Trapped Underground


Human development and fires are damaging and destroying the globe's natural habitats, but its plant life may be most helpful in healing the earth's carbon-choked atmosphere. During photosynthesis, plants take in carbon dioxide (CO2) from the air and store it underground—effectively removing carbon from the atmosphere.

Patty Oikawa, Ph.D., assistant professor of earth and environmental studies at California State University, East Bay, is studying a habitat that is particularly effective at this carbon sequestration process: wetlands.

“In most ecosystems, that biomass stays there for a little while but then it decomposes; it just breaks down and turns back into CO2 and goes back into the atmosphere," Dr. Oikawa says. “But in wetlands, they're unique in the sense that they're flooded, and the water makes the soils anoxic—so there's no oxygen in the soils. … Whenever that plant biomass dies, it tends not to break down. It just stays there. And the carbon then builds up over time, and you can get carbon stored there for thousands of years."

Professor Patty Oikawa works with students on the Eddy Covariance Flux Tower, 2018.

Professor Patty Oikawa, left, works with students on the Eddy Covariance Flux Tower, 2018.

Focusing on the Eden Landing Ecological Reserve on the San Francisco Bay—one of the country's largest wetlands restoration projects—Oikawa is quantifying the amount of carbon sequestered by these wetlands using an Eddy Covariance Flux Tower, which measures the amount of carbon in the air. But she's also testing the amount of carbon being exchanged between the wetland and the ocean in the tides.

“We can see how much carbon the wetland is extracting from the atmosphere and where it's going," she says. “Is it staying there, is it in the soil or is it being transported out into the bay? Then we can also measure our soils, go back in time and look at how much soil is being stored and built up over time, and relate that with sea level rise."

The research is particularly helpful for industries participating in California's Cap-and-Trade Program—which sets a maximum on greenhouse gas emissions, but allows companies to counteract their emissions by investing in projects that reduce carbon, fundamentally creating a “carbon market." Oikawa's team developed protocols for the San Francisco Bay Delta and Sacramento-San Joaquin River Delta, currently being considered by the California Air Resources Board, for how industries can invest in these wetlands to make this exchange.

“This is providing an avenue for some people to build wetlands that wouldn't otherwise be restored or built, and they can help finance that restoration through these carbon markets," Oikawa explains.

In addition, she is studying ways to increase carbon sequestration in California's range and grasslands. At several sites throughout the state, her team has applied a quarter inch of compost made from excess waste like food and manure to lands where ranchers graze their cattle. Already, the compost has helped the plants grow bigger and greener and is allowing them to store more carbon underground.

A tractor spreads compost across rangelands.

A tractor spreads compost across rangelands.

“Wetlands store a lot more carbon and are really good at it, but they encompass a small fraction of the land surface," she says. “So even though we're talking about a lot smaller carbon sequestration on range lands, they cover 40 percent of the land surface and actually have a bigger potential impact. Plus, you have the added benefit of reusing some of our waste streams, which is a problem anyway from a greenhouse gas perspective."

Ultimately, the aim is to find more ways to meet the state, country and global carbon emission goals. “We need to figure out what our options are for this active removal from the atmosphere," Oikawa says. “There's not just going to be one negative emission technology. Every location, every nation is going to have to address this with their own ideas."