Can coastal restoration slow climate change?

Can concern about climate change help stop coastal habitat loss? Will coastal restoration help stop climate change? A growing number of observers from California to Indonesia believe that the answer to both questions is yes.

A little over a decade ago, the United Nations Framework Convention on Climate Change recognised that different land use activities, especially slash-and-burn deforestation, were contributing significantly to greenhouse gas (GHG) pollution in the atmosphere. In response, the Intergovernmental Panel on Climate Change (IPCC) created guidelines to help countries track emissions from their Agriculture, Forestry and Other Land Use sectors, and the UN Reducing Emissions from Deforestation and Forest Degradation Programme (UN-REDD) was launched, allowing developed countries to pay developing countries to protect their remaining forests. Private sector groups and non profit groups, including Verified Carbon Standard (VCS), also joined this effort, allocating offset-credits to forestry projects that limited GHG emissions relative to a business-as-usual baseline. In many cases, individuals who purchased credits to offset their carbon footprints also helped fight deforestation.

These efforts to protect the green carbon in terrestrial forests have achieved some success, but forests only account for part of the global carbon cycle. In comparison, roughly 83% of the carbon cycle passes through the ocean. Some of that carbon causes ocean acidification, but a portion is ultimately removed from circulation by a dwindling number of coastal plant communities that transfer the carbon to coastal sediments. Can offset-credits analogous to those used to protect forests help protect this blue carbon currently stored by salt marshes, mangrove forests and seagrass meadows?

Half of the human population now lives less than 60km from the ocean, creating development pressures that impact coastlines. Many coastal areas also suffer from fertiliser run-off from distant farm fields which impacts water quality. Coastal algae blooms kill animals and block light for submerged grass beds. An estimated one third of the world’s seagrass meadows have disappeared since the 1800s. When marshes and seagrass meadows disappear, most of the carbon they store is ultimately released back to the atmosphere. These coastal habitats are not as geographically extensive as terrestrial forests, but they often contain much higher concentrations of carbon in their soils. A recent study estimated that seagrass meadow loss alone could potentially emit almost 300 Teragrams of carbon every year, roughly equivalent to the annual energy sector emissions from Japan.

Several countries have taken steps to protect mangrove forests through UN-REDD, and the IPCC recently created a set of GHG accounting guidelines to assist countries that want to include ‘blue carbon’ in their national GHG inventory reports. However, a global framework for extending offset-credits to marshes and seagrass meadows was lacking.

A tool in the fight against climate change

In 2012, I joined a team organised by Restore America’s Estuaries tasked with creating the first offset-credit accounting guidelines for coastal ‘blue carbon’ habitats. My current adviser and I wrote the seagrass sections for the resulting Methodology for Tidal Wetland and Seagrass Restoration, which was recently approved for use by VCS, the world’s largest supplier of voluntary carbon credits. VCS-issued credits can now help finance seagrass restoration projects anywhere in the world, which will hopefully incentivise restoration projects to go forward that might not otherwise be cost-effective.

We added a number of provisions to the Methodology to address different challenges related to GHG accounting underwater. One of these challenges involved determining whether seagrasses increase methane production, a harmful GHG. Methane release is typically negligible in marine systems; however, methane causes 25x more warming than the same amount of CO2, so we required projects to account for a possible methane increase. We also addressed the fact that underwater currents potentially move seagrass seeds over a large area, so it might be difficult to determine whether new meadow patches resulted from the restoration or from nearby, natural meadows. In both of these examples, we encouraged managers to measure all aspects of their ecosystem directly, but we also provided options for conservatively estimating a project’s net GHG benefit if particular measurements prove cost-prohibitive.

The Methodology was circulated at the UN climate change meeting in Paris (COP21) and has already assisted a mangrove restoration project in Indonesia. More ‘blue carbon’ projects will likely follow in the near future. California recently passed legislation creating a seagrass restoration programme for climate mitigation. Our team is now working to integrate ‘blue carbon’ provisions into an existing VCS REDD methodology, which we hope will ultimately incentivise both the restoration and conservation of natural habitats.

*Matthew Oreska [2008] did an MPhil in Biological Sciences with the support of a Gates Cambridge Scholarship. He subsequently worked for the Smithsonian Institution and is now a PhD candidate at the University of Virginia, working on coastal restoration. The Methodology was created by Dr. Igino Emmer, Silvestrum; Dr. Brian Needelman, University of Maryland; Steve Emmett-Mattox, Restore America’s Estuaries; Dr. Steve Crooks, Environmental Science Associates; Dr. Pat Megonigal, Smithsonian Environmental Research Center; Doug Myers, Chesapeake Bay Foundation; Matthew Oreska, University of Virginia; Dr. Karen McGlathery, University of Virginia; and David Shoch, Terracarbon. Photo credit: B. Shayka.