WHAT COLOR IS YOUR CARBON?

continued from page 3 it to other wetlands. Gas fluxes, which Watson has also measured extensively, are another crucial piece of the puzzle. That’s because emissions of greenhouse gases from the marsh (especially methane and nitrous oxide) counteract the benefits of carbon stored in the mud.

Like I said, complicated. Since marshes typically “breathe” like this, giving off greenhouse gases at the same time they sequester carbon, researchers have to add up all the inputs and outputs to calculate the net result. “We understand why carbon is sequestered or buried in wetland soils,” says Adina Paytan of the UCSC Institute of Marine Sciences, “but it’s much harder to measure it. It’s not as easy as just measuring the diameter of a tree trunk. Here, we need these fancy towers to quantify it a bit more.”

Paytan is lead researcher on a large, collaborative project that aims to increase our understanding of total “net carbon burial” in coastal wetlands. On a cold, bright day this spring, she and a group of students and technicians from UCSC and UC Berkeley showed me one of the eddy covariance towers they’ve installed at Porter Marsh. Powered by solar panels, its instruments measure CO2, methane, water vapor, wind speed, temperature, rainfall, and more. The flux of gases between ground and air changes constantly, following cycles of plant activity from day to night, summer to winter, year to year, and place to place.

“All wetlands are different,” Paytan says. That’s why they’ve installed three such towers in wetlands around the slough with varying degrees of salinity, disturbance, pollution, and tidal influence. To help translate their results into policy action, her team—made up of scientists from five UC campuses and three national laboratories—also includes economists, social scientists, ecosystem modelers, and experts in environmental justice.

This kind of science takes time. A recent article in the journal Nature Communications with 36 authors in its byline calls blue carbon science “a vibrant field that is still far away from reaching maturity.”2

Nevertheless, researchers at Elkhorn Slough have learned a lot in fifteen years. They’ve shown that, in addition to vegetated marshes, open mudflats can also sequester substantial amounts of carbon. Yet without plants to knit the soil together, mudflat sediments are more vulnerable to erosion, making them less stable sites for long-term carbon storage. “It may take decades,” Wasson says, “but when the restored marsh plain is fully vegetated with a lush canopy, we believe that it will be a significant sink for carbon in Elkhorn Slough.”

Another takeaway from research here to date is that reducing nitrogen inputs into the slough also reduces greenhouse gas emissions. Agricultural runoff can contain dissolved nitrates from fertilizer, Watson explains, and dissolved nitrogen “fuels nitrous oxide production, a potent greenhouse gas.” This is one of many reasons ESF works not just with lands adjacent to the slough itself, but across the watershed, to support sustainable farming practices and restore ecosystem functions that mitigate water pollution.

In a warming world, we need ways not just to reduce emissions, but counteract them. Just like my teacher said in kindergarten, we should use all the crayons in the box. “It’s all important,” Paytan tells me. “Embracing renewable energy, reducing our carbon footprint, planting trees. But to limit global warming to 2 degrees Celsius and get to net zero by 2045, like the State of California wants to do, it’s not going to be enough for all of us just to drive electric cars. We need to actually suck some of the carbon dioxide from the atmosphere. Wetlands can help us do that.” n