of the setting sun . . . on a spring morning at San Francisco Bay National Wildlife Refuge, when orange parasitic plants called dodder growing on pickleweed glow like fire in the green matrix.
The Bay is beautiful—that is, where it is reasonably healthy, which raises another characteristic of living organisms. They can die from injury or disease as well as old age. San Francisco Bay has suffered more than its share of injury in the past two centuries, as silt from Mother Lode mining has smothered its bottom and landfill for urban growth has obliterated more than a third of its original acreage. Indeed, various growth schemes would have filled most of it if the Save the Bay movement hadn’t begun in the 1960s. Jack Foster succeeded in dumping 1.5 million truckloads of rubble into the Bay to make Foster City in 1962. A decade later, David Rockefeller failed to cut off the top of San Bruno Mountain to make a Manhattan-sized Bay island.
Unfortunately, stopping the Bay’s physical obliteration is not enough to save it. Growth has diseased as well as injured it by destroying more than 90 percent of its wetlands, diverting more than 60 percent of its river flows, decimating its biota, and contaminating waters, wetlands, and wildlife with sewage, refinery wastes, pesticide residues, and many other things—an alphabet soup of toxic elements, from arsenic to zinc.
None of the professional Bay-watchers (a research scientist, an environmentalist, a Coast Guard licensed operator, and a boating entrepreneur) who went with me on the inflatable excursion to the Golden Gate doubted for a minute that the Bay was sick and getting sicker. The licensed operator, salty-looking Captain Joshua Mills, saw some improvement in water quality from past decades, when “the water was so black in places you could drop a ham sandwich in it and even a gull wouldn’t touch it.” But he expressed amazement that the Bay had lasted as long as it had, given the pressures on it.
“Improved water quality won’t help the Bay in the long run if all the habitat is lost to development,” said environmentalist John Amodio of the Bay-Delta Preservation Trust.
“Cleaning up sewage and factory discharges won’t even improve water quality if agribusiness keeps diverting more water,” said scientist Michael Herz. “I wouldn’t eat a striped bass out of the Bay now, even if the population wasn’t down 80 percent from the 1960s.”
“I’m afraid the Bay is finished as a commercial fishery,” said recreation entrepreneur Jerry Cadagan, president of San Francisco Bay Adventures. “The San Joaquin River has become a toxic drain. And what’s so frustrating about this is that further water diversion for irrigation isn’t even going to help agribusiness in the long run. It’s just letting them grow crops that are already in surplus while they poison their soil with salt and selenium.”
“The Bay Area is supposed to be environmentally enlightened,” said Amodio, “but there hasn’t been a concerted effort to manage the Bay as an integrated ecosystem. Government bodies have concentrated on their own little fiefdoms, and the conservation