Sometime in our recent past, we became obsessed with planting trees. First, the goal was 1 billion new trees worldwide. Now it’s 1 trillion by the year 2030.
Trees offer all kinds of benefits, from absorbing climate-warming emissions to providing refuge for animals, and we’re losing them at a blistering pace. But in our push to restock the world’s forests, we’ve largely ignored — and in some cases harmed — another important ecosystem that offers a similar set of benefits: grasslands.
Covering about 40 percent of the Earth, grasslands are sometimes considered little more than blank wastelands — but they’re anything but barren. Grasslands harbor a diversity of species that rivals forests, and their deep root systems store carbon that won’t go up in smoke during a wildfire.
“As we’re seeing increasing drought and increasing fire, we’re likely to rely on grasslands more because they’re a more resilient carbon sink,” said Elizabeth Borer, a grassland expert at the University of Minnesota.
Yet nearly half of the world’s grasslands are now degraded. And unlike forests, they have drawn little attention even within the conservation community, according to a recent article in Nature. That’s why experts are calling for a reimagining of which ecosystems are important — and urging people to look beyond forests to humble blades of grass.
Don’t confuse grasslands with grass
By “grasslands,” I do not mean lawns. Most lawns are resource-intensive monocultures of invasive plants. Each year, Americans douse their lawns and gardens with almost 3 trillion gallons of water and, as of 2012, 59 million pounds of pesticides. That’s to say nothing of the carbon pumped into the air by lawn equipment. All those inputs provide very little in return other than a bright patch of green. Manicured lawns are the real wastelands.
The tallgrass prairie of the Great Plains or the tropical savanna in the Cerrado of Brazil, by contrast, are natural grasslands full of life. In just a quarter of an acre in the Cerrado, for example, scientists have recorded 230 species of plants. Those plants in turn feed countless animals, from the critically endangered blue-eyed ground-dove to the lanky maned wolf. Research has found that natural grasslands — loosely defined as open ecosystems with low-lying vegetation and few trees — harbor a similar number of vertebrate species, like birds and mammals, as forests.
Unlike lawns, grasslands are also superstars of ecosystem services, which describe the ways that landscapes benefit human society. Natural grasses have enormous root systems — often far larger than the plant you see above ground — which hold the soil together and help prevent erosion. Research suggests grasslands also hold more than a third of the world’s land-based carbon. “You don’t see the carbon that grassland plants are pumping below ground, but they’re storing enormous amounts of it,” Borer said.
Most of that carbon is protected from wildfires, which typically just burn through above-ground vegetation, she said. In fact, fires can actually promote the growth of grasslands and even help them store carbon more efficiently, said John Blair, a professor of ecology at Kansas State University. In forests, severe wildfires release large quantities of carbon into the air, and it can take decades for the trees to recover.
Nearly half of all grasslands are degraded
As much as 49 percent of grasslands, worldwide, are degraded to some extent. And in the tropics, the Earth is losing these ecosystems faster than it’s losing forests — which, as you might guess, is really fast.
Alarmingly, some grasslands are nearly gone already. More than 94 percent of North America’s tallgrass prairie has been wiped out, for example, while we’ve lost more than half of the Brazilian Cerrado in the last 50 years — “exceeding the rate of forest loss in the Brazilian Amazon,” authors of one study wrote.
As you’d expect, populations of animals that depend on these systems are dwindling, too. In North America, grassland birds, such as meadowlarks and grasshopper sparrows, “are declining all over the place,” Blair said. “They just may be a harbinger of the greater biodiversity loss we’ll see in the future.”
The most obvious culprit behind the degradation of grasslands is farming and ranching. Grassland soil is full of nutrients, after all, and it’s much easier to convert into a farm or pasture than, say, a forest. Between 2008 and 2016, the US converted more than a million acres of grasslands and other ecosystems into cropland each year, according to one 2020 study. It came at a great cost to wildlife, the authors wrote. During that period, the Midwest alone lost an estimated 220 million milkweed plants, which is one of the only food sources for the monarch caterpillar. (Populations of eastern monarch butterflies have fallen by more than 80 percent in the last two decades.)
The poor reputation of grasslands has only made the problem worse — and left these ecosystems largely undefended. “Natural grasslands are often erroneously considered to be degraded lands,” the authors of the Nature article wrote. As a result, these ecosystems have been overlooked in some major international efforts to curb biodiversity loss, they wrote.
While stopping the destruction of ecosystems is a “central goal” of major international treaties including the UN Framework Convention on Climate Change (which includes the Paris Agreement) and the Convention on Biological Diversity, “there is no explicit mention of grasslands in any of them,” the authors wrote.
“There’s lots and lots of emphasis on forests but there’s very little emphasis on grasslands,” said Richard Bardgett, the article’s lead author and a professor of ecology at the UK’s University of Manchester.
Planting trees sometimes comes at the expense of grasslands
In some cases, efforts to restore forests harm grasslands. If you view grasslands as degraded forests, you might decide to seed them with trees instead, especially if you’re trying to hit lofty tree-planting targets.
Over the past 25 years, China — which has invested massively in tree planting through its Grain to Green initiative — increased the coverage of trees in areas that were not traditionally forested by an average of more than 370,000 acres per year. “Similarly, large tracts of natural grassland in Brazil have been identified as targets for tree planting, posing a major threat to these ancient and highly diverse ecosystems,” authors of the Nature perspective wrote.
Tree-planting programs are designed in part to reduce carbon dioxide emissions and slow climate change. But planting in grasslands can work directly against that goal, Bardgett says. “Tree roots can penetrate into the soil and can actually degrade organic matter and lead to the breakdown and release of carbon from the soil,” he said. Trees also require more water than grasses and can sap the ground of moisture and shrink nearby streams.
That’s one reason why some scientists are skeptical about mass tree-planting efforts. “It’s a great concept and has brought some clear attention to ecosystem services provided by our landscape, but its narrowness is problematic for true conservation,” Borer said.
What if humans treated grass like they treat trees?
The first step to saving grasslands is to expand our definition of natural, carbon-rich ecosystems beyond just forests, experts say. “We need to shift people’s perception of how diverse and complex grassland ecosystems are,” Blair said.
The next priority should be protecting the small number of grasslands that are still unharmed, Bardgett said. Currently, protected areas cover only about 8 percent of grasslands and savannas, according to his paper, compared with roughly 18 percent of forests.
Restoration also poses a big opportunity, said Diane Debinski, a professor of conservation biology at Montana State University who’s studied grasslands for more than two decades. Even restoring grasslands on the side of the road, at the edge of a farm, or along a small stream can offer major benefits, such as preventing erosion and flooding, she said.
The US government could fuel some of those efforts. Earlier this year, President Joe Biden announced plans to conserve at least 30 percent of American land by 2030, which will include working lands like farms and ranches. His administration already expanded its Conservation Reserve Program, as part of the 30-by-30 push, which pays farmers to plant beneficial species and take environmentally sensitive land out of production.
But restoration is far from perfect. One challenge, Debinski said, is funding. Seeds of a Great Plains flower called the prairie violet, for example, are pricey, so scientists often don’t plant them, even though they’re one of the few host plants for the regal fritillary butterfly, a vulnerable species.
We also rely on grasslands for much of our food, so “it’s not realistic to say we just need to restore all of the grasslands,” Borer said. “We need an integrated approach,” she said. In other words, we should consider the whole suite of benefits that grasslands provide, from land for grazing to habitat for threatened species, when thinking about restoration. “The key thing is understanding what the tradeoffs are,” Bardgett said.
There’s another, easier solution: Rip up your lawn and replace it with native plants. Across the US, there are as many as 50 million acres of lawn — an area roughly the size of Nebraska. Restoring even a small portion of that area would be a major boon for wildlife and the climate. “If you have a fraction of an acre, you can make part of that into habitat that’s valuable for insects and for songbirds,” said Debinski. “Restoration and conservation can be done at a fractional level.”
vox.com, 10 September 2021