Planet Garden

The chameleon, according to malagasy folklore, keeps  one eye on the past, the other  on the future. This would make it an  appropriate totem for those who practice  ecological restoration.
The past part seems straightforward enough. “Restoration” implies putting pieces back together, making something whole—a work of art, a political system, a natural community. The complications begin when you pick a baseline. In restoring California ecosystems, are we trying to recreate what was here before the Gold Rush? Before the Spanish Entrada? Drake’s landfall? Each choice has a different set of consequences.
For a long time, botanists debated whether the California sea fig was a native plant or an invasive exotic. Its nearest relatives were South African and South American, but there was no record of an accidental or intentional introduction. At the request of the state Parks and Recreation department, Susan Bicknell and Ellen Mackey examined a 900-year pollen record cored from a lakebed on the central coast. The sea fig’s  distinctive pollen appeared only in sediment deposited since 1800. Their verdict: the plant’s an alien, likely a hitchhiker in ship’s ballast.
But forget DeAnza and Drake: how about before the Holocene? It’s easy to dismiss paleontologist Paul Martin’s plea to rebuild what he has called “the last entire earth” by bringing back the elephants. Not to mention camels; other Ice Age beasts, like sabertooths and ground sloths, left no suitable next of kin. But Martin seems quite serious. And in a way, reintroducing California condors to the Grand Canyon, where none have nested for 10,000 years, is an exercise in restoring the Pleistocene.
Others have picked up the idea of “resurrection ecology,” as Robert Michael Pyle calls it. Pyle suggests translocating the nearest living relative of the extinct Xerces blue to the butterfly’s former habitat in San Francisco’s dunes. Would that be close enough, though? Would black bears from Yellowstone work as surrogate California grizzlies? (Not that bringing back an apex predator seems politically feasible; the wolf’s quiet self-reintroduction has been problematic enough.)
It may be more realistic to look for the ecological equivalents of extinct beasts. Stephen Edwards of the East Bay Regional Parks Botanic Garden argues that native California bunchgrasses co-evolved with a suite of long-gone grazing and trampling mammals: mammoths, camels, horses, bison. If so, cattle may have a positive role to play in restored grassland. It’s controversial, but Edwards makes a persuasive case.
As for the future, as long as a reservoir of weeds and other invasives exists, restorationists can’t just walk away from their work: Keeping exotics out requires a sustained commitment.
Beyond that, we all know that ecosystems aren’t static. Ponds become meadows become forests; fire, flood, and other disturbances reset the clock. Factor in anthropogenic climate change, and restoration becomes an even more complex enterprise. How do you rebuild a natural community to last?
A few years back, the Nature Conservancy funded a study of the impact of global warming on North American plants. The authors, Larry Morse and Lynn Kutner, defined a “climate envelope” for each of 15,000 native plant species, looking at mean annual temperatures. They concluded that with a global temperature increase of 3 degrees Celsius, up to 11 percent of those species would be outside their optimum climate envelopes. The percentage would be highest in the Southeastern states, but California falls in the 5 to 10 percent range.
We know something about how trees—keystone species—respond to warming climates through the work of Harvard paleoecologist Margaret Davis. Trees, like other organisms, track climate change. When the last glaciation ended 16,000 years ago, they spread north from the southern refuges where the ice had confined them. But Davis’ analysis of fossil pollen shows that they didn’t all move together like Birnam Wood. In the east, chestnuts “migrated” north at a rate of 100 meters per year, maples at 200, jack pines at 400. Some, like the Florida torreya, never made it out of their refuges at all. Davis found that lags in response to temperature change resulted in plant communities—and by extension, ecosystems—that were out of equilibrium. Such imbalances will happen again, and this time we won’t have millennia for the laggards to catch up, or unobstructed routes.
The alternatives are clear: accept the loss of whole ecosystems through global warming, or assist plant communities (and their pollinators, seed distributors, primary and secondary consumers) in their migration. The second option is a daunting but profoundly creative task: becoming, as author Connie Barlow puts it, “gardeners of the planet.”

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