Biodiversity-friendly grasslands take longer to restore than previously thought

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New research from the University of Colorado at Boulder shows that often-neglected grasslands take centuries to rebuild their resilience after disturbances such as fires or urban development.

Grasslands make up nearly 40% of terrestrial ecosystems, provide habitats for a wide diversity of animals and plants, and contribute to the livelihoods of more than a billion people around the world, according to the study published in the journal Science August 5.

For years, researchers assumed that the ecological development of grasslands was a rapid process; however, the recovery is not as fast as they once thought. The new study found that the resilience of grasslands to disturbances, including fire, heat and drought, is the result of centuries-old processes.

Grasslands are often used for agricultural land or city development, a process that is usually irreversible. Grassland recovery happens slowly or not at all, and it takes hundreds of years for grassland resilience to be restored.

“Recovering grasslands don’t have the same species or characteristics as before tillage or tree planting, and they take centuries to re-grow,” said Katharine Suding, lead author of the article and distinguished professor in the Department of Ecology and Ecology. Evolutionary Biology and Institute of Arctic and Alpine Research at CU Boulder.

“Grassland restoration must be viewed through an old-growth lens,” Suding said. “Yes, there are ancient grasslands. You can find them all over the world. Like old-growth forests, these ancient grasslands have unique characteristics that take centuries to develop.

Suding has worked with other experts to assess current grassland conservation and research. Much of the complex grassland structure is found underground, so it’s often overlooked and difficult to study, Suding said.

They found that the previous hands-off approach to grassland restoration was not working. Grasslands must be restored in a step-by-step process.

To help grasslands recover, Suding said conservationists and researchers need to be patient. “Grasslands can stay forever young if we treat restoration as a one-time event and then move away from it,” she said.

“These species depend on underground regrowth and clonal propagation for their persistence. We cannot ignore these bud, slow-growing, seedless species in the restoration,” Suding added. “Management must also change over time based on how recovering vegetation affects fire, grazing and soil, and how they in turn affect vegetation.”

Arid grasslands, grasslands and coastal grasslands, through to those in the tropics and savannahs, need time to develop and change as species become established and soil develops. In the meantime, the old grasslands that are still intact must be preserved.

Planting trees has been a solution in the past, but planting trees on grasslands could destroy more than it creates, according to the UN Decade of Ecosystem Restoration initiative. Researchers must now determine where and which grasslands to restore.

“While there are many challenges ahead, taking a long-term view of assembling grasslands toward old-growth characteristics, with unique biota and below-ground complexity, will allow us to achieve ambitious goals of restoration of Earth’s grassy ecosystems,” Suding said. “We cannot ignore them in our global restoration efforts.”

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