How Compost Captures Carbon and Helps Heal Rangelands and Wetlands

Carbon Capture Carbon Emissions Greenhouse Gases Compost Restoration Wetlands Rangelands California
Marin rangeland and wetland, Inverness, CA. credit: Philippe Vieux-Jeanton

Scientists are in agreement: Global warming is the result of human-caused emission of greenhouse gases, with carbon dioxide as the biggest contributor. We all know that burning fossil fuels is the major source of human-produced carbon dioxide emissions; however oceans, land and vegetation all emit carbon. Carbon has been increasing in the atmosphere since the industrial revolution, largely due to the burning of fossil fuels, but also due to changes in land use.

Due to the demands of population growth, much of California’s rangelands (vast landscapes that grow native vegetation) and wetlands have been converted to cropland and development. Both rangelands and wetlands emit significant amounts of carbon when degraded, but can be restored relatively easily, turning back decades of mismanagement, and regaining their carbon capturing capabilities. We can use plants’ natural appetite for carbon to safely store it while improving the health of our water and soils at the same time.

Save the Bay is working towards the goal of restoring 100,000 acres of tidal marsh habitat around the San Francisco Bay, in order to regain a healthy bay and all its ecosystem services. The Bay has lost 90% of its original tidal wetlands, releasing over 2 billion tons of carbon dioxide. Save the Bay has previously blogged about the carbon capture qualities of wetlands. Research shows that restored rangelands have the ability to capture carbon as well, and it doesn’t take much to restore them.

In the last quarter of a century, over 1950km2 of California rangeland habitats were lost. Rangelands emit carbon not only when converted to other uses, but also when mismanaged, such as through plowing, overgrazing or poor agricultural practices. Native grasslands, primarily through the plants’ extensive and deep root system, are an effective carbon sink, but plowing and converting that land to annual row crops leads to the emission of 20 to 75 metric tons of carbon dioxide per acre.

The Power of Compost

A one-time dusting of compost can make a big difference in restoring degraded rangeland. A study by Rebecca Ryals and Whendee L. Silver concluded that if a thin layer of compost was spread on a quarter of California’s rangeland, the soil could absorb three-quarters of California’s total annual greenhouse gas emissions. The compost fertilizes the soil and improves the soil’s moisture holding capacity, leading to increased plant growth. Through photosynthesis, the plants transfer carbon dioxide from the air into the soil through their roots and decomposing plant material. More carbon in the soil brings greater fertility and water retaining qualities, leading again to greater plant growth, thus sparking an ongoing cycle of regeneration.

From a single application of compost, they found a 50% increase in plant production, leading to an average increase of 1 ton of carbon sequestration per hectare over 30 years. Not only does this provide a relatively easy, low-tech way to launch a positive feedback loop that could play a role in mitigating the effect we’re having on this planet, but you also get increased soil fertility, improved water absorption and retention, and an increase in native plants which provide food for wildlife. Plus, compost can be used to help restore both grasslands and tidal wetlands.

Tidal wetlands have a similar effect. In fact, wetlands store more carbon per unit area than any other ecosystem. Researchers estimate that while grasslands can sink up to 2,000 pounds of carbon per acre per year, wetlands can store up to 5,100 pounds of carbon per acre per year. Similar to the numerous benefits of restoring grasslands, by restoring wetlands we not only sequester carbon, but also absorb floodwaters, reduce storm damage, preserve open space, provide habitat and feeding grounds for a wide variety of species and improve water quality. What’s not to love?

On dry land and wetland, offsetting carbon while increasing biodiversity, improving water quality, providing habitat and improving the environment’s ability to react to climate change is a win-win solution. Clearly, it’s worth our while to conserve and restore rangelands and wetlands, not only to for long-term carbon storage, but also for the numerous additional services they provide. There’s a speck of hope in a sprinkle of compost.

You can get up close and personal with the magic powers of compost through Save The Bay! We use compost to help our native seedlings to grow at our restoration sites around the San Francisco Bay. Learn how you can volunteer with us here.

Smithsonian Study Documents Ability of Wetlands to Fight CO2 Emissions

Kirkpatrick Marsh
The Smithsonian’s 19-year study focused on Kirkpatrick Marsh, located along a subestuary of the Chesapeake Bay. The study highlights the ability of wetlands to fight global warming by absorbing CO2 (Photo Credit: KristenM/Smithsonian Environmental Resource Center).

When thinking about the Bay’s wetlands, you may picture beautiful vistas of pickleweed, saltgrass, and rushes teeming with wildlife.  You may also ponder the way that wetland vegetation filters trash and pollutants from the water entering the Bay, enhancing water quality for fish, sharks, and porpoises, or the invaluable flood control that wetlands provide to Bay Area cities.  But what might not come to mind is the fact that wetlands are also busily engaged in an activity that offers another kind of protection for our communities – capturing carbon dioxide (CO2).  Scientists have documented the ability of tidal wetlands to act as a sink for this greenhouse gas, and a recently published study by the Smithsonian Institution provides evidence that wetlands could be important allies in the fight against climate change.

Over two-and-a-half decades ago, researchers at the Smithsonian Environmental Research Center in Maryland began investigating how wetland vegetation would react if the amount of carbon dioxide in the atmosphere doubled.  Now the results of a 19-year study are in, and it is clear that wetland plants have risen to the challenge.

Scientists discovered that as CO2 levels increase, so does the amount of carbon taken in by wetland plants.  Plants absorb carbon to generate energy and obtain the building blocks needed for growth and maintenance.  In addition to being used within the living plants, carbon can also be stored in the soil.

One of the wetland plants included in the Smithsonian study, a California native known as American bulrush, extracted an average of 32% more carbon from the atmosphere under higher levels of CO2.  The bulrush absorbed more carbon during the day and also released less carbon back into the atmosphere at night.

This cutting-edge science suggests that protecting, enhancing, and restoring the Bay’s wetlands presents a natural and effective way to combat climate change on multiple fronts.  Healthy, functioning wetlands provide protection against rising seas and a means for reducing the amount of climate-altering CO2 in the atmosphere, allowing us to both adapt to climate change and reduce its impact.

American bulrush is present in San Francisco Bay, and can even be found at one of Save The Bay’s restoration sites!  To get up close and personal with wetland vegetation and play a part in helping the Bay Area combat climate change, volunteer with Save The Bay’s Restoration Program!