The Bay has survived through millennia, but can it adapt to sea-level rise? Well, that depends on whether tech companies will step up. The San Francisco Bay is not what it used to be; the region and the Bay itself have changed enormously through the centuries. We chatted with Matthew Booker — a historian at North Carolina State University who literally wrote the book on its ecological and environmental history (Down by the Bay: San Francisco’s History Between the Tides) — about how the ecosystem of the Bay has evolved from ancient times through current-day climate change.
Prehistoric, the Last Glacial Maximum. 20,000 years ago, when most of the world’s water was tied up in giant ice sheets that covered huge swaths of the landscape, the Bay did not exist. In fact, the continental shelf — the area where exposed land met the sea — was located all the way out by the Farallon Islands. “The glaciers sucked up an enormous volume of water, so much so that it dropped the world’s coastline by dozens upon dozens of feet,” says Booker.
Pleistocene and Later. As the last ice age ended and the massive glaciers started to melt, sea levels around the world began to rise and the ecosystem of the Bay changed drastically. About 8,000 to 5,000 years ago, the glaciers had melted enough that water pushed through the Golden Gate and started to fill the Bay. “There are giant camels, huge ground sloths, mammoths and giant beavers,” Booker explains, setting the scene. “All the creatures lived down there on what is now the Bay floor. As the ocean comes in and creates the Bay, it also creates an estuary from a river valley — the mixing areas from big rivers that were much bigger then because they’re carrying glacial melt — so it probably looks like those big white foaming rivers you see today in Alaska.”
Native Americans. Though Native Americans had been in the area since the end of the ice age, by an estimated 2,000 years ago, their numbers grew dramatically. As the glaciers continued to melt, the Bay was now filled in to a size even larger than it is today. Native Americans were hunting and eating the giant animals that lived in the area, especially shellfish off the coast — oysters and clams that grew on rocks —and creating huge piles of discarded shells. Called shellmounds, these construction projects remade the landscape and eventually numbered about 400 to 500.
1770s. The Native population of theBay Area numbered about 100,000 people. When the Spanish arrived, they brought grazing animals and agriculture along, which ended the building of shellmounds and replaced them with an ecosystem of farmland. The animals, which hung out in small spaces and ate all the grass and brush, caused enormous mudslides throughout the region.“It makes the Bay smaller, the land bigger, and it increases the marsh area,” says Booker.
1840s: The Age of Fill. The city of San Francisco was created in the course of a few months as goldminers rush in. The population ballooned from about 750 people to 50,000. When Americans arrived in San Francisco, their main goal (other than gold) was making money from buying and selling private property. So they started filling in large areas of the Bay to increase the landmass available for purchase and sale around the City. “Americans invent a new kind of land, which is just a fantasy — you can buy and sell it without doing anything with it. It’s not the land itself,” notes Booker, “it’s the promise of what it represents.” That made the earliest days of San Francisco not all that different from the much-coveted metropolis it is today. “They’re really into flipping,” he says of 21st-century entrepreneurs. “Much as history is about change, this is an example of continuity. San Francisco was the real estate capital.
1850s: Gold Rush. The Gold Rush itself didn’t happen in the Bay Area; rather, it happened up in the Sierras. Small miners moved out, and large corporations moved in and built massive hydraulic water systems to wash gold, taking control of many of the rivers and streams in the area. “They liberate huge amounts of soil,” Booker says. “So much dirt and soil and gravel and sand gets moved that they fill in the rivers up to 50 feet in some places and all that stuff slowly migrates downstream — that just finished peaking a few years ago.” All told, their tailings fill in the Bay by as much as a meter. “[Human activity] speeds up the geological processes that created the Bay by thousands of years in the amount of about 40 years.” By the end of the Age of Fill, the Bay is 30 percent smaller and its edges, which used to be gradual, are now a sharp drop-off.
1950s: Save the Bay. The Bay itself was getting smaller and smaller as people built out into it more. There were few recreational areas and almost no beaches. The Army Corps of Engineers created a plan to fill in most of what was left of the Bay and put dams in where many of the bridges are now, creating large lakes. This triggered a famous backlash and community coalition called Save The Bay that catapulted the area into an environmental age of conservation. Filling was banned around the Bay and parks and public lands popped up around the area.
Modern Time and the Future of Sea-Level Rise. Looking forward, the future of the Bay ecosystem won’t just be conservation but also adaptation and restoration. As climate change forces sea-level rise to speed up, it will be essential to bring back the area’s old marshlands to absorb water and prevent flooding. “I’m really concerned about the tech companies. They’re all on fill. Google has shellmound on their property. The tech companies need to get on board. The great hope is that they would get together and they could make a great project of the 21st century adapting to sea-level rise. They have a personal stake,” Booker says.