Researchers at Colorado State University are leading an attempt to restore Yosemite National Park’s iconic meadows before it’s too late by reintroducing native plants that once covered the landscape.
Overgrazing of Yosemite’s Tuolumne Meadows by sheep in the 19th century depleted native wet meadow plants and degraded soil quality, endangering a key ecosystem for Yosemite’s wildlife and threatening mountain views treasured by park visitors. Without deep-rooted vegetation to maintain soil health and moisture, the meadows are releasing carbon, and recovery becomes less likely as the soil loses water-holding capacity and dries out.
To prevent continued ecosystem decline, scientists planted 40,000 native sedge seedlings in the meadows and monitored recovery. After three years, they found the sedges were slowly improving soil health by increasing soil organic matter, but the meadow was still losing carbon overall through continued decomposition of soil organic matter. These results indicate that recovery will be slow, but restoring a plant that historically dominated the landscape will help prevent further ecosystem decline.
"Many ecosystems do not naturally recover from severe disturbance, and while a place may look green, it may be severely degraded and in need of restoration,” said lead author David Cooper, a senior research scientist emeritus in CSU’s Department of Forest and Rangeland Stewardship. “We feel our approach of planting the species that was and should be the dominant vegetation is the path forward.”
Cooper added that it might take 25-50 years to repair damage that has been ongoing over the past roughly 150 years.
“I think the meadow can be restored, but these things take time,” he said.
From the mid-1800s until years after the national park was established in 1890, primarily sheep raised as livestock grazed deep-rooted, carbon-fixing sedges to the point that they have not rebounded on their own more than a century after grazing ended. Shallow-rooted plants replaced the native sedges, and soil left bare or without biomass from deeper-rooted plants dried out. More than 20% of the meadows’ topsoil remains exposed.
Results are published in the Journal of Geophysical Research: Biogeosciences .
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