Wetlands on the Move

Wetlands on the Move 1
Tidal marsh wetlands, like those at Eden Landing in Hayward, are one solution to mitigate the effects of Sea Level Rise.


Under current conservative projections, sea level will rise  1.0 to 1.4 meters by the year 2100, which will inundate 200 square miles of low-lying shoreline areas of San Francisco Bay, impacting wildlife, habitat, and millions of Bay Area residents who rely on at-risk infrastructure. The cost of replacing property at risk of coastal flooding with a 1.4 meter rise in sea levels is $62 billion. We already get a glimpse of what this might look like during extreme high tides, commonly called King Tides, which happen a few times a year. The next ones are next week, on December 21-23, 2014.

Tidal marsh wetlands are both part of the solution, and at risk of disappearing. They capture carbon to lessen global warming, and mitigate the effects of sea level rise by buffering us from floods and storms. But thousands of acres of Bay wetlands are at risk of drowning as sea level rises. Wetlands have evolved with sea level rise, and can resist and adapt to it by building up their elevation or moving upland. However humans have interfered with these natural responses, by changing the climate, obstructing sediment delivery and creating obstacles to migration. It is projected that 95% of San Francisco Bay tidal marsh habitat may be drowned by 2100.

Photo by heidi.nutters
The cost of replacing property at risk of coastal flooding with a 1.4 meter ride in sea levels is $62 billion. Photo by heidi.nutters

When marshes flood during high tide, plant roots trap mineral sediment from the water, adding new soil to the ground. As sea level rise accelerates and flooding occurs more often, marshes can react by building soil faster. Below ground, the growth and decay of plant roots adds organic matter as well. Given access to sediment rich waters, wetlands can gain elevation, keeping pace with sea level rise. If sediment delivery to a wetland is cut off or reduced due to upstream restrictions, tidal wetlands can no longer build soil to outpace rising seas, and will drown.  Sediment flow has been disrupted by development, landfills, and levees around the bay, while upstream dams and reservoirs reduce sediment load by 20%. 

Another natural response to sea level rise is migration. As sea levels rise, current wetlands can go underwater, while new mudflats are constructed and new tidal zones grow upland. This is possible if there are no obstacles impeding the wetlands migration. Examples of obstacles are roads, railroads, levees and buildings. Ironically, conventional ways of protecting coastal properties, such as dikes and seawalls, impede wetland migration, and in some cases increasing vulnerability to floods and storms. It is estimated that the San Francisco Bay wetlands require approximately 93 square miles (60,000 acres) of land into which they must migrate to survive a sea level rise of 1.4 m.  (See Map of SF Bay county viable accommodation areas for wetland migration.)

Whether wetlands continue to survive rising seas depends largely on us.  In order to ensure the long term viability of our wetlands, we need to protect their sediment delivery, as well as preserve the inland areas to ensure their viability as wetland habitat in the future. This means halting development adjacent and directly inland to wetlands, planning our cities with an eye towards sea level rise and wetlands survival, and building smarter flood controls using horizonal levees fronted by wetlands.

Scientists agree that the Bay needs 100,000 acres of tidal marsh to thrive. Less than half that exists.  Save The Bay is working to double the amount of Bay tidal marsh over the next ten years, while continuing to battle development that not only threatens current and restorable wetlands,  but also the future viability of those wetlands as we and they adapt to sea level rise.

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.