Mangrove seen as weapon in climate war


Mangroves in Sipacate-Naranjo National Park, located on Guatemala’s Pacific coast. (Ana Giró, courtesy of Healthy Reefs for Healthy People)

To the untrained eye, the mangroves of the Gulf of California appear to be little more than ragged bushes held aloft by scraggly, finger-like roots rising from the shallows. At the right times of year, some of the millions of migratory shorebirds that visit from as far away as Alaska can be seen. The crabs and fish they shelter, however, are more difficult to spot. And less noticeable still are the underlying peaty soils that have accumulated over time, in some cases millennia, helping to make mangrove stands among the most carbon-rich ecosystems on the planet.

But Mexico’s coastal communities and national government are taking note. They are coming to appreciate the teeming life in mangroves and the valuable ecosystem services they provide. And they are increasingly ambitious about conserving existing mangrove stands and restoring degraded and cleared ones as a means to generate carbon credits on international markets. “Mangroves have become very important for people in Mexico,” says Fernanda Adame, an aquatic ecologist at the Australian Rivers Institute of Australia’s Griffith University. “They understand mangroves not only harbor commercially important fish and mollusks, filter pollution, and serve as a first line of defense against hurricanes. They also are one of the most important sites for greenhouse gas mitigation.”

Last year, WILDCOAST, a U.S.- and Mexico-based nongovernmental organization, joined Mexico’s National Commission of Protected Natural Areas (Conanp) to initiate a project aimed at conserving and managing some 28,925 hectares (71,475 acres) of mangroves in the states of Baja California Sur, Sonora and Sinaloa. The idea behind the project, supported in part by the Leonardo DiCaprio Foundation, is to use mangrove management to generate certified carbon credits based on the prevention of greenhouse-gas emissions that would result if the mangroves were cut down. The credits would be sold on the voluntary carbon market, in which businesses purchase such credits voluntarily as a means of offsetting emissions from their operations and burnishing their environmental credentials.

Income from the carbon sales would be used to pay rangers, carry out educational programs and restore and manage mangroves at the site in collaboration with Conanp. Annual estimated income from the project, experts say, could approach US$800,000. Most importantly, the initiative could show how mangroves might contribute to achieving Mexico’s goal of reducing annual greenhouse gas emissions by 22% over the next 12 years. “This is an amazing project, which can demonstrate the high potential for using credits from mangroves on the carbon market and help Mexico achieve its ambitions in reducing greenhouse gas emissions,” says Adame, who is managing the scientific aspects of the project.

Other Latin American countries also have their eyes on mangrove conservation and restoration, including through carbon trading. Indonesia has the greatest extension of mangrove cover in the world, but Brazil ranks second, and Mexico fourth. Ecuador, Colombia, Venezuela, Cuba, the Dominican Republic and the nations of Central America also have extensive mangrove stands. Experts say this means Latin American countries have significant opportunities to restore mangroves as a way of bolstering fish habitat, improving hurricane protection and sequestering carbon in fulfillment of climate-change goals. “After years of perceiving mangroves as little more than wastelands from which to extract resources like wood for construction and cooking, there’s growing political will to protect and restore mangroves in Latin America,” says Steven Canty, an expert on marine conservation at the Smithsonian Marine Station in Fort Pierce, Florida. “There’s legislation in many countries to prohibit mangrove cutting and [there are] significant restoration efforts.”

Conservation concessions

In Ecuador, some 70% of the country’s mangroves were destroyed beginning in the 1960s as firms from the United States, Europe and Asia moved to establish shrimp ponds in their place along the Pacific Coast. Mangroves fell to chainsaws, bulldozers and fires, and thousands of villagers who made a living from fishing, collecting shellfish and other activities enabled by the mangrove ecosystem were driven from their homes. But in 2014, the government established the Socio Manglar project, in which coastal communities can be awarded concessions and receive performance-based payments from the government for preserving mangrove stands. With management rights to some 40,000 hectares (99,000 acres) of the nation’s remaining 160,000 hectares (395,000 acres) of mangroves, such communities have reported increased fishing harvests. Experts say the country could be a good candidate to parlay mangrove conservation into carbon credits in international markets.

In the Dominican Republic, meanwhile, where the United Nations Food and Agricultural Organization reported some of the highest percentage losses of mangroves in the Americas during 1980-2007 (an average 2.8% annually), a new understanding has taken shape. After watching mangroves being replaced by agricultural operations and tourist developments, the government allowed Counterpart International, a U.S.-based nongovernmental organization, to quantify the amount of carbon stored in mangroves of the 550-square-kilometer (212-sq.-mile) Montecristi National Park on the country’s northern coast. Data from the study, issued in 2014, eventually could help enable the country to receive climate funding for local communities interested in conserving and restoring mangrove areas.

Governments increasingly eye mangrove conservation and restoration as a means of combating global warming because of the ecosystem’s ability to stockpile up to four times as much carbon per square meter as rainforest trees and plants. Unlike rainforests—in which almost all carbon is stored in trunks, branches and leaves, then released when these die and decompose—mangroves can keep over 90% of their carbon in the soil. That’s because this soil is submerged much of the time, which means little oxygen is present to help microbes break down the organic matter that mangroves deposit. Instead, a slow but steady process of carbon build-up occurs. Mangroves drop their leaves and branches, roots die, and the detritus accumulates over thousands or tens of thousands of years without fully decomposing, the carbon locked in. Indeed, mangroves—along with freshwater peatlands and the frozen, permafrost soils that occur especially in or around the Arctic—are the most carbon-rich ecosystems in the world.

Still, carbon trading in mangroves has not taken off in the way many environmentalists had hoped. Carbon storage in mangroves depends on a huge number of factors including climate, species, canopy height, exposure to mineral sediment and the specific location of the mangrove stand in the tidal zone. It can vary dramatically even within a few kilometers. Many nations lack the resources or technology to accurately gauge all those factors. In fact, of the 107 countries with mangroves, only around 40 have the necessary field data, experts say.

International agreements also have failed to keep up, largely because until now there has not been a reliable means of measuring carbon in mangrove soils. Most greenhouse-gas mitigation efforts in tropical woodlands revolve around the Clean Development Mechanism (CDM) or REDD+ (Reducing Emissions from Deforestation and Forest Degradation). These allow developed countries to fund reforestation, afforestation and, in the case of REDD+, conservation efforts in the developing world. Mangroves can be included in those efforts under the Paris Agreement of 2015. But mitigation measures to date only include the carbon in the mangroves’ woody vegetation, even though it is in the soil, not the woody vegetation, where the vast majority of mangrove carbon lies.

This now could be changing. In April of this year, Jonathan Sanderman of the U.S.-based Woods Hole Research Center and 23 other researchers from around the world published in the journal Environmental Research Letters what many experts consider among the most comprehensive views of global mangrove carbon storage. Drawing on satellite data concerning climate, vegetation, hydrology and other key variables, the researchers developed a machine-learning model to predict such storage, using remotely sensed deforestation maps to calculate it for all 107 mangrove nations.

“This research allows us to capture the wide variability of carbon storage in different mangrove species at different locations,” says Sanderman, an associate scientist at the Center. “It should help design programs aimed at emissions reductions and carbon sequestration.”

A necessary step forward, experts say, is updating countries’ carbon inventories so they take into account mangrove soil and serve as a more accurate baseline for climate mitigation efforts. A recent paper by Adame and coauthors, for example, estimates that the average carbon stock in Mexico’s mangroves is 31 times greater than that reported by Mexico to the United Nations as part of its climate commitments.

Another required advance lies in refining methods not only to gauge carbon storage, as is currently happening, but also to estimate carbon loss when mangroves are cleared or degraded. Those losses are significant when mangroves are cut down for heating and fuel. They are much higher—more than 90%—when mangroves are removed for shrimp aquaculture, since this involves excavation of mangrove soils to accommodate ponds.

Voluntary markets may still accept mitigation projects with rough estimates of those emissions. But more precise measurements will likely be needed to get mangrove soils included in United Nations-approved trading mechanisms or the European trading system and to boost enthusiasm for mangroves in markets generally, experts say. “Carbon markets are all about certainty, and if they don’t have confidence in the amount of carbon they’re buying, there’s not going to be a decent price,” Sanderman says.

Recognizing storage value

Many experts nevertheless believe the day for mangrove carbon is coming. And with the estimated annual value per hectare of standing mangroves in the region as high as US$37,000 when ecosystem services like storm protection and fisheries are taken into account, they are making ever greater efforts to protect them. Latin American countries have passed strict laws prohibiting the cutting or removal of mangroves, and have earmarked coastal areas for protection under the Ramsar Convention on Wetlands of International Importance. They also have established marine protected areas that frequently encompass mangroves. There have been significant restoration efforts, with local communities often planting mangrove seedlings and digging channels to ensure the necessary mix of fresh water and saltwater for mangroves to thrive.

Despite such progress, the advance of sugarcane and African palm plantations, as well as ranching, shrimp aquaculture and tourism development have continued to deplete Latin America’s mangrove stands. In southwestern Guatemala, for example, palm and sugar plantations have been illegally diverting water from the Madre Vieja River basin to irrigate their plantations over the last few years, spurring protests by hundreds of small-scale farmers and fishermen concerned about their own harvests and the long-term impact on Pacific mangroves in the area. Guatemala’s Ministry of the Environment and Natural Resources (MARN) has moved to halt the companies’ activities, but elsewhere in Guatemala a lack of resources makes surveillance and monitoring virtually impossible, experts say. According to Sanderman’s research, Guatemala during 2000-12 lost nearly 6% of its mangrove cover, placing it third behind Malaysia and Myanmar in percentage losses worldwide, and sustained the world’s highest percentage of mangrove carbon loss.

Ana Giró, Guatemalan coordinator for the Healthy Reefs for Healthy People Initiative (HRI), a consortium of governmental and nongovernmental organizations, perceives the government as more aware of the threat now than in the past. But, she says: “Where I work, on the Caribbean side, the problem has gotten worse over the years, and the cutting of mangroves is much faster than their restoration.”

Mexico makes progress

Mexico is widely considered one of the world leaders in mangrove conservation, with a robust system of monitoring and surveillance, numerous restoration projects and a 2006 law that makes mangrove cutting a criminal offense meriting jail time. New attitudes there have made a difference, experts say. After massive losses on both the Caribbean and Pacific sides of the country in the 1980s and 1990s, mangrove deforestation dropped precipitously to 0.67% in the period 2000-12.

Still, abuses do continue to occur. During the course of one night in January 2016, developers backed by the Mexican tourist board, Fonatur, and protected against protestors by police officers cleared 59 hectares (146 acres) of mangroves on the edge of the city of Cancún to make way for apartments, hotels and shopping malls as part of a project called Malecón Tajamar. Continuing protests and negative press coverage ultimately killed the project, but the damage had been done.

Corruption is often present, experts say. “In much of Latin America—as in the world—more laws and enforcement are in place,” says Alfredo Quarto, international program and policy director of the nonprofit Mangrove Action Project (MAP). “But there’s still a lot of illegal encroachment. Bribery can too often still get you a hotel or shrimp farm in an area reserved for mangrove protection.”

It remains unclear how this and other issues, such as community rights of mangrove dwellers, will be dealt with as carbon markets for mangroves develop. But for now, efforts to protect and restore mangrove stands seem to be gaining momentum, providing a sharp contrast to the days not so long ago when mangroves were seen as little more than malodorous swamps.

- Steve Ambrus

Index image: In Guatemala, human impacts on mangroves range from land-clearing for salt ponds to the extraction of firewood. (Cesar Coxic, courtesy of Healthy Reefs for Healthy People)

Fernanda Adame
Research Fellow
Australian Rivers Institute
Griffith University
Nathan, Australia
Tel: +(61 7) 373-57101
Steven Canty
Program Coordinator for Marine Conservation Program
Smithsonian Marine Station
Fort Pierce, FL, United States
Tel: (202) 633-1615
Ana Giró
Guatemalan Coordinator
Healthy Reefs for Healthy People Initiative (HRI)
Guatemala City, Guatemala
Tel: +(502) 5314-8806
Alfredo Quarto
Program and Policy Director
Mangrove Action Project (MAP)
Seattle, WA, United States
Tel: (360) 452-5866
Jonathan Sanderman
Associate Scientist
Woods Hole Research Center
Falmouth, MA, United States
Tel: (508) 444-1505