An explanatory series focusing on one of the most complex issues facing California: water sharing. And at its core is the Sacramento-San Joaquin Bay Delta. Stay with kcet.org/baydelta for all the project's stories.
San Francisco Bay looked a lot different when Europeans first laid eyes on it than it does now. Aside from the lack of freeways, bridges, buildings, and landfills back then, the 18th Century Bay was also different from today's Bay in that it boasted the largest concentration of salt marshes to be found on the West Coast.
When the first western naturalists to visit San Francisco Bay arrived in 1816 aboard the Russian ship Rurik, there were an estimated 200,000 acres of salt marsh fringing the Bay's shores. By the 1990s, about 95 percent of that original salt marsh habitat had been lost.
But just what are salt marshes, and why are they important?
San Francisco Bay as we know it today got its start when rising sea levels flooded a series of coastal valleys between 8,000 and 5,000 years ago. Before the glaciers melted and sea levels rose, the Sacramento River flowed through the Golden Gate, meeting the sea after crossing a broad coastal plain that stretched for some miles past the present-day Farallon Islands. But once the polar ice caps melted, the sea rose some 400 feet, drowning that coastal plain and that series of valleys east of the Golden Gate.
It was an ecological catastrophe, but the environment adapted. Surging and receding tides, freshwater rivers' flood and drought, and centuries' worth of sediments off the still-rising Sierra Nevada built a network of tidal wetlands fringing the new Bay.
Look at a map of the Bay today and around most of its shoreline, you'll see a clear boundary between water and land. That's partly mapmakers' convenience and partly a reflection of the way we've reengineered the Bay shore. But 300 years ago, you might have found it hard to tell just where the Bay ended and the land began. The interface between land and water was ever-shifting, pulsing like the heart of California.
The Bay's wetlands can be split into a few categories. At the lowest elevations, where the soil is just too sodden and salty to support much in the way of plant life, are the mudflats. Exposed mainly at low tides, these biologically rich flats provide abundant invertebrate food for shorebirds, whose antics as they probe the muck for snacks can be pretty engaging.
Salt marshes grow a little higher than mudflats, where the soil drains just enough at low tides to provide a bit of air so that plants' roots can breathe. Three main native plant species dominated the Bay's salt marshes back in the day. Pacific cordgrass, a.k.a. Spartina foliosa, a grass that grows about five feet tall, provided most of the plant biomass in the saltmarsh. Pickleweed, Sarcocornia pacifica, a low-growing succulent shrub with jointed stems, grew either in solid stands or interspersed with open areas of cordgrass. A third species, saltgrass or Distichlis spicata, often grew in a kind of salt meadow in slightly higher elevations. All three plants are well-adapted to saline soils, secreting excess salt in amounts that can look almost like frost on their leaves.
Uphill from the saltmarsh, in areas where freshwater streams flow into the tidal wetland zone, are the freshwater and brackish marshes. The boundary between salt marsh and brackish marsh, and between brackish and freshwater, is indistinct. But in general, the fresher the water is, the more the marsh would be dominated by freshwater plants such as tules and cattails.
On higher ground without a source of fresh water, saline ephemeral pools might form, immersed during very high tides or storms, then drying out until the next flood event. Distichlis might be found fringing the pools, whether wet or dry.
Uphill even further, perhaps fifteen or twenty feet above the high tide line, riparian wetlands of willow and elder might fringe the freshwater creeks that feed the estuary. But here's the thing to remember: all these boundaries were fluid. All of them shifted. On any particular day, a cordgrass saltmarsh might be shot through with open water tidal channels, peppered with small islands of saltgrass or patches of mudflat. A good-sized storm might rearrange everything. It might wipe out an island, or drop a sandbar across a slough, keeping salt water from passing and creating a sudden freshwater marsh.
That 200,000 acres of salt marsh, part of about half a million acres of tidal wetland, was a constantly changing patchwork of different kinds of habitat. And the animals that lived there grew to depend on that patchwork of different habitats. We'll talk about two of those animals, the Ridgway's rail and the salt marsh harvest mouse, in essays to come.
Those 200,000 acres of 18th Century salt marshes didn't just go away on their own, after all. We killed them. Some, as in the North Bay, were diked off and converted to farms, growing hay for draft horses and pasture for livestock and row crops for the Bay Area's swelling cities. Some got filled in to build cities on, as towns like Berkeley and Oakland and San Francisco expanded out past the high tide line in the 19th and early 20th centuries. In the South Bay, much of the historic salt marsh was diked off and converted to salt extraction facilities. We built landfills and factories, freeways and military bases, marinas and ports and tourist towns on the old salt marshes.
Despite renewed efforts in the last 30 years to restore the bay's salt marsh habitats, rising sea levels may well undo that hard work and drown out existing salt marshes. And a blunder by early marsh restorers may turn out to be almost as destructive. Pacific cordgrass has a close cousin, Spartina alterniflora, which grows much more thickly and thus doesn't offer rails the same kind of habitat opportunities. Introduced to the Bay in the 1970s during a misguided restoration project, Spartina alterniflora outcompetes the native cordgrass, and it also hybridizes with the native startlingly effectively, which at least one researcher suggests will inevitably lead to the extinction of native cordgrass from the Bay.
As if that's not bad enough, a second invasive cordgrass species, Spartina densiflora, was brought to the Bay from Humboldt County by restorationists under the impression that it was the native cordgrass. It's actually from Chile, and escaped into Humboldt Bay after it was used as ballast in an oceangoing ship. It's also spreading throughout salt marshes in the Bay, where its habit of forming dense clumps can squeeze out both native cordgrass and pickleweed.
It's not all bad news, though. In the 1950s and 1960s, plans to fill much of what remained of San Francisco Bay angered conservationists, who began advocating on behalf of the estuary. The fruits of that activism shaped the way we view habitats such as salt marsh. What had been considered useless "swamps" were upgraded, in the public eye, to valuable "wetlands," and people started to understand the benefits such habitats offer to wildlife and people alike, from flood control to clean water to just providing homes for interesting critters.
Protecting salt marsh habitat is one thing. Restoring habitat once destroyed is another. In 1971, when San Mateo County breached a levee to allow salt water into a former East Palo Alto farmland called the "Faber Tract," a decades-long campaign to bring back the Bay as it was commenced. San Francisco Bay is now the site of what is likely the largest-scale coordinated habitat restoration effort in the world, with multiple agencies and municipalities overseeing the conversion of past wetland into once-again wetland. As I mentioned earlier in the case of the invasive cordgrasses, there have been goofs, and each individual restoration project has brought its own lessons.
Mainly, the lesson seems to be one that makes sense given how the wetlands got there in the first place: let the water come into places it once owned, then let it do the work. Planted, managed wetlands haven't fared so well. The Bay will sculpt its margins according to its own whims.
The group Save The Bay, founded in 1961 during that groundswell of public support for Bay habitats, said in a 1999 report that the Bay needs 100,000 acres of tidal marsh habitats in order for those habitats to sustain themselves into future centuries. The group points out that tidal wetlands offer immense benefits to human society such as flood control, which becomes increasingly important as sea level climbs, and carbon sequestration, which might help keep that sea level from climbing catastrophically.
And there are more intangible benefits than those, such as helping make sure kids born today still have a chaotic, inherently wild habitat to admire and explore when they grow up.