San Francisco Bay, the Sacramento-San Joaquin Delta and the watershed that feeds them make up one of the world’s largest estuary systems, a wildly varied tableau of beaches, river, creeks, grasslands and tidal marshes. Forty
percent of the land in California drains into this rich ecosystem. 

More than 20 years ago, the San Francisco Estuary Institute, a nonprofit scientific advisory group, began an ambitious effort to guide the restoration of this landscape. But the scientists there soon ran into a huge, unanticipated question: What should the restored terrain look like, and how should its natural systems
function?

The natural ecology of the Bay Area was thoroughly demolished long ago, overrun by farms, cities and suburbs. There were few intact environments left anywhere in the region to serve as a guide. 

“There’s a 150-year gap in our memory,” said Robin Grossinger, a senior environmental scientist at the institute. To fill that gap, he and his colleagues began to scour historical records of the bay and coast for clues to how the California landscape once looked.

The institute’s historical ecology program has since evolved into one of the largest and most successful efforts to restore an ecosystem by gathering evidence on how it once was. The clues have come from a range of sources: tattered diaries and journals left by trappers and pioneers, yellowed maps made by the first Spanish explorers and survey crews, early aerial photos and narratives recorded a century ago from native people who once lived there, and even pollen deposits and tree rings.

“There’s a ton of information out there,” Erin Beller, one of the institute’s three historical ecologists, said as she reviewed maps, photos and landscape paintings at the group’s offices. “It’s scattered, but it’s out there. We trawl dozens of archives to find that transformative data.” Pay dirt might be a journal entry about a “horse that fell into the river, for example, that gives us channel depth,” she added.

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