|Publisher:||University of California Press|
|Edition description:||First Edition|
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Down by the Bay
San Francisco's History Between the Tides
By Matthew Morse Booker
UNIVERSITY OF CALIFORNIA PRESSCopyright © 2013 The Regents of the University of California
All rights reserved.
Seen from space, California's coast is a thin white line between the deep blue ocean and the green and brown of a seasonally arid land. In a thousand miles of pounding surf and steep cliffs, only once does the ocean enter deeply into the land. Three great, kidney-shaped bays spread inland and eastward from the ocean, meeting ribbons of water draining snow-capped mountains to the east. The three shallow bodies together form San Francisco Bay, arm of the sea and estuary of the Sacramento and San Joaquin Rivers. From about five miles up—the altitude of a commercial airliner—cities, highways, and farmland come into view. They suggest the widespread presence and influence of human beings on the landscape of the San Francisco Bay Area. Seen from a descending airplane or the hills that ring the bay, the baylands come into focus. At low tide, dark brown mudflats and shallow channels dominate much of the bay surface. A swath of green salt marsh and bulrushes covers the shores of the northern bays, and the ridgetops around the bay are open grassland parks. From this height, a human landscape dominates the bayshore. Cities, suburbs, airports, vast seaport shipping facilities, industrial areas, garbage dumps, salt ponds, and diked farmland extend to the horizon. But from water level, the cities recede and the bay is revealed as an enormous open space largely free of human constructions. If our camera eye drops still lower, beneath the surface of the turbid water, we can see that the foundation of this human landscape is the thick mud of the bay bottom. The cities, the airports, and the farmland all rest on a drowned river valley's silts.
Our descent from the stratosphere to the bay floor reveals a unique natural feature: the only major break in the Pacific coastal wall between Mexico and the Columbia River. This is western North America's most important estuary. Forty percent of the rain and snow that falls on California drains through this estuary into the ocean. Winds blow through the narrow gap in the rampart of the coastal mountains, cooling the interior valleys and producing unique microclimates, fog belts, and windswept hilltops. Water also flows through the gap. Twice each day, the ocean's great tides, heaving up and down in response to the pull of the sun and moon, sweep up into the interior of California and then, with power greater than any river, rush out again. As the tides move through the bays, they mix cold, salty ocean water with warmer, fresh river water. Swirling sediment-laden currents carry this nutrient-rich brew back and forth, upstream and down under the California sunshine, gradually but inexorably toward the sea.
This richness is the product of enormous and ongoing geological change. San Francisco Bay as we know it is a recent and ephemeral phenomenon. The water's edge today laps against a shoreline dozens of feet higher than when human beings first entered the region. At the height of the last ice age, approximately twenty thousand years ago, so much of the earth's water was locked into miles-high glaciers that the ocean beaches lay beyond what are now the Farallon Islands, more than thirty miles from the Golden Gate. About ten thousand years ago the rising sea first pushed through the Golden Gate into the river valleys beyond. For more than five millennia the water swallowed the land and created San Francisco Bay.
San Francisco Bay, then, is a very recent landform. Geologists tell us that the bay's presence is cyclical. During the ice ages, the ocean retreats offshore. And during the interglacial periods—warming periods like the one we are in now—a bay briefly appears. Sea levels have reached present heights only once before, and rarely have they been high enough to come through the Golden Gate at all. The bay we have now is the largest and longest lasting ever recorded. We live at a time of unusually high water, near the top of the tide.
Life on earth ultimately takes its energy from the sun. But sunshine alone does not guarantee life, as any visitor to the desert knows. More than four-fifths of the surface of the earth is open ocean, desert, and ice. These are sunny places. Yet the open oceans, deserts, and polar ice caps are among the most barren habitats on earth. For plants to grow, they must have sufficient moisture as well as light. All celled creatures depend on a handful of key chemicals that are found on the continents. These nutrients are constantly washing away into the sea. The continents are nutritionally poor, and they get poorer all the time. The sea, on the other hand, is too diffuse. The great stocks of minerals eroded from the land are dissipated in the immense volume of seawater covering two-thirds of the planet. Life is most abundant when limiting chemicals—particularly nitrogen and phosphorus—occur in the presence of plentiful sunshine and water. This happens most often on the edges between land and water. And it happens most effectively where rivers carrying their precious cargo of eroded terrestrial nutrients meet the sea. At these estuaries, freshwater and salt water mingle, and rivers drop their loads of rich silt and sand. Thanks to this unique combination of light, nutrients, and topography, as geologist and marsh scholar Nathaniel Shaler observed more than a century ago, "the undersea portion of the beach becomes, of all the water-covered areas, the fittest seat for life." Shaler referred to the tide-washed shoreline. Around the edges of the estuary, shallow-water communities of plants take up the nutrients from the fertile sediments. These are the tidelands, the area of land and water existing between high and low tide.
Life moves with the water. Microscopic plants travel in the water column, blooming in the nutrient-rich, sun-soaked shallows. Diatoms encrusted on flecks of mud and free-floating plankton alike capture the energy of the sun and make it available for creatures small and large. This productivity is concentrated on the edge of the bay. On the margin, salt-tolerant marsh grasses colonize soft mud. The partially submerged grasses break up the tidal currents and shelter myriad creatures. Young salmon come downstream and use the salt marshes and shallows as rearing areas. The young fish grow quickly in these sheltered puberty pools. Crabs and other ocean species move into the brackish bay to mate, giving their young the benefit of the nutrient-rich estuary and its protection. Terrestrial animals feed on the plants and fish in the marshes. Human beings, terrestrial animals ourselves, rely on the estuary's fertility and productivity in many ways, but most directly for the shallow water fisheries. Historically, California's most consistent and most valuable fish species were found in San Francisco Bay.
All of this spectacular richness rests on something quite prosaic. Rivers and streams carry nutrients into San Francisco Bay, and the tides recirculate them. A speck of silt entering the bay from the delta does not continue onward, in stately fashion, to the ocean. The tides, pushing and pulling the bay's water in currents more powerful than any river on earth, carry every cup of river water back and forth from delta to deep bay, up and down in the water column. Between the moment that a drop of muddy water enters the estuary and the instant that it finally leaves the bay for the Pacific Ocean, it may whirl hundreds of miles through the bays and delta. The tides recirculate the water twice daily. This mixing is the key to the bay's fecundity. Thanks to the tides, bay marshlands receive a constant flow of nutrients. The tidal plants never lack, because the bay brings more with every tide.
San Francisco Bay's tidal wetlands, like tidal marshes worldwide, are extraordinarily productive of vegetation. According to scientists, the largest "above-ground standing crop in North America" may belong to bulrushes in the freshwater tidelands of the Sacramento-San Joaquin delta. Growing nine to twelve feet in a year, these rushes annually produce over half a pound of plant matter per square foot, a density nearly unparalleled in nature. Because of the rivers and tides, this amazing richness is not trapped in place. Tiny pieces of plant stems break off and are circulated by the tides. The delta's freshwater tidelands, together with the salt marshes fringing the bays, annually contribute 2.2 billion pounds of fixed carbon to the San Francisco Bay estuary. Carbon compounds are the building blocks of all life on earth. Dissolved in water or mixed in the atmosphere as carbon dioxide gas, available carbon measures how much plant growth can occur. It is a measure of productivity.
Only modern agriculture, assisted by fertilizers and machinery, can match the output of salt marshes. Tidal wetlands exist at the bottom of rivers and top of the ocean, where they build up from fertile soil washed off the land by rainfall. They are sustained by the constant push and pull of the tide, which brings in nutrients and animals and carries away waste. Acre for acre, tidal wetlands convert more sunlight, air, and water to plant matter and animal flesh than any grassland or tropical rain forest. Salt marshes are nature's furnaces, stoking a rich food web that sustains biological communities all over the world.
Despite all this movement, the communities of the tidal margin are relatively stable compared to those of central California's upland habitats. Climate cycles made the valleys and hills sometimes very fecund, but these areas were also prone to extended drought. The bayshore, on the other hand, could be depended upon for food resources during all seasons and in all years. The marshes and shellfish beds did not dry up, burn down, or wash away; they were rare reliable food sources in a feast-or-famine landscape. As a result, these were the places where California's native peoples congregated.
A CROWDED AND CULTIVATED LAND
In 1793, His Britannic Majesty's Captain George Vancouver crept into San Francisco Bay in command of a small flotilla of vessels. Entering the territory of a traditional enemy without permission, Vancouver was relieved to discover that the Spanish fort commanding the imposing south shore of the bay entrance, the Presidio de San Francisco, was defended by only a small band of troops manning a handful of decrepit cannons. After a tense exchange of formal greetings with the Presidio's proud but outgunned commander, Vancouver went ashore with his ship's surgeon, naturalist Archibald Menzies. Menzies was eager to compare the plants and animals of this unknown coast to his collections from elsewhere in the north Pacific, but he contented himself with exploring the long lagoon behind the sandy beach near the Presidio. Vancouver, meanwhile, began a busy round of social activities and surreptitious spying. He dined with the officers of the Presidio, ogled their wives and daughters, and visited the nearby Mission San Francisco. Vancouver and his lieutenants borrowed horses from their hosts to visit Mission Santa Clara at the south end of the bay. The party picnicked in a grove of oaks that reminded Vancouver of an English park. Surveying the brown autumn hills and plains, dotted with majestic oaks and occasional streams, the Englishman saw a landscape that recalled familiar European places, and that seemed equally imbued with promise. But, Vancouver judged, the Spanish were neglecting this potential. After a quarter century of Spanish religious instruction and economic guidance, the Indians, the laborers of the region, "still remained in the most abject state of uncivilization." Only the introduction of "foreign commercial intercourse" could "stimulate the Indians to industry," asserted Vancouver.
Neither Vancouver nor his lieutenants recognized that human hands had already shaped the shores of San Francisco Bay. Archibald Menzies was a professional naturalist and a keen observer of Pacific coastal habitats whose name graces many of the region's plant species, including the most common conifer, the Douglas fir, Pseudotsuga menziesii. Yet Menzies had little to say about the salt marshes and shoreline plants of San Francisco Bay. Partly this was due to his unfortunate timing. November is among the least rewarding times to see San Francisco Bay's rich diversity of flowering plants. And the salt marshes, in any case, are not laden with bright flowers. Their beauty is found more in shades of green, grey, and brown: the sort of beauty revealed by winter, a beauty of the bone. Menzies's eye wandered past the salt marsh and up toward the brown hills, which he so badly wanted to see in bloom. Like other nineteenth-century European visitors to San Francisco Bay, Vancouver and Menzies hardly noticed the marshes lining its shore. These men saw the bay as a world apart from the land, and it was the land that interested them for its potential agricultural bounty.
When we read Menzies's, Vancouver's, and other Europeans' descriptions of San Francisco Bay, we can be fooled, as they were, into thinking that neither Ohlones nor the Spanish and Mexicans who lived among them manipulated their natural surroundings. It would be a grave mistake to repeat this error. The Indians and Spanish did change the landscape, just not in the ways that English visitors expected. In recent years, a group of historical ecologists has shown that San Francisco Bay's tidal margin contained a remarkable diversity of habitats ranging across a spectrum from salty and marine to freshwater and terrestrial. Many of these habitats were made or maintained by human beings. The bunchgrass prairies and parklike oak savannahs, for instance, that so captivated Vancouver's men on their ride to Mission Santa Clara, would have been overgrown by brush without frequent fires set by Indians. Ohlones maintained these grassy plains with their widely spaced majestic oaks. Native peoples surely also modified tidal and aquatic habitats. Like other coastal peoples of the Pacific, Ohlones used the shoreline intensively. They harvested fish, shellfish, and other food resources from the marshes and bay waters. They built fish traps and shot and netted waterfowl. Historians and ecologists have also speculated that native peoples enhanced naturally occurring salt evaporation ponds to improve their harvests of the precious mineral, which they traded with inland peoples. Ohlone oral tradition recalls some of these practices and their purposes in a social world whose heart was the water's edge.
A LANDSCAPE OF SHELLMOUNDS
California's first humans arrived during the final millennia of the last ice age. They probably came by water. The oldest archaeological sites are from islands off the central California coast and from inland sites not far from the coast. It is very likely that people lived in the river valleys before San Francisco Bay covered them. Their campsites, their villages, and their burials are now themselves buried by thousands of years of tides and silt. What is certain is that the bayshore has been home to thousands of people for thousands of years. As late as the twentieth century, hundreds of mounds dotted the bay's edge.
Much of what modern scholars know about San Francisco Bay's native peoples derives from the waste they left behind. Native peoples built hundreds of mounds around San Francisco Bay from the shells of mollusks they collected from the bayshore. These mounds, which ranged in size from a few yards to dozens of yards in diameter, were more than just middens, or kitchen garbage. Most of the few large mounds excavated contained human remains buried in ritual fashion, and they clearly served multiple purposes for the peoples who built them over long centuries. Archaeologists excavating the shellmounds have constructed a cultural history of human use of the bayshore for at least three millennia and thousands of years longer farther inland. As Joe Eaton notes, "There are places in California with the time-depth of Troy or Jericho." Scholars can only speculate on how such intensive harvest may have influenced favored shellfish species, but it is clear that Indian people were huge consumers of marsh and mudflat animals.
The Ohlone economy was local, personal, knowledgeable, and communal. It was part of a flexible economy adapted to unpredictable cycles of rain and drought. These were people who knew intimately the productive places and seasons of the baylands. Native peoples harvested so many shellfish that they built hundreds of huge mounds around the bay. In 1906, University of California scholar N.C. Nelson found that, despite decades of destruction by farmers and road builders, several hundred mounds still remained. The shellmounds held deep cultural meaning for Ohlone people. Some mounds held hundreds of burials, with bodies carefully oriented and accompanied by special objects. It is one of the great tragedies of California history that so much of the meaning of these spaces has been lost. Yet even stripped of their context the shellmounds are testimony to the tremendous productivity of the tidelands and their central place in the indigenous economy. Far from subsisting solely on the acorn, deer, and salmon that anthropologists once assumed were the basis of all California native economies, Ohlones used resources from every part of their landscape, from peaks to bay. At the center of their lives lay the bay's edge. As Europeans colonized California, they destroyed native economies by limiting Indian access to the most important resources, which lay along the bayshore.
Excerpted from Down by the Bay by Matthew Morse Booker. Copyright © 2013 The Regents of the University of California. Excerpted by permission of UNIVERSITY OF CALIFORNIA PRESS.
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