AT FIRST GLANCE, you would probably mistake the place for a vacant lot in the
semi-industrial landscape of southern San Francisco Bay. To the west lie giant
industrial salt ponds; to the east, a profusion of freeways, power lines and
hastily built Internet office parks. Until recently, most conservationists would
have dismissed it as not worth their attention. Yet this patch of
earth鈥攐nce a horse pasture, before that a beet field鈥攊s one of the
most precious ecological jewels in the Bay Area. It is a remnant of the
seasonal, or vernal, pools that dotted the area before Europeans arrived.
This hidden treasure was recognised for what it is thanks to some extremely
careful historical sleuthing by the San Francisco Estuary Institute (SFEI), a
nonprofit environmental research centre in Richmond, just across the bay from
San Francisco. SFEI is a leader in the worldwide trend toward deeper, more
thorough use of historical sources in habitat restoration. By piecing together
old maps, settlers鈥� journals and other historical sources often ignored by
ecologists in the past, researchers at the institute mapped what the Bay Area
looked like when Europeans arrived about 200 years ago.
What they found suggests that the region鈥檚 true ecological past looked a lot
different from what people thought, and this in turn has changed what
conservationists aim for in restoring native habitat. The maps also reveal that
bits of the past still survive tucked in amid a seemingly random jumble of
housing tracts, parking lots, warehouses and neglected fields.
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Among these surprising survivors are the vernal pools. Most ecologists had
thought the ponds found in the Bay Area today were not true vernal pools because
such pools had never existed in the area. Yet according to SFEI鈥檚 maps they once
occupied a broad strip running along what is now Interstate 880 between the
cities of Fremont and Hayward. 鈥淥nce you see it on a map, you understand why
those pools are there,鈥� says Carl Wilcox, a regional conservation planning
manager with the California Department of Fish and Game. 鈥淚f we hadn鈥檛 had that
historical picture, people wouldn鈥檛 have realised what a unique remnant it
颈蝉.鈥�
All attempts at restoration have to begin with at least a rudimentary notion
of what the landscape once looked like, but few previous efforts can match the
detailed, comprehensive view of an ecosystem鈥檚 history provided by SFEI鈥檚 maps.
Part of a compilation called the Bay Area EcoAtlas, they illustrate features as
small as 100 square metres, across a region encompassing almost 4000 square
kilometres. The maps were produced for SFEI鈥檚 Historical Ecology Project,
initiated in 1993 by wetlands scientist Josh Collins to help guide
conservationists in restoring the estuary. 鈥淛osh鈥檚 insight was that there was a
lot of mythology out there about how things used to be,鈥� says Robin Grossinger,
another SFEI scientist. 鈥淭here were always a couple of old documents used in
restoration planning, but they got overinterpreted. The story changes if you go
through a lot of historical sources.鈥�
Army of volunteers
Information from over 1000 documents has gone into the maps. These sources
include 18th and 19th-century maps, paintings, photographs, pamphlets on local
history, interviews with elderly residents, and journals of explorers, settlers
and early naturalists. It took Grossinger, other scientists and an army of
volunteers more than two years of research to assemble the sources. 鈥淩esources
were scattered throughout the community, in historical societies, attics and
people鈥檚 memories,鈥� Grossinger says. Previous workers had neglected historical
documents, in part because of their uncertain accuracy. But SFEI cast a
scientific eye on these records, and developed a system for scoring the
likelihood鈥攑ossible, probable or definite鈥攐f the presence, size and
location of each feature of the landscape.
To make the maps, Grossinger and Elise Brewster, an artist and collaborator
on the project, assembled layer upon layer of information from this profusion of
sources. As Brewster drew the final copies of the maps, Grossinger sat beside
her, annotating the sources and certainty of each line.
The basic history of the Bay Area is well known. When Spanish explorers
sighted San Francisco Bay in 1769 it was an unbroken expanse of mudflats and
marsh inundated twice daily by the tides鈥攐ne of the largest estuaries in
the world. Since then it has become a sprawling metropolis, home to 7 million
people. But what exactly did those original marshes look like? The fragments
that remain are relatively flat, homogenous plains lush with cordgrass and
pickleweed, and well drained by tidal creeks that leave little standing water.
Most experts assumed that鈥檚 what the original marshes looked like too.
Restoring such marshes would benefit some of the Bay Area鈥檚 nearly two dozen
threatened and endangered species, such as the salt marsh harvest mouse and
birds like the California clapper rail. 快猫短视频s also know that when Europeans
started to settle the estuary it supported huge waterfowl populations: early
settlers wrote that the sky darkened with ducks at a single rifle crack. Today,
ducks and other waterfowl still inhabit the bay鈥檚 drained marshes and industrial
salt ponds. But if the marsh were returned to what was believed to be its
original state, these habitats would be eliminated. So where exactly had these
enormous flocks lived in the past?
SFEI鈥檚 analysis yielded a totally different view of the marshes鈥攁 view
that resolved some of these apparent conflicts. A series of maps made by the US
Coast Survey in the 1850s and 60s showed the tidal marsh as a mosaic of
interconnected habitats. Some areas did have numerous creeks and channels, while
others were poorly drained and contained seasonal and permanent ponds of diverse
shapes, sizes and salinities. Maps and records made by private hunting clubs
identified some of these marsh ponds as key hunting grounds鈥攊n other
words, excellent habitat for the huge flocks of ducks.
Moreover, herbarium records and the notebooks and journals of early
naturalists showed that in some parts of the bay the landward edges of the early
marshes were not generally steep, as they are today, but rather a gradual slope
along which marsh vegetation gave way to a broad swath of transitional plants
and then upland grasses. This transitional zone, which is not found in modern
marshes, contained entire plant communities not found today, with more species
than the marsh proper. 鈥淭he EcoAtlas helped us understand that a natural marsh
is not a sea of pickleweed. There鈥檚 lots of habitat diversity within it,鈥� says
Wilcox.
Other historical sources revealed an array of forgotten habitats that
disappeared soon after Europeans settled. 鈥淚n the 1870s to 1890s, people were
already talking about how much had been lost,鈥� says Grossinger. 鈥淥ne hundred
years later we have a very simplified view of the ecosystem.鈥� The Coast Survey
maps, for example, showed sandy beach ridges, both within the tidal marsh and
adjacent to it, that would have supported rare plants such as California
saltbush and northern salt marsh bird鈥檚 beak, as well as shorebirds such as the
endangered snowy plover. Spanish written accounts made frequent reference to
鈥渟ausals鈥� or willow groves, which probably provided habitat for songbirds and
amphibians.
Now that ecologists know what to look for, they are finding unexpected bits
of the past all over the urban landscape. 鈥淭here are many habitats that are
talked about now that previously weren鈥檛 on anybody鈥檚 radar screen,鈥� says
Grossinger. 鈥淭here鈥檚 actually a lot more left than you would think.鈥� Once, these
fragments would have seemed random. Now they look like opportunities.
In the early 1990s, when biologists began noticing vernal pool plants in
pastures at the southern end of the Bay, they initially classified them as
鈥渆rratic鈥濃�攁n ecological accident. A few years later, when real estate
developers wanted to build an office park on a nearby 300-hectare parcel of old
horse pasture in Fremont, biological surveys again turned up vernal pool plants.
By then, SFEI had a rough draft of the EcoAtlas maps, as well as information
from a 1913 soil survey that suggested these areas included old vernal pools.
After a lengthy regulatory battle, the developers were allowed to build on only
150 hectares, and agreed to restore the vernal pools on the other half of the
parcel.
A wilderness of tollbooths
Even in newly formed habitats, careful historical reconstruction can point to
similar, long-vanished equivalents in the past. Over the past few years, for
example, a series of beach ridges has grown up beside the eastern approach to
the San Francisco-Oakland Bay Bridge, an area that to the untrained eye looks
like a wilderness of tollbooths, asphalt and steel bridge pilings, with distant
views of the downtown San Francisco skyline. SFEI鈥檚 maps show that similar
ridges once occurred at other locations in the bay with similar tides, currents
and topography.
That link helped Peter Baye, a botanist with the US Fish and Wildlife
Service, decide that the coarse, well-drained sand of the ridge tops would be a
perfect habitat for California sea-blite. This obscure plant is now extinct in
San Francisco Bay, but Baye hopes to reintroduce it beside the bridge and in
half a dozen other sites around the bay where beach ridges might support it.
Though he might quibble with a few details of SFEI鈥檚 reconstruction, Baye says
it has changed his vision of what species belong where in the bay. 鈥淎nd that鈥檚
the holy grail of restoration鈥攖o know what habitats and species
assemblages belong where, and what processes contribute to producing them,鈥� he
says.
This changing vision of the value of history in ecological restoration is
spreading well beyond the Bay Area. Similar efforts are under way for the rivers
of the Seattle area, Chesapeake Bay, the Grand Canyon and other environments
worldwide. In Britain, Ian Rotherham and his colleagues at Sheffield Hallam
University are digging into the history of Britain鈥檚 wetlands, woodlands and
heaths. At Wharncliffe Heath and Crags near Sheffield, they have found that the
heathland now preserved in this urban refuge probably formed after Roman workers
destroyed the area鈥檚 original soil as they quarried the quernstones used for
grinding grain. 鈥淭he landscape we see today is a complex overlaying of
historical and ecological factors,鈥� says Rotherham.
This human role in creating habitat will be SFEI鈥檚 next focus. 鈥淓very plant
and animal community in the Bay Area has interacted with human beings for
thousands of years,鈥� says Chuck Striplen, a Native American ecologist of the
Ohlone tribe who is collaborating with SFEI to rediscover native land management
practices.
Meanwhile, SFEI鈥檚 maps have formed the basis for a comprehensive set of
restoration goals in the Bay Area, and are influencing a variety of government
and private restoration projects. The US Fish and Wildlife Service, for example,
is now incorporating transitional zones into the marshes they restore, says
Wilcox. Restorationists are also scooping out ponds at the back of newly created
marshes to provide waterfowl habitat.
Thanks to SFEI and its careful study of history, the past is re-emerging
around the bay, side by side with the 21st century and within sight of San
Francisco鈥檚 gleaming skyline. As Grossinger says, 鈥淭he historical landscape is
not as far away as it seems.鈥�