By Olivia DeSmit
December 10, 2024
Upon reflection: Study gauges grasslands’ climate-fighting powers
6 min
Plant more trees, cool the climate: It’s a message that readers of this website know well.
Take southern Africa: In some places, grasses are far more effective climate allies than trees.
More or less the same principle applies with grasslands, said study co-author Heidi-Jayne Hawkins, a climate scientist at Conservation International’s affiliate in South Africa.
“There’s a lot of emphasis on planting trees to mitigate climate change,” she said, “and that makes sense for areas that were forested and should be reforested. But this seemingly simple solution of planting trees isn’t applicable for all areas. This paper shows why grasslands are so valuable by looking at another aspect of climate mitigation through cooling.”
Grasses better reflect the sun's radiation than darker, woody vegetation like trees.
The researchers also examined albedo for grasses and woody vegetation throughout the early, late and growing seasons to determine the effects of growth versus dormancy on albedo. Three different grasses — grazing lawn, red and white — were analyzed and had different albedo values.
As expected, albedo was lower for grasses during their growing season due to the green color compared to their more bleached color when dormant.
The woody vegetation and trees analyzed were perennial and do not go into dormancy, so the albedo was not as affected by changing seasons. Hawkins noted that while the woody shrubbery analyzed in this study grows year-round, deciduous trees like those in tropical savannas would likely have a bigger range in albedo due to their dormant stage and resulting leaf loss.
Taking the misguided effort of planting trees in grasslands out of the equation, even native trees may encroach. One reason for this is the loss of wild animals.
“Part of the story is that we’ve lost a lot of wild animals that used to control or remove woody vegetation — and which would have kept lands open for grasses,” Hawkins said.
Trees and woody shrubs in grasslands can contribute to the severity of wildfires as well.
“Fire is a natural part of these ecosystems, but trees planted where they shouldn’t be makes it harder to control wildfires,” Hawkins said.
Hawkins said she’s hopeful that the research will help boost understanding of grasslands as a climate ally.
“People seem to be getting the message that natural grasslands are as valuable as forests, and culturally important, not only for raising livestock but also for tourism and the wildlife that live there,” she said. “This study adds to that value.”
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