As the verdant hills of Wakanda are secretly enriched with the fictionalmetal vibranium in “Black Panther,” your average backyard also has hidden superpowers: Its soil can absorb and store a significant amount of carbon from the air, unexpectedly making such green spaces an important asset in the battle against climate change.
Backyard soils can lock in more planet-warming carbon emissions than soils found in native grasslands or urban forests like arboretums, according to Carly Ziter, a Ph.D. candidate at the University of Wisconsin-Madison.
The results of her research, published Tuesday in the journal Ecological Applications, were something of a surprise, given that those of us who have yards generally don’t think of them as “nature,” or as especially beneficial to the environment. But at least in this case, the things we enjoy for ourselves are also helping the community at large.
Ms. Ziter studied the powers of yards by knocking on doors in Madison and asking residents to let her sample their backyard soil. Parents would often send their children outside to observe Ms. Ziter’s work. “They would say, ‘Oh, there’s a scientist in the yard, go see what she’s doing,’” she said, laughing. “All of a sudden there would be three small children and a dog surrounding me when I’m taking soil samples.”
As cities look for ways to mitigate the effects of global warming, urban green spaces are often cited as a potential solution. Green spaces can reduce temperatures in cities where paved surfaces magnify hot weather, and they can capture storm water to reduce flooding as climate change leads to increasing rainfall in some parts of the country.
Until now most research in this vein focused on larger green spaces like parks, which could give the impression that smaller spaces like yards do not contribute to the bigger urban ecosystem.
“But what we realized is that people’s backyards are a really big player here,” Ms. Ziter said.
To get a more nuanced picture of the services that green spaces provide in a city, Ms. Ziter took soil samples from 100 sites in Madison. The sites ranged from forests to grasslands to open spaces, a category that includes parks, golf courses and cemeteries. She also sampled from residential lots, which cover 47 percent of Madison’s landscape (but only parts of those lots are yards).
The study showed that the soil in forest ecosystems was best at absorbing water. But soil on open and developed land — like golf courses and backyard lawns — was better at absorbing carbon.
It was not clear why the soil in residential green spaces was better at sequestering carbon, but Ms. Ziter thinks it might be related to how people manage their yards, like by mowing. So there is a risk that the carbon we release using gas-powered lawn mowers, for example, could eclipse the soil’s ability to absorb carbon.
And before we start chopping down forests and putting in lawns, it is important to note that the study focused on soils, not on what may be growing above.
“Carbon storage as an ecosystem service can’t be just reduced to soil carbon,” said Marco Keiluweit, an assistant professor of soils and the environment at the University of Massachusetts, Amherst, who was not involved with the study. “You also have to factor in the carbon above ground. If you have a forest ecosystem you probably have as much locked up in trees.”
Still, the study suggests that fragmented ecosystems like those in backyards do benefit cities and should be factored into urban planning. For example, green spaces placed next to developed spaces might act as a buffer against the negative effects that impervious surfaces have on the environment.
Ms. Ziter and Dr. Keiluweit agreed that minimizing pavement and keeping green spaces green was an important first step.
“You don’t need to have a perfect lawn for it to be really beneficial,” Ms. Ziter said. “You don’t have to have an incredibly intensive management system. It’s O.K. to have things to be a little wild.”