BY: Fernando Bretos (2011 Kinship Fellow), Tanya Bryan (2010 Kinship Fellow), and Chelsea Werner (University of Miami graduate student)
Restoring Blue Carbon
There is an analogy that plants are the world’s most remarkable machines. In their terrestrial or marine form, plants not only give us life and prevent an unsavory fate but provide food, energy, and habitats for a growing planet. All at no cost to us! One of the more remarkable features of plants is how they absorb carbon dioxide, a heat-trapping compound, and emit oxygen, that wonderful gas we need to breathe. Increased amounts of carbon dioxide have been shown to be a major contributor to climate change. As a result, efforts to decrease the amount of CO2 in the atmosphere have engaged scientists to understand which types of plants might best be suited to helping with this task. While the common perception is that large terrestrial forests and the soil beneath them are most effective at absorbing carbon, recent research has shown that coastal vegetation, such as salt marshes, mangroves, and seagrasses, are actually much more efficient at storing carbon.
While the common perception is that large terrestrial forests and the soil beneath them are most effective at absorbing carbon, recent research has shown that coastal vegetation, such as salt marshes, mangroves, and seagrasses, are actually much more efficient at storing carbon.
Carbon sequestered by coastal or marine habitats is known as “blue carbon.” Coastal habitats are excellent carbon sinks for several main reasons. First, as mangroves tend to grow in nutrient poor soils they must photosynthesize at a high rate in order to compete. This means they can store a larger amount of carbon in their leaves, roots, and trunks. Secondly, due to the salinity of the marine environment, decomposition is generally slower. As a result more carbon is stored in what is commonly known as peat, the layers of sedimented organic matter that accumulate under mangroves or salt marshes, often up to 10 meters thick. These peat layers accrete with rising sea levels, meaning that theoretically, as sea level increases, so does the volume of these carbon rich mats. Finally, mangroves and sea grasses are highly efficient at trapping sediments using their roots and vegetative layers, which act as sieves for carbon heavy organic matter from adjacent habitats.
While the carbon sequestration value of mangroves, sea grasses, and salt marshes provide an increasingly strong additional argument for their protection, these habitats are still being lost at an alarming rate of 2-7% per year globally. With so many coastal habitats being drained for development or aquaculture ponds, protecting what is left of them is a challenge. While the protection of intact habitats is always preferred, restoring these habitats is becoming an effective option as well. But how can we be assured that restored coastal habitats will be as effective at absorbing carbon as natural coastal habitats are?
Studying the Carbon Sequestration Benefits of Mangrove Restoration
Historically, there have been very few studies looking at how restored coastal habitats compare to established habitats in terms of the amount of carbon sequestered. More recently, two studies, focusing on mangroves, have documented the comparison of these two types of habitats and their carbon sequestration rates. Osland et al (2012) compared restored mangrove areas to natural mangrove areas. The study showed that it takes 20 years for the top 10cm of restored mangrove peat to contain the same amount of carbon as natural mangrove forests. In other words, restored mangroves, while they take a while to get going, are as efficient in trapping carbon as their native relatives in only 20 years after planting. Another study in southeast China (Chen et al. 2012) looked at the benefits of planting more than one species of mangrove in restored areas. The researchers studied the carbon sequestered by a recently restored species of native mangrove (Sonneratia caseolaris) and a non-native species (Sonneratia apetala) in Shenzhen Bay. While the native species grew faster and hence accumulated more carbon in their biomass than the non-native species, the areas planted with both Sonneratia species stored considerably higher levels of carbon in their biomass and peat collectively than areas with only a single species planted. In this instance, by embracing diversity in restoration efforts, more carbon was stored.
It is clear that restoring coastal habitats not only provides a wide range of economic and ecosystem benefits, but there is the added advantage of these habitats continuing to be effective at trapping carbon. More research is required to come to a conclusion but it appears our restoration efforts are paying off in a variety of ways.
Mangrove Restoration in Urban Areas
Located throughout the world in mostly tropical areas, mangroves are found in Florida and some parts of the northern Gulf of Mexico where they exist at the limit of their range. Cold is the limiting factor for these plants but due to climate change, red, and black mangroves are replacing salt marshes in even the northernmost areas of the Gulf of Mexico. Bianchi et al (2013) have found that mangroves, which have woody stems and roots are more effective in storing carbon than the salt marsh grasses they are displacing. Is this a potential benefit of climate change?
In places like Miami, mangroves thrive even in the most urbanized cityscapes. Fortunately, as slow growing as they are, mangroves respond well to restoration efforts. But effective restoration requires a large scale of volunteers to plant seedlings and monitor success. If all goes well, we can then let nature take care of the rest.
The Reclamation Project based at Miami Science Museum is a community based, participatory eco-art project that engages South Floridians to “reclaim” urban ecosystems through the universal appeal of art. The Project is the brainchild of local artist Xavier Cortada. Red mangrove propagules are collected by volunteers during their fruiting season every September. They are then exhibited inside clear plastic cups with tap water along a grid on walls and windows of museums, retail stores and schools throughout South Florida. These conspicuous art installations help Miami residents imagine what the city looked like before the concrete was poured and inspire them to take action.
As such the art installations double as nurseries where the seedlings germinate just long enough to be replanted by volunteers. Once seedlings have been exhibited for a year, volunteers replant them in the summer rainy season at public lands cleared of invasive plants by Miami-Dade County’s Restoration Division. This cycle constitutes a participatory “reclamation” of native habitats by volunteers. To date, 13,000 mangrove seedlings representing over eight acres of coastal habitat have been restored.
Another seven acres of coastal hardwood hammock and coastal riparian areas have been restored by Miami Science Museum volunteers at county and state parks in the past year. The Project recently secured a large grant from Wells Fargo to restore an additional 17 acres of tropical hardwood hammock and coastal dune at Virginia Key, a highly degraded barrier island off the coast of Miami.
The Reclamation Project shows that volunteer restoration brings many benefits. Not only are carbon-loving coastal habitats and the economic benefits given a head start but thousands of volunteers each year are engaged in understanding that there is something they can do to help restore the balance between humans and nature and let nature work for us.
Note from the Editor: Kinship Conservation Fellows, including those who authored this piece, are coming together in mid-April, 2013 for a Tourism, Natural Resources, and Coastal Development Symposium in conjunction with the launch of the Kinship Conservation Fellows Watershed and Coastal Resiliency Affinity Group. They will share expertise around many question, including: Could Blue Carbon principles be applied toward conservation goals? Is the model of a non-profit educational institution replicable? Is there a viable bonefishing market for tourists? What are the opportunities and challenges with land or marine park solutions in this context? For more information about the event, click here. For updates during the week of the symposium, follow Kinship on Twitter and Like Kinship on Facebook.
Fernando Bretos (2011 Kinship Fellow), a marine biologist and environmental educator, is Director of The Reclamation Project at Miami Science Museum. The Reclamation Project is a community-based, participatory eco-art project that empowers South Florida residents to restore urban coastal ecosystems, one seedling at a time.
Tanya Bryan (2010 Kinship Fellow) is the owner of MarLogic Consulting as well as a founding member of BC Blue Carbon, a British Columbia-based initiative focusing on developing blue carbon credits through the conservation of eelgrass. To contact Tanya, email her at email@example.com.
Chelsea Werner is pursuing her MS in Marine Affairs and Policy at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. Her thesis work is focused on an environmental education program with Upward Bound students through the Reclamation Project at the Miami Science Museum. She is also a Resident Scientist in a middle school science classroom and will begin teaching high school science full time this fall.