San Francisco Without the Bay

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WITHOUT THE BAY, the San Francisco Area would be much like the rest of Central California. The existence of this grand estuary made the Bay Area the most populous part of the state for much of California's history. The Bay defines the lives of people living nearby, whether they're commuting under, over, or around it, spending extra money to live in a place with a bay view, or enjoying (or cursing) the cool weather the Bay engenders.

On a map, the Bay is a patch of blue, with clear boundaries, between the Golden Gate and the Delta. In real life the Bay's boundaries are harder to define. Even after a century of relentless filling, dredging, and diking, it would be hard to draw a line around the Bay outside of which nothing of the Bay remained. The Bay's influence reaches far beyond the 550 square miles of open water and tidal lands called the San Francisco, San Pablo and Suisun Bays.

In a sense, the Bay extends out through the Golden Gate, along with the silt-laden water it discharges into the Gulf of the Farallones, adding rich nutrients from Sierra Nevada slopes and Delta marshes to the ocean, feeding the plankton that feed the fish that feed the seals that feed the great white sharks. The Bay's influence on weather extends to Yosemite and Mammoth, with its extra foot or so of snow, courtesy the low, moist pass through the Coast Ranges the clouds went through on their way to the high country. Forty percent of the state of California, from Mount Shasta to Mount Whitney, drains through the Golden Gate. The Bay is hydrologically linked to every square inch of this immense watershed.

Though its outward boundary is hard to determine, the San Francisco Bay and Delta Estuary holds a nested set of internal boundaries that are somewhat more obvious. Freshwater marsh, salt marsh, mud flat and open water, all with their distinct characteristics, are the varied terrains that make up the estuary. The distinctions among these four habitats are quite marked. The physical boundaries between them are fluid, shifting with the tides, the seasons, and longer climatic cycles, but those boundaries are still there. Much of the biodiversity the Bay can claim stems from the interaction of these boundaries, in what ecologists call the "edge effect." Where plants and animals from one habitat encounter those from another, unique ecological "job opportunities" arise.

Before we tried to tame the shore with erosion control projects, broad flatlands subject to twice-daily flooding made up most of the land-water boundary. Higher ground was laced with an intricate network of sloughs, creeks and embayments fringed with Townsend's cordgrass. Edge effect notwithstanding, the Bay is not too biologically diverse compared to a tropical forest or a coral reef. But what the estuary may lack in number of species it makes up for in tons of biomass per acre, chiefly due to the astonishing productivity of cordgrass. Growing just below the level of mean high tide, cordgrass forms a sieve that captures debris borne by tides or creeks. Cordgrass provides organic matter of its own, as well, producing between three and ten times as much per acre as a field of wheat.

The Salt Marsh

Salt marsh plants have had to evolve defenses against the very medium that sustains them: salt water. Cordgrass adapted to its toxic growth medium by evolving glands that pump salt out of the plant to dry in a crystalline coating on the outside of the stems and leaves. This coating then helps protect the plant; not many organisms can eat live cordgrass without taking in too much salt themselves. Fresh water distilled by the cordgrass plant is kept inside the leaf. Salt-tolerant plants like cordgrass provide a source of fresh water for other plants, such as dodder, a parasitic plant, whose roots draw nutrient-laden fluid from its host. Like most successful parasites, dodder is usually only a minor hindrance to the growth of its host plants. Taking too much would endanger its own long-term survival.

When cordgrass drops its leaves, seeds, or old stems, they fertilize other plants and feed the animals who eat decaying plant matter. Their wastes and discarded bodies contribute further to the fertility of the salt marsh, providing food for other marsh inhabitants. The salt marsh harvest mouse spends its life turning used vegetable matter into mouse flesh. As water levels surge in winter and Rood harvest mouse homes, the mice head for higher ground, only to be "harvested" by herons, gulls, and hawks. Solar energy thus flows from cordgrass through the mouse into the flesh of the animals that eat mice. Each year, most of the harvest mouse population makes its way into the stomachs of other animals. Harvest mice can breed at six weeks old; the mouse population has at least four generations to recover after each harvest, helping to ensure not only the continued existence of the species but also a seasonal glut of food for predatory birds. Unfortunately, the resiliency of the mouse depends as much on the continued existence of salt marshes as on the fertility of the mice: between 85 and 95 percent of the mouse's habitat has been destroyed by filling, or by dilution of salt water in the marshes by fresh water from sewage outfalls. Due to habitat loss and introduced predators, this linchpin of the salt marsh food chain is now listed as an Endangered Species.

The California clapper rail, the harvest mouse's co-tenant in the salt marsh and the Endangered Species List, eats clams, mussels and crabs that live in and under the tall marsh grasses. The rail's long beak is an effective tool for prying mollusks from the muck, as well as for extracting bits of crab from deep inside the shell. Its dusky brown plumage, similar in color to the harvest mouse, effectively hides the rail from predators.

Camouflaged or not, the rail was a common sight to early European settlers of the Bay Area. The cordgrass marshes and the tidal lands beyond held mollusks ranging from snails to octopi. Crustaceans were well represented too, including the hermit crab, well known for recycling vacated shells of other animals into its own shelter. Abundant rail food meant abundant rails. Things have changed. The clapper rail went into decline as European settlers filled the marshes that are its habitat. Biologists estimate that fewer than five hundred clapper rails now survive.

The Most Dynamic Boundary

The tides that inundate the salt marsh push a wall of seawater upstream, past Point Pinole and the Carquinez Strait, into the Delta, where the Sacramento and San Joaquin Rivers drain four mountain ranges into the Bay's drowned river valley. The boundary between salt water and fresh is one of the most dynamic the Bay holds, changing shape and location from hour to hour. Upstream from this boundary, freshwater marshes host abundant life.

The relative absence of tides and their daily scouring effect, and the more hospitable nature of fresh water, mean that the boundary between marsh and open water is more vague here than in the salt marsh, with its plantless skirt of mudflat. Plants that can survive without being rooted in soil, such as duckweed and the invasive water hyacinth, ring the marsh in floating mats. Proceed landward, and you pass distinct bands of plants each with their own preferred water level. Tule, the signature plant of the Central Valley, forms thick tangles where the water is a foot or so deep. Further uphill are smaller rushes, bulrushes and sedges. A band of cattails, which can't tolerate continuous wet feet, marks the outer edge of the freshwater marsh, fringing what biologists call riparian (streamside) habitat, with its willows and elders and alders.

Freshwater marshes and riparian habitat aren't just found in the Delta. The Sacramento and San Joaquin are only the largest of the estuary's rivers. Smaller rivers and creeks, from the Napa to the merest seasonal trickle flowing into the Bay, support freshwater marshes where the water is constant, and riparian plants and animals where it's a bit drier. These creeks and rivers were vital to the Bay Area's first people, the Ohlone. Streams provided drinking water, and fish like salmon and trout. Where freshwater marshes were large enough to support a stand of tules, they were harvested to be turned into the Ohlone's characteristic vehicle, the tule raft. These canoe-shaped bundles of stems were seaworthy enough to carry people across the Bay. When they were old and battered by exposure to the elements, the boats were left to break down into organic matter, their nutrients returned to the Bay's ecosystem.

The Ohlone of old would no doubt be stunned to see the changes in the creeks they so relied on, For years, urban planners regarded creeks as nuisances, breeding grounds for malaria, places for illegal trash dumping. Most of the Bay's creeks have been at least partially buried, channeled, or drained. But as we learn more about the importance of creeks, not only to wildlife but also to our own emotional well-being, more and more people are working to restore the creeks in their neighborhoods. In industrial and residential areas, near schools, and -- poetically -- on land owned by present-day Ohlone people, volunteers are unearthing these living veins of the Bay watershed. Replanting native vegetation, clearing trash, or painting warnings not to dump motor oil in storm sewers, we learn how we can live with our creeks in a more sustainable way.

Cycles of the Delta

In the Delta or at the mouth of a small creek, the meeting of ocean and river creates a dynamic balance between freshwater and brine, the biologically-rich ,,mixing zone." Before farmers and city-dwellers claimed much of the fresh water in the watershed, this zone shifted in daily and monthly tidal cycles, with lunar pulses of salt water from the ocean, and with the seasons, as winter storms and spring runoff charged the estuary with fresh water. The delta smelt, at one time one of the most common fish in the estuary, rode this mixing zone back and forth, living off the rich brew of marine and river plankton. Smelt are kin to salmon, and the delta smelt shows this relationship in its life cycle. It begins its life in fresh water, moves to saltier water to grow to adulthood, then returns to fresh water to spawn and die. The ecological peril in which the smelt finds itself stems in part from the fact that its migration covers not thousands of miles of western river and ocean floor, but the fifty or so miles from the upper delta, reaching from Stockton to Sacramento, to the mixing zone in the environs of Suisun Bay. The smelt has tied its life cycle so tightly to the hydrologic balance of the Bay and Delta that water diversions have all but erased it from the planet. When lots of water is diverted, the mixing zone moves upstream into the Sacramento and San Joaquin Rivers, much narrower channels than the smelt would find in the broad expanses of Bay and Delta. The water here is swifter and deeper, too; smelt prefer shallow, slow water. There just isn't enough good habitat to support more than a few smelt.

Back downstream, bayward of the wall of cordgrass that defines the deep edge of the salt marsh lie tidal mud flats and open water. The plants that live here are either marine algae or eelgrass, a descendant of flowering land plants, whose ancestors, like the ancestors of dolphins, headed from the land back into the sea. Invertebrates eat these marine plants, and are eaten themselves by birds like the dunlin and western sandpiper.

A Shallow Saucer Lined With Silt

The boundary between mud flat and open water is not as marked as you might think, though one area is often visible and the other is hidden by water. Except for a couple deep channels-like Raccoon Strait between Angel Island and Tiburon, through which the Sacramento flowed to the sea before the Bay was flooded -- the Bay is a shallow saucer lined with silt, the sediment of 25 thousand years of erosion from the watershed. Hydraulic mining in the nineteenth century and our twentieth century farms and construction projects have added more silt to the Bay.

Silt provides habitat for animals who filter through it for food, tunnel in it for security, or live on the other animals who live there. One of the best-known siltdwellers is the innkeeper worm, which tunnels out U-shaped burrows in the mud whose entrances may be as much as a meter apart. The innkeeper builds a network of mucus in its burrow, then consumes it after smaller organisms have gotten stuck in the tendrils. Weaving and then eating its funnel-shaped "web," the worm moves slowly from one end of its burrow to the other.

The innkeeper derives its name from its tolerance of other animals in its burrow. Innkeeper's "inns" provide shelter and table scraps for crabs, other worms, and fish such as the arrow goby, which dives into the burrow when threatened. Several gobies may simultaneously use an innkeeper's burrow.

Dwellers in the shallows are eaten by larger animals, some of which are among the most dramatic inhabitants of the shoreline. The great egret, which eats invertebrates, fish, and the occasional harvest mouse, is one such. Standing about three and a half feet tall, the great egret's ghostly appearance has startled many a casual observer with its snow white plumage and slow, deliberate motion. They seem not to spook easily, and several traffic jams on Bayshore freeways have resulted when drivers slow down to see egrets reproaching them from the shoulder. Well may they reproach; the great egret was driven nearly to extinction in the twentieth century because we decided its feathers looked nice in hats.

The Ohlone took advantage of the mudflats, too, eating the clams and mussels and oysters that lived there. When Europeans first came to the Bay, they were greeted by huge shellmounds, "landfills" where Ohlone people had discarded empty shells. One of the largest, in present-day Emeryville, was fifty feet high and covered a city block. Contrast this mound, built over hundreds or thousands of years, with our much larger landfills around the Bay shore, made in less than a century, and the impact of Ohlone life on the environment seems low indeed.

Where the water is too deep for the tides to uncover the mud, the brown pelican makes its living eating sardines and other small fish. During the middle of the twentieth century, a decline in brown pelican numbers was noted, not just in the Bay but nationwide. Widespread use of an insecticide, DDT, had put the chemical into just about every ecological niche there was, including the Bay and the fish swimming in it. Pelicans ate those fish, consuming DDT. The pesticide interfered with the flow of calcium from fish bones to pelican egg shells; pelicans laid eggs with weaker shells, which crushed when sat upon. In 1970, only three young brown pelicans were reared in all of California. A DDT ban in the US and migration of pelicans from Mexico have brought their numbers up; it is no longer rare to see groups of the birds flying in strings of a dozen just above the surf. But habitat destruction and continued pollution may yet undo their recovery.

Spurred to Action

It isn't just birds who suffer from eating polluted fish. People who fish from piers and jetties around the Bay take heavy metals and other toxins into their bodies when they eat their catch. Spurred to action by the threat to their health, anglers have been persuading corporations and utilities to monitor their discharges into the Bay more closely.

Even before we started polluting the Bay, fish had to contend with water quality. The salinity of the Bay varies from point to point, from season to season. Fish restricted to fresh water don't do too well further out into the Bay than the mixing zone; ocean-going fish like sharks may find the water past Point Pinole a bit too brackish for their taste. An exception to this rough rule can be found in anadromous fish, like the salmon and steelhead, which spend most of their lives in salt water, but are born in fresh water and return to fresh water to breed. The largest of the Bay's salmon, the chinook dominated the streams surrounding the Bay when it spawned. The Sacramento-San Joaquin drainage marked the south end of the chinook's range.

Our habit of burying creeks and damming rivers has essentially ended chinook use of the Bay Area. But before urbanization, the chinook and its relatives were an important vehicle by which the ocean distributed its riches on the land. Heading up small streams to spawn, the fish were often eaten by large land animals like grizzlies, wolves, coyotes, and humans. Those salmon that made it to the headwaters and spawned soon died, and scavengers such as black bears and golden eagles redistributed their organic matter throughout the land near the headwaters, where it fertilized the soil. Thus the biological wealth of the deep ocean, the squid and the sardines and the jellyfish that the chinook had eaten while prowling the depths of the Pacific, were redistributed among the feeder streams of the Bay's watershed. The flow of nutrients from mountain to ocean was, in part, reversed. Fertile eggs left behind would hatch, the salmon fry remaining in fresh water for up to a year before heading out into the Bay and thence the ocean, starting the cycle anew.

The salmon's homing instinct still mystifies scientists. No one knows quite how this fish navigates its way from deep ocean, into the Bay's hidden entrance, and up hundreds of miles of river and stream to precisely the same small watershed in which it hatched. Fortunately for the fish, they don't depend on us to teach them how to find their way. Before damming of rivers got underway in the last century, each brook, each rill contributed its population of salmon to the ocean. After a time, those of them not eaten by larger ocean fish would return, finding the Bay; mature fish heading for the Modoc Plateau swimming shoulder to shoulder with their colleagues bound for the southern Sierra Nevada. Trace the paths of the fish, and you trace the massive network that is the Bay's watershed.

The salmon might see the Bay as a mere rest stop on their epic journey. The innkeeper worm might see it as the whole universe; terra firma below and a beneficent watery sky above. Salt marsh harvest mice no doubt perceive the Bay as a hostile frontier, pelicans seeing the same expanse as a hospitable larder. The Bay is less a thing than a meeting place, where rock from above treeline in the Sierra meets silt upwelled from the deep, where salt water meets fresh in a game of tag from Antioch to the Farallones. It's a heart that pumps life into millions of sloughs, Rats and channels. And though we've put airports and landfills where cordgrass once supported billions of living things, and though we've fouled it with our industrial discards, the Bay still lives. it is poisoned and encumbered, but we have not yet stopped this heart of California.