What plants will heal the land when its future environment won't look like its past?
Climate change raises an important question for restoration ecology: What’s the best way to heal the land when its future environment won’t look like its past?
“It’s a huge issue,” said Valerie Eviner, a restoration ecology professor in the Department of Plant Sciences. “We look at our changing climate and ask, ‘What will grow? What’s even possible?’ Should we be looking at local native species or species native to areas farther south with climates more like what we anticipate?”
Restoration ecologists fight weeds, restore water flow, plant vegetation, and build healthy soil to renew land that has been damaged by human activities—like logging, mining, and development—or overrun by invasive species. They generally plant native species, which have adapted to their local environment and are usually well suited to thrive into the future.
But climate change is altering the equation.
“In many cases, seeds from local plants are no longer a match to their environment because their environment is changing so quickly,” said Truman Young, restoration ecology professor with the Department of Plant Sciences.
There are no easy answers. It’s hard to know what will survive or become invasive in an unpredictable future. Introducing species that are not locally native is highly controversial in a field focused on restoring natural ecosystems.
But a few things are certain: Restoration ecology can help mitigate climate change, in part because plants sequester carbon from the atmosphere. And UC Davis researchers are providing the science and support Californians need to protect biodiversity, manage rangeland and other working landscapes, and adapt to a changing world.
UC Davis researchers recently helped David Lewis, director of Cooperative Extension in Marin County, measure the impact of planting willows, oaks, and shrubs along 25 miles of streams in Marin County. They discovered that the plants and sediment trapped by the vegetation contain 80,000 metric tons of sequestered carbon, an amount equal to emission from 62,000 passenger cars in one year.
“That’s very big bang for the buck,” said Eviner, who co-authored the study with Toby O’Geen, Cooperative Extension soil specialist in the Department of Land, Air, and Water Resources, and Ken Tate, professor and Cooperative Extension watershed specialist
with the Department of Plant Sciences.
“Restoration benefits wildlife and water quality, and mitigates climate change,” Eviner continued. “Since we’ve destroyed about 95 percent of our wetlands and riparian areas in California, restoring these ecosystems provide a lot of potential for carbon sequestration.”
No one size fits all
With restoration ecology, everything is site specific. What flourishes in one setting may suffer next door. So ecologists already test a wide range of plant species in different locations under various conditions over many years.
“What’s different is we’re looking at what they call a ‘non-analog’ climate, where the future environment won’t look like the past,” Young explained.
No one knows for certain what the future climate will bring, but scientists predict the weather will be extreme, and evidence suggests it is already happening.
“There will be more wild swings—longer droughts and more intense flooding,” Eviner said. “So to help our ecosystems survive, we need plants that can survive the dry years and maximize water during the wet years.”
For 10 years, Eviner’s lab tested a variety of plants under manipulated conditions, simulating “normal” seasons along with drier and wetter growing seasons.
“The native, perennial grasses and native wildflowers did pretty well under those changing weather conditions,” Eviner said. “But it’s very uncertain which species have the resilience to cope with what’s to come.”
Expanding the pool
“Strategies that worked in the past are no longer working,” she said.Elise Gornish, a Cooperative Extension specialist in restoration ecology with the Department of Plant Sciences, works closely with ranchers and other private-property owners to help find the right vegetation for goals like managing weeds, reducing soil erosion, and producing forage. She finds that native species are having a hard time coping with climate change.
Gornish has begun small, controlled field tests with “non-local natives,” varieties of species that are native to nearby, hotter regions. She
is also producing a database of plants with traits like resilience to drought to analyze which plants could be good candidates for various restoration goals.
“I understand the risks of introducing non-local natives, and it needs to be studied very carefully,” Gornish said. “But to my mind, the situation is so dire we need to consider unconventional approaches to restoration.” •