Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 8
Chapter 9
Chapter 10
Main
06/26/98 Draft Report
Process for Establishing Goals
Key Species and Communities
Key Habitats of the Baylands Ecosystem
Baylands Habitats, Past and Present
Technical Considerations for Habitat Restoriation
Monitoring and Research
Implementation Issues
PDF Version
San Francisco Estuary Baylands Ecosystem Goals Draft Report for Public Review June 26, 1998 |
| A Picture of the Past |  |
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The view of the past illustrates the bays, baylands, and adjacent habitats as they would have appeared to native peoples who inhabited the landscape at the time of European contact. Perhaps as many as 50,000 people lived here at that time, in thirty or more distinct tribes.
To describe the estuary under native conditions, we might start in the bays, moving progressively towards shallower habitats along the shore. The deep parts of the bay contain the submerged topography of ancient valleys, following the old river courses draining the Santa Clara Valley and the Central Valley. Suisun Bay, the North Bay, and the South Bay were dominated by shallow waters, while the steeper Central Bay was relatively narrower and deep. Together the deep and shallow bays totaled approximately 250,000 acres, roughly the same amount as the adjoining baylands.
At low tide, 50,000 acres of tidal flats emerged from the water at the edge of the shallow bays. The flats were as wide as two miles in the South Bay. Under fresher conditions in Suisun and North Bay, where marsh plants colonized the lower intertidal zones, there were only a few, relatively small tidal flats.
See maps, Figure 6.1 Past and Present Distribution of Baylands and Adjacent Habitats
Habitat Management Past and Present
Near present-day Hayward in the South Bay there used to be transitional pannes twice as large as any others in the region. The Yrgin Ohlone apparently managed these pannes to make salt. Salt crystals were collected from willow sticks placed in the briny waters. The earliest Spanish missionaries adapted the native salt harvest practice and used the Ohlone to harvest the salt. Did the Ohlone engineers modify the ponds for salt production? Were there weirs or gates to control the tides?
In the North Bay, near present-day Novato, the Omiomi Coastal Miwok lived beside some unusually large tidal marsh ponds. There is evidence to suggest that the Coastal Miwok may have created and managed these ponds for waterfowl hunting. Less than a century later, European immigrants began to hunt ducks on tidal marsh ponds, a practice that later gave rise to duck clubs, as the marshlands were reclaimed for agriculture. To what extent does modern-day duck club management reflect the practices of the coastal Miwok?
About 200 feet upslope of the tidal marshes of Petaluma there were three large features called lagunas or shallow lakes. They are unlikely to have been natural features because they occupied sloping valleys with small catchment basins in a region with more potential evaporation than rainfall, and they emptied through narrow drainages into steep streams. It is more likely that the lagunas existed because of low dams that crossed the narrow drainages. Thousands of native people lived more or less directly downstream of these features for almost 50 centuries, under similar climatic conditions as today. Were these features perhaps created for hunting and fishing, or to deal with drought and deluge?
Within the estuary, sandy beaches were common only in the Central Bay, where about 15 miles of narrow beach fringed the marshes and flats. Associated with some beaches were natural tidal lagoons, particularly along the San Francisco peninsula and Marin shoreline.
Landward of the flats and beaches there were almost 200,000 acres of tidal marshland. In Suisun, the North Bay, and the South Bay, vast contiguous marsh plains extended across 50,000 or more acres, divided only by tidal channels. In the Central Bay, tidal marshes were much smaller, from tens of acres to several thousand acres, due to the steepness of the topography.
Tidal marshes were more saline towards the Golden Gate and fresher towards the mouths of creeks and rivers entering the estuary. Superimposed upon the major estuarine gradient extending from the Golden Gate to the Delta, numerous smaller estuaries were associated with local creeks. Here, decreasing tidal salinity resulted in shifts in the plant communities and structure of marshes. Brackish zones extended several miles from the mouths of larger creeks like Napa, Alameda, and Coyote.
Large tidal channels connected the marshlands to the bays and spread into a network of thousands of smaller and smaller channels distributed throughout the marsh. At their mouths, the major channels were several hundred feet across; the huge volume of water that flowed in and out of the channel network during each tidal cycle maintained deep and shallow channels through the marsh, flats, and bays. In some parts of the estuary, large channel-side flats extended up the channels.
Looking at the marshlands from an adjacent hill, one would see hundreds, or thousands, of shallow ponds scattered between the sinuous channels. These natural ponds ranged from tens of feet in diameter to, in the case of the Sixth-Reach Pond in Suisun, two-thirds of a mile long. Ponds were smallest and most numerous in the salty parts of the estuary and larger where the tides were more brackish.
Where the tidal marsh met the edge of the land, there were elongate, transitional pannes. In the South Bay, these apparently formed a nearly continuous sequence of pannes from the Yrgin to the Ssalson regions. Some pannes were managed for salt production and perhaps waterfowl habitat. One of these, the Crystal Pond complex, in the Yrgin tribal region, was over 1,000 acres in size.
In the flattest valleys, the tidal marsh graded gently into low-lying moist grasslands. Creek deposits of very fine clay created patches of poorly drained land. Where the winds across the Bay were strongest, they extended the influence of salt inland, widening the tidal marsh/upland ecotone. Near Fremont, Sonoma, and the Potrero Hills, impervious soil resulted in grasslands with vernal pool complexes reaching to the upland edge of the tides.
In this semi-arid region, perennial freshwater resources were limited. The greatest amounts of persistent freshwater features (ponds, lakes, and willow groves) occurred in the particularly flat valleys of Santa Clara and Walnut Creek. Scattered but important freshwater features were also found in places where groundwater emerged at the edge of the tidal marsh and in ponds along faults, particularly along the San Andreas and Hayward faults in the South Bay. In the North Bay, Lake Tolay, an unusual feature in the hills between the Sonoma and Petaluma marshlands, covered several hundred acres, many times more than the cumulative total of all other North Bay perennial surface waters.
Narrow riparian forests followed the larger creeks to the edge of the tides; on other creeks riparian trees were scarce. Many of the creeks did not reach the bay, but fanned out in the lower alluvial plain, often into willow groves. Willow groves, known as sausals to the Spaniards, were common at low elevations near the marsh in the Central Bay and South Bay. In the South Bay, some of the willow groves were more than 200 acres.
The marshland, willow groves, riparian forests, and moist grasslands comprised complex mosaics of habitats along the bayward margin of local watersheds throughout the region. The local complexity and wealth of habitats and native resources was reflected in the richness and diversity of native languages.
| Historical Development And Wetland Losses | |
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Beginning in the mid 1800s, large areas of tidal marshes and mudflats of the estuary were filled, drained, or diked. Extensive portions of the baylands were filled to provide land for ports, rail lines, and roads as the Bay Area became a major transportation center. Much of the early industrial development of San Francisco, Oakland, and other shoreline cities was built on or adjacent to the Bay.
Farmers began diking and draining the Bay's tidal marshes in the 1850s. Initially, levees were small and the scale of reclamation was limited; but, by the 1870s, commercial dredges enabled the construction of larger levees. By the 1920s or 1930s, most of the historical tidal marsh areas of Suisun and the North Bay had been converted to agriculture.
Initially, most of the diked historic baylands in Suisun were used for livestock grazing. In the eastern portion, however, some truck crops also were grown. Eventually, as land subsidence made it difficult to regulate groundwater levels and soil salinity, duck clubs displaced nearly all but about 1,500 acres of oat hay fields. Many of the levees originally constructed to enable farming in the baylands are today an integral part of the infrastructure for managing water levels in the duck clubs.
| Figure 6.2 Past and Present Acreages of Habitats Project Area | |
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Bay
Baylands
Adjacent Land
In the North Bay, livestock grazing was the sole agricultural practice on the diked baylands for many decades, as the high water table and soil salinities discouraged the production of truck crops there. In the past two decades, farmers have shifted toward the production of silage for dairy cattle, but oat hay farming continues, primarily for horses. Recently, several farmers established vineyards on the edge of the baylands. In total, there are about 25,000 acres of baylands in the North Bay that are, or recently were, in some form of agriculture production.
The diking of Bay marshes for salt production began around 1860 and continued for nearly one hundred years. By the 1930s, about one-half of the South Bay's tidal marsh area had been transformed to salt ponds. By mid century, salt ponds had replaced nearly one-fifth of the historical tidal marsh area in the North Bay. By the 1950s, only about 50,000 acres of the Bay's original (circa 1800) 190,000 acres of tidal marsh remained intact. Since then, tidal wetland losses have continued, although at a much lower rate than previously.
Today, there are about 40,000 acres of tidal marsh remaining in the Bay, and most of these marshes are degraded. Many have had their upper portions filled as development pushes to the Bay edge. Many, especially in the South Bay, have subsided and/or have undergone major vegetational changes due to altered salinity regimes. Others have become narrow, fringing marshes with little overall habitat value.
The loss, conversion, and degradation of baylands habitats have had a major impact on the baylands' communities of fish and wildlife. This is reflected, in part, by the large number of baylands wildlife species that are protected under the state or federal endangered species acts, and by the many other baylands species that are experiencing population declines. For example, in 1992, there were 44 species of baylands amphibians, reptiles, birds, and mammals listed, or candidates for listing, as threatened or endangered.
Of all the changes to the baylands habitats, the filling of tidal areas for urban development has been the most damaging because it eliminated the natural functioning of tidal marshes and mudflats. Converting tidal marsh to farms and salt ponds was less severe, as these diked areas continue to provide limited support for some baylands species, especially shorebirds. On a positive note, farms and salt ponds are excellent habitat for many other species of wildlife that previously had not flourished in the region.
Development also has had a severe, but much less well documented, impact on the area's non-tidal wetlands. About 30 percent of the land in the nine Bay Area counties is now in urban use, and this has resulted in the loss of much seasonal and perennial wetlands and riparian vegetation.
| Comparing the Past to the Present | |
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Today, the amounts of baylands habitats differ greatly compared to the past (Figure 6.2). In the Bays, deep and shallow bay habitats have decreased from about 270,000 acres to about 250,000 acres, reflecting the raising of the bay bottom caused by the deposition of sediment from Sierra Nevada hydraulic mining operations. In the baylands, tidal flat habitat has decreased from about 50,000 acres to about 30,000 acres, mostly a result of bayshore fill projects. The area of tidal marsh has declined from about 190,000 acres to about 34,000 acres, primarily a result of its conversion to managed marsh, farmed baylands, and salt ponds. It is interesting to note that in some parts of the estuary, particularly in Suisun and in San Pablo Bay, tidal marsh actually expanded bayward on newly deposited mining sediments. Overall, however, there has been a drastic reduction in the total area of tidal marsh; according to the data in Appendix C, the amount of tidal marsh in the Project area has declined by 82 percent. In total, nearly 50,000 acres of the historic baylands have been filled.
The Changing Baylands
Beginning in the mid 1800s, tens of thousands of acres of tidal marsh were diked, or reclaimed, for agriculture and other purposes. This resulted in shoaling of the tidal channels that had connected the marshes to the Bay, and the channels filled or became fringed with new mudflats and tidal marsh. Later, the increased supply of sediment from hydraulic gold mining in the Sierra Nevada Mountains helped fill the tidal channels that remained between the diked baylands, and caused shallow bays to grow into mudflats, while deep bays became more shallow. Some of the mudflats built by hydraulic mining debris evolved into tidal marsh, and some of this new marshland was again reclaimed for agriculture and urban development by a second generation of dikes.As a result of this historical diking and sedimentation, the baylands today are actually larger than in the past. They also now support habitats such as seasonal ponds and grasslands that historically were found farther from the Bay.
Today, the baylands include a greater diversity of habitats than in the past. Some habitats, such as salt ponds, are valuable for many baylands wildlife species. However, others, including farmed, grazed, and ruderal baylands are generally more upland in character than the marshes they replaced, even though they support important habitats such as seasonal ponds. Overall, most biologists would agree that, compared to their undeveloped condition, the baylands today provide greatly reduced ecological benefits.
Adjacent to the baylands, farming and urban uses have decreased the area of moist grassland from about 60,000 acres to about 7,000 acres. These developments have likewise reduced the area of grassland/vernal pool complex from about 24,000 acres to about 15,000 acres. Along the streams that bring freshwater to the baylands, riparian forest has declined from about 2,300 acres to about 700 acres, and nearly all of the isolated willow groves have been eliminated.
| Suisun Subregion | |
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The Suisun subregion is the subregion furthest upstream in the Project area. It extends from near Chipps Island on the Sacramento River downstream to the Carquinez Bridge. On the north side of the River is Suisun Marsh, and on the south side is the Contra Costa shoreline. Its major streams include Green Valley Creek, Sacramento River, Solano Creek, and Walnut Creek. This subregion is within Contra Costa and Solano counties. Its baylands include about 74,000 acres.
As its name implies, Suisun Marsh was once an enormous area of tidal marsh. Soil and water conditions in the eastern portion of the marsh tended to be fresher than in the western portion, although salinities were highly dynamic from year to year. In years of high freshwater outflow from the Central Valley streams, Marsh salinities were low; in extended periods of low outflow, the Marsh became much more saline.
In the western portion of the Marsh were hundreds of natural marsh ponds, large and small, that provided excellent habitat for shorebirds and waterfowl. Above the high marsh/upland ecotone were vast expanses of grasslands, about half of which were moist. Extensive areas of grassland with vernal pools also existed north of Potrero Hills and along the Marsh's east boundary.
On the Contra Costa side of the subregion, brackish tidal marshes fringed the shoreline and extended into the lower reaches of the major tributaries. These marshes were particularly extensive in the Walnut Creek watershed which also supported extensive riparian vegetation.
Comparing historical to present conditions in this subregion, deep bay and shallow bay habitats have declined from about 41,000 acres to about 34,000 acres. Much of this change resulted from a general shallowing of the bays that was caused by sediment deposition from Sierra mining some of the deep areas became shallow bay, and some of the shallow areas became tidal flats. With this change, one would expect an increase in the total area of tidal flat in this subregion, Interestingly, however, the current acreage of tidal flat (1,200 acres) is about one-half of what it was in the early part of the 1800s. This seeming anomaly is explained by the progradation, or expansion, of tidal marsh onto the mining sediment deposits in the late 1800s and early 1900s.
In this subregion, tidal marsh has declined from about 65,000 acres to about 9,000 acres, mostly a result of diking. Much of the area of historical tidal brackish marsh has been managed for many decades as diked managed marsh. Adjacent to the baylands, farming and other activities have affected most of the moist grassland habitat and about one-third of the area of grasslands containing vernal pools. Likewise, farming and stream channelization have greatly reduced the area of riparian vegetation and willow groves.
On the Contra Costa shoreline, most of the tidal marshes have been diked, initially for farming, and some have been filled for urban uses. Riparian vegetation has been removed along many of the streams; this change is most apparent in the heavily urbanized Walnut Creek watershed where many miles of stream channel are now lined with concrete.
Figure 6.3 displays the past and present acreage of the key habitats in the Suisun subregion. Compared to historical conditions, tidal flat habitat has declined by 53 percent, and tidal marsh has declined by 86 percent.
| Figure 6.3 Past and Present Acreages of Habitats Suisun Subregion | |
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Adjacent Land
| North Bay Subregion | |
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The North Bay subregion encompasses the baylands and adjacent habitats of San Pablo Bay. Its boundary with the upstream Suisun subregion is the Carquinez Bridge. Downstream it abuts Central Bay on the west shore at Point San Pedro and on the east shore at Point San Pablo. Its larger streams include the Napa River, Sonoma Creek, Petaluma River, Novato Creek, and Gallinas Creek. Lands within this subregion are in Contra Costa, Marin, Napa, Solano, and Sonoma counties. Its baylands include about 80,000 acres.
In the past, this subregion supported large areas of tidal marsh in the Napa, Sonoma, and Petaluma River watersheds, and along Novato and Gallinas creeks. In many places, the tidal marshes intergraded with the uplands in a wide transition zone. Above this zone were oak woodlands, with some evergreen forest on the wetter, north-facing slopes. Seasonal wetlands, including vernal pools, existed in the Petaluma River and Sonoma Creek watersheds.
Most of the baylands within the North Bay have been diked for use as pasture, hayfields, or salt ponds. Other areas support urban or light industrial land use. Overall, however, the North Bay subregion is still largely undeveloped, and it offers many opportunities for restoring tidal marsh and enhancing seasonal wetlands.
Figure 6.4 shows the past and present acreage of the key habitats in the North Bay subregion. Compared to historical conditions, tidal flat habitat has declined by 32 percent, and tidal marsh has declined by 71 percent.
| Figure 6.4 Past and Present Acreages of Habitats North Bay Subregion | |
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Adjacent Land
| Central Bay Subregion | |
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The Central Bay subregion includes the main body of San Francisco Bay. It extends along the west shore from Point San Pedro to Coyote Point, and along the east shore from Point San Pablo to the San Leandro Marina. Its major streams, all relatively small, include Codornices Creek, Corte Madera Creek, Temescal Creek, and Wildcat Creek. Lands within this subregion are in Alameda, Contra Costa, Marin, San Francisco, and San Mateo counties. There are about 33,000 acres of baylands in this subregion.
Historically, Central Bay supported almost equal areas of tidal flat and tidal marsh; it also had a few small lagoons and areas of muted tidal marsh. Compared to other subregions, Central Bay had relatively little tidal marsh. This reflected a combination of steep shorelines, strong currents, and wind-driven waves that prevented suspended sediments from settling out except in the quieter embayments. Figure 6.5 displays the past and present acreage of each of the key habitats in the Central Bay subregion. Today, this subregion is intensively developed; some three-quarters of its baylands are filled. Tidal marsh acreage has declined by more than 90 percent, and the area of tidal flat has decreased by 70 percent.
| Figure 6.5 Past and Present Acreages of Habitats Central Bay Subregion | |
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Adjacent Land
| South Bay Subregion | |
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The South Bay subregion includes the southern-most portion of San Francisco Bay. It abuts the Central Bay subregion on the west side at Coyote Point, and on the east side at the San Leonard Marina. An area with less rainfall than the other subregions, it has few major streams, and the larger of these include Alameda, Coyote, San Francisquito, San Mateo, and Stevens creeks. It includes lands in Alameda, Santa Clara, and San Mateo counties. Its baylands include about 75,000 acres.
Historically, the South Bay supported large expanses of tidal flat and tidal marsh. In many of the marshes between the tidal creeks were salt marsh ponds or pans. Near the mouth of San Leandro Creek on the east bay shoreline was a complex of large salt ponds referred to on historical maps as Crystal Salt Pond; this natural feature apparently was formed by beach ridge or swash bar, and it was a historical analog to the subregion's man-made salt ponds. Along much of the periphery of the baylands were wet grasslands, and a large area of wet grassland with vernal pools occurred near Warm Springs. Stands of riparian vegetation lined the watershed's many streams.
Unlike the North Bay, where the baylands were extensively diked for agriculture early on, the South Bay baylands were too saline to support much farming. Instead, they were put to another use -- salt production -- that converted large areas of tidal flat and tidal marsh to shallow ponds of varying salinities. Other development along the bayshore, including sewage treatment facilities, landfills, and residential and industrial uses, also reduced the area of natural baylands habitats.
Figure 6.6 displays the past and present acreage of each of the key habitats of the South Bay subregion. Today, this subregion is one of the most intensively developed portions of the estuary. Nearly all of the moist grasslands are gone, lost first to farming and more recently to urbanization. Likewise, much of the riparian vegetation and willow groves have been removed. Compared to historical conditions, tidal flat habitat has declined 29 percent, and tidal marsh has decreased by 84 percent.
| Figure 6.6 Past and Present Acreages of Habitats South Bay Subregion | |
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Bay
Adjacent Land
