Climate Roulette

How will America’s biodiversity hotspot — the state of California — fare as the climate changes? Not great, according to a new paper in the peer-reviewed online journal PLoS One. Its findings have implications for plant conservation that are guaranteed to raise a few eyebrows. 

The paper was the buzz among botanists at the annual conference of the American Public Garden Association in Pasadena a couple of weeks ago. California’s diverse and distinctive flora faces a potential “collapse,” David Ackerly, an ecologist at UC Berkeley and the senior author of the paper, told the LA Times. “As the climate changes, many of these plants will have no place to go.” 

California has roughly a quarter of all native plant species in the U.S. Forty percent of the state’s native plants, or 2,387 species, are found nowhere else in the world, from the towering coast redwoods to the tiny Laguna Beach dudleya. Under the worst-case scenario examined in the paper, 66 percent of all species unique to California would suffer more than an 80 percent decrease in range. 

In a hundred years, the Golden State could look a lot different than it does today. Because California has such varied terrain, climate change could cause species to move in different directions. Most plants, including the redwoods, will be forced to shift northwards and towards the coast. But in the Cascade Ranges and the Sierra Nevada, species seeking higher elevations will have to move south. Plants of Northern Baja will migrate into San Diego County, while the Central Valley could become the preferred habitat for plants of the Sonoran Desert. And what about Orange County and LA? According to another one of the authors quoted in the Times, they could become a land of “desert plants similar to those in Nevada and Arizona, but more likely unpleasant agricultural weeds.” And this all assumes the plants will be able to migrate — no easy task, given that many will have to leapfrog the endless housing subdivisions, freeways, and other development that have tattered their habitats.

The authors advocate measures that would make plant conservation, already a difficult undertaking, even more complicated. For example, they favor efforts to preserve areas where species at risk from climate change are most likely to persist in the future. Most controversial of all, they suggest that “species dispersal” — also known as assisted migration, in which humans move other species to cooler places — will be essential to maintain biodiversity. 

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