California boasts many diverse and unique inhabitants — and that includes its plants, 40 percent of which are found nowhere else in the world.
But the brewing menace of climate change threatens many species in the state’s rich flora, suggests a new analysis that models how the distribution of plants in the state may change over the next 100 years.
The bleakest end projected by climate modeling shows two-thirds of California’s flora endangered by the end of the century, the researchers report in the June 25 PLoS One.
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“It’s very sobering,” comments botanist Bruce Baldwin of the University of California, Berkeley. “This is a first approximation, but it does bracket the range of outcomes pretty well. It should prompt us to really get into gear with conservation planning. There are big challenges ahead.”
The analysis identifies safe havens — refugia where plants may congregate, such as the mountain ranges along the central coast — which would be sensible targets for conservation, says Scott Loarie, who led the research as part of his Duke University doctoral thesis.
The research highlights the importance of maintaining green spaces in developed areas, so plants can “island hop” to appropriate habitats.
Loarie, along with colleagues in California and Texas, modeled the ranges of 521 of the 2,387 plants found solely in California and a 200-kilometer surrounding region, using data on plant species and ranges from the Consortium of California Herbaria, a portal to more than 959,000 plant specimens.
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The researchers assessed changes in plant ranges over the next 100 years under several scenarios. They used two climate models — one predicting a moderate emissions increase that levels off and one predicting greater emissions that continue to grow.
They also considered two plant scenarios: one where the plants all stay put and must deal with what comes their way and one where the plants can move to greener pastures.
The general trend under all scenarios is that the bulk of plant diversity shifts north and to the coast, whether projected emissions were moderate or greater.
When plants were allowed to disperse to any adequate habitat, they needed to go an average of 150 kilometers to reach hospitable digs in the scenario projecting the highest emission increases.
Coastal redwoods, for example, may range farther north, and oaks might leave central California for the cooler KlamathMountains on the California-Oregon border. Some plants may head south, seeking the cooler, higher elevations of, for example, the Sierra Nevada.
Under the worst-case scenario, where emissions are highest and where plants do not disperse, two-thirds of the species would experience an 80 percent reduction in range size, the team reports.
But the researchers also identified several areas where large numbers of plants affected by changing climate may be able to persist. These refugia include foothills of coastal mountains, such as the SantaLuciaMountains along the central coast and the TransverseRanges between Santa Barbara and Los Angeles.
These areas are good targets for conservation efforts, Loarie says. But they are also areas under some the greatest development pressure in the country, Baldwin says.
“We have a collision between the needs of the organisms and the desire of humans to live along the coast,” Baldwin says. “There’s a real urgency to protect these critical areas from development.”
And plants that may need to live elsewhere need to get there.
“Can a little wildflower living in the foothills of the Sierras that needs to get to the coast — can it cross Sacramento?” Loarie says. Creating and maintaining islands of green and corridors among the concrete will be important in helping species persist. Some researchers are even talking of transplanting natives to these safe havens, he adds.
Of additional concern are the individual lifestyles of the plants. Even though the analysis paints a broad brush, it suggests that some species that used to live together will go their separate ways. Plants such as the Sargent cypress, which needs very specific soil types, may have more trouble migrating. And the work doesn’t look at pollinator relationships or the movement of invasive species, which could throw additional wrenches into the mix, the team writes.
The results are startling, Loarie says. “That’s not to say this will happen,” he adds. “We’re not committed to this climate change — it has everything to do with what we do in the next 100 years.”