How Do Ecosystems Adapt to Climate Change?

By Katia Savchuk

Steve Beissinger and his colleagues have been spending a lot of time outdoors. For 15 years, the conservation biology professor, who is affiliated with Berkeley’s Museum of Vertebrate Zoology, has led researchers tracking wildlife across myriad California habitats, from coastline to desert to mountain range.

The scientists are retracing the steps of Joseph Grinnell, the museum’s pioneering founding director. A century ago, Grinnell decided he would do more than just collect specimens. Traversing more than 700 sites in California, he and his students filled over 74,000 pages with descriptions of the environments they roamed, the birds they saw, and the small animals they trapped. In 1910, Grinnell predicted that the value of his pioneering field notes “will not … be realized until the lapse of many years, possibly a century.”

He was right. Grinnell’s meticulous records are now helping Beissinger and his team to better understand how California’s fauna is responding to rapid environmental shifts. It’s just one of many research projects at Berkeley that aim to shed light on how species around the world will—or won’t—adapt to climate change. The scientists involved are among more than 100 Berkeley faculty members and researchers affiliated with the cross-disciplinary Global Change Biology Initiative, founded in 2009 and funded by the Vice Chancellor for Research, the Gordon and Betty Moore Foundation, and the W. M. Keck Foundation.

In their resurveys, Beissinger and his colleagues expected to find that rising temperatures had pushed species northward and to higher elevations, where it’s cooler, but they were surprised. “We found a lot of variation, with some species moving downslope and some not changing at all, and species behaving differently in different locations,” Beissinger says. “We scratched our heads until we realized that as you move upslope, it gets cooler but also rainier. There’s a push and pull as the climate changes.”

The team also found that some birds were staying put, but breeding weeks earlier, presumably to take advantage of cooler temperatures. “It’s as if they moved, but they haven’t,” Beissinger says.

Animals aren’t the only ones moving in response to the changing climate—plants could also migrate. A 2015 study in PLOS ONE, led by David Ackerly, a professor in Berkeley’s integrative biology department, used computer modeling to predict how plants in the San Francisco Bay Area would react under more than 50 climate scenarios. The study found that as the region gets warmer and drier, shrubs and oaks will likely expand, while grasslands and coniferous forests shrink. That means chaparral could take the place of today’s redwoods.

“The time frame is really hard to nail down,” says Ackerly. “Redwoods might persist, but eventually there could be a big fire, and they don’t recover.”

The study contained a couple of surprises. First, it suggested that certain plants in the Bay Area may move downslope because it’s cooler by the ocean and rainier at higher elevations; second, that shady, moist areas could change even faster than drier ones.

Ackerly’s model predicted where plants could move to survive, not whether their seeds would actually get there. “The model shows that plants have to be able to spread quickly, and if it’s right about where conditions are going to be suitable, that’s a long way from where they are in some cases,” Ackerly explains. If barriers such as highways and agricultural fields block the way, flora could die out instead of adapting. As a result, conservationists should restore corridors that allow the free passage of plants and animals, Ackerly argues, and also consider moving some threatened species to areas likely to be more favorable to their long-term survival. For example, redwoods could be transplanted to the Oregon coast.

Anthony Barnosky, an emeritus professor of integrative biology at Berkeley, also is calling for a new approach to conservation. “The planet is changing faster and in ways it never has before,” says Barnosky. “So the question in conservation really becomes: How do you maximize ecosystems’ ability to cope with change?”

As lead author of a paper in Science in February, Barnosky, along with Ackerly and a handful of other Berkeley scientists, contends that conservationists need to go beyond trying to preserve America’s natural landscapes. That doesn’t work, they say, because the climate is changing too fast for many species to adapt, and because too little of that traditional habitat remains; more than half of the planet consists of manmade ecosystems such as farms and pastures.

The Science paper urges conservationists instead to use paleontology to illuminate long-term trends. “We can use the fossil record to see whether climate changes we’re seeing [in a region] are more extensive than any in the past and come up with predictions about how species are going to respond, and anticipate what needs to get done,” explains Barnosky. “Is it going to be worthwhile to keep species in a certain place, or should we let them disappear and see what moves in, or should we acquire new lands nearby that would allow them to survive?”

Fossil records can help answer those questions, he argues, by clarifying how much human influence has disturbed an ecosystem over centuries. “We have to start thinking about how we can use this mosaic of novel and historical ecosystems to help species rearrange in a way that’s going to keep them on the planet,” Barnosky says.

Instead of dying out or migrating, some species may evolve. A study published in March in Science, involving several Berkeley scientists, showed that shifts in precipitation could influence natural selection. Analyzing nearly 170 studies of plants and animals around the world, the researchers showed that rainfall explained 20 to 40 percent of variation in natural selection. Surprisingly, temperature had little effect (though researchers say this could be partly due to their focus on annual averages).

Study coauthor Stephanie Carlson, an associate professor in Berkeley’s environmental science, policy, and management department, says it’s already well established that precipitation levels affect selection. Add in that “We know from climate models that patterns of precipitation are likely to change.” The bottom line of all this: “We show that it’s possible for populations to evolve adaptively in response to climate change.”

Carlson stresses that the research does not show whether species actually are evolving in response to climatic shifts, which would require tracking adaptive traits across many generations. It is also unclear whether species could adapt quickly enough.

“Our study gives a little glimmer of hope that organisms could adapt, but that will only happen if the rate of evolutionary change can keep pace with the rate of climate change, which is unprecedented,” Carlson says. “I don’t think we could count on evolution to save populations in distress.” 

Katia Savchuk is a regular contributor to California.

From the Summer 2017 Adaptation issue of California.
Filed under: Science + Health
Image source: Paul Reaves Photography, Thinkstock
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