I’ve made no secret of my belief that our best bet for carbon capture and storage is to use plants. They’ve got an efficient system for pulling carbon dioxide out of the air, and they turn it into cellulose, which can be used or stored in a variety of ways. It’s not that I oppose the more high-tech solutions, just that as it stands, we very much need to be using the tools we already have.

The most popular candidate for plant-based carbon capture tends to be trees, and it’s not hard to see why. With a tree, you can really believe that it’s storing a huge amount of carbon. It’s this big, heavy, solid thing that can sometimes last for centuries. It’s also not hard to believe that something that size would have a lot of mass underground to keep it upright. The runner-up in popularity is grasslands, which store pretty much all of their carbon underground, and seem to actually be a better ecosystem for carbon capture.

Now a new contestant has entered the race. Wetlands – long understood to be vitally important ecosystems, and dangerously under-valued –  appear to be even better for carbon capture than grasslands!

DURHAM, N.C. – Human activities such as marsh draining for agriculture and logging are increasingly eating away at saltwater and freshwater wetlands that cover only 1% of Earth’s surface but store more than 20% of all the climate-warming carbon dioxide absorbed by ecosystems worldwide.

A new study published May 5 in Science by a team of Dutch, American and German scientists shows that it’s not too late to reverse the losses.

The key to success, the paper’s authors say, is using innovative restoration practices — identified in the new paper — that replicate natural landscape-building processes and enhance the restored wetlands’ carbon-storing potential.

And doing it on a large scale.

“About 1 percent of the world’s wetlands are being lost each year to pollution or marsh draining for agriculture, development and other human activities,” said Brian R. Silliman, Rachel Carson Distinguished Professor of Marine Conservation Biology at Duke University, who coauthored the study.

“Once disturbed, these wetlands release enormous amounts of CO2 from their soils, accounting for about 5 percent of global CO2 emissions annually,” Silliman said. “Hundreds, even thousands of years of stored carbon are exposed to air and start to rapidly decompose and release greenhouse gases. The result is an invisible reverse waterfall of CO2  draining into the atmosphere. The wetlands switch from being carbon sinks to sources.”

“The good news is, we now know how to restore these wetlands at a scale that was never before possible and in a way that both stops this release of carbon and re-establishes the wetland’s carbon storing capacity,” he said.

What makes most wetlands so effective at carbon storage is that they are formed and held together by plants that grow close to each other, Silliman explained. Their dense above- and below-ground mats of stems and roots trap nutrient-rich debris and defend the soil against erosion or drying out — all of which helps the plants to grow better and the soil layer to build up, locking in a lot more CO2 in the process.

In the case of raised peat bogs, the process works a little differently, Silliman noted. Layers of living peat moss on the surface act as sponges, holding enormous amounts of rainwater that sustain its own growth and keeps a much thicker layer of dead peat moss below it permanently under water. This prevents the lower layer of peat, which can measure up to 10 meters thick, from drying out, decomposing, and releasing its stored carbon back into the atmosphere. As the living mosses gradually build up, the amount of carbon stored below ground continually grows.

Successful restorations must replicate these processes, he said.

“More than half of all wetland restorations fail because the landscape-forming properties of the plants are insufficiently taken into account,” said study coauthor Tjisse van der Heide of the Royal Institute for Sea Research and the University of Groningen in the Netherlands. Planting seedlings and plugs in orderly rows equidistant from each other may seem logical, but it’s counter-productive, he said.

“Restoration is much more successful when the plants are placed in large dense clumps, when their landscape-forming properties are mimicked, or simply when very large areas are restored in one go,” van der Heide said.

“Following this guidance will allow us to restore lost wetlands at a much larger scale and increase the odds that they will thrive and continue to store carbon and perform other vital ecosystem services for years to come,” Silliman said. “The plants win, the planet wins, we all win.”

Silliman and van der Heide conducted the new study with scientists from the Netherlands’ Royal Institute for Sea Research, Utrecht University, Radboud University, the University of Groningen, the University of Florida, Duke University, and Greifswald University.

By synthesizing data on carbon capture from recent scientific studies, they found that oceans and forests hold the most CO2 globally, followed by wetlands.

“But when we looked at the amount of CO2 stored per square meter, it turned out that wetlands store about five times more CO2 than forests and as much as 500 times more than oceans,” says Ralph Temmink, a researcher at Utrecht University, who was first author on the study.

Humanity has a complicated relationship with wetlands. They’re not very compatible with how we’ve been doing things recently, and they tend to produce vast amounts of biting insects. Whether or not you think it’s a good thing, filling in wetlands in the United States is part of why cities like Boston and New York City don’t have to struggle with the burdens of endemic malaria (mass insecticide use is probably a bigger reason, especially in the south).

That said, it makes sense that marshes would do well for carbon capture, since water isn’t a limitation on photosynthesis in that kind of environment. As part of reshaping how we interact with the ecosystems around us, I think we would do very well to find a better way to live with wetlands. What’s more, much of the world has access to another “natural tool” for creating wetlands!

When I put up that beaver video the other day, I mentioned on twitter that I think we should form a cooperative relationship with beavers the way we have with dogs. I was mostly joking, but the reality is that they are phenomenal at creating wetland ecosystems, when humans don’t mess with their water supply or kill them. Simply restoring them to their historic range – especially in Eurasia – would probably pay dividends in ecosystem health and carbon capture down the road.

At the same time, we can work with sea level rise to set ourselves up for better carbon capture in the decades to come. Part of re-locating low-lying coastal communities should be de-developing those areas on our way out. Pull out as much as possible in the way of reusable materials, and pollutants, and then look into reshaping the land and planting vegetation to encourage salt marshes to grow as the water rises.

As I keep saying, we have the resources and understanding to actually deal with climate change. That doesn’t mean it’ll be easy, even if we manage to overcome the political obstacles, but the possibilities presented by everything we know are vast. The odds are not in our favor, but I believe that far from settling for bare survival, we can still make a better world.

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