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A fragile carbon sponge
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The dominant mangrove species in Gazi Forest is Rhizophora murcronata. With oval, leathery leaves about the size of a child’s palm and spindly branches that reach to the sun, the trees can grow up to 27 meters tall. Their interlaced roots, which grow from the base of the trunk into the saltwater, make these evergreen trees unique.Salt kills most plants, but mangrove roots separate freshwater from salt for the tree to use. At low tide, the looping roots act like stilts and buttresses, keeping trunks and branches above the waterline and dry. Speckling these roots are thousands of specialized pores, or lenticels. The lenticels open to absorb gases from the atmosphere when exposed, but seal tight at high tide, keeping the mangrove from drowning. The thickets of roots also prevent soil erosion and buffer coastlines against tropical storms. Within these roots and branches, shorebirds and fish — and in some places, manatees and dolphins — thrive. Mangrove roots support an ecosystem that as inland forests. That’s because the saltwater slows decomposition of organic matter, says Kipkorir Lang’at, a principal scientist at the Kenya Marine and Fisheries Research Institute, or KMFRI. So when mangrove plants and animals die, their carbon gets trapped in thick soils. As long as mangroves stay standing, the carbon stays in the soil. Robust estimates of mangrove forest area in Kenya before 1980 are not available, Lang’at says. However, with the clear-cutting of mangrove forests in Gazi Bay in the 1970s, he says, the area was left with vast expanses of bare, sandy coast. Other parts of the country experienced similar losses: Kenya between 1985 and 2009 because no mechanism existed for their protection. The losses had a steep price: Just as mangroves absorb more carbon than inland forests, when destroyed, they release more carbon than other forests. And since the mangroves provided habitat and shelter for fish, their destruction meant that fishers were catching less. Recognizing this high cost, as well as the ecosystem’s other benefits, Kenya’s government ratified the Forest Conservation and Management Act of 2016, a law protecting mangroves and inland forests. Cutting down mangroves is now banned throughout the country, except in very specific areas under very specific circumstances.
Available data suggest that Kenya’s rate of mangrove loss has declined in the last two decades. The country is now losing about 0.65 percent of its mangrove forest annually, according to unpublished evaluations conducted in 2020 by KMFRI. Since the turn of the millennium, as well, hovering between a loss of 0.2 and 0.7 percent per year, says a 2020 study in Scientific Reports.Mikoko Pamoja offers hope for turning around those declines. The project, whose Swahili name means “mangroves together,” has its roots in a small mangrove restoration effort that started in 1991 in Gazi Bay, spearheaded by KMFRI. The effort evolved into a scientific experiment to see what it would take to restore a degraded ecosystem. It attracted collaborators from Edinburgh Napier University, Europe’s Earthwatch Institute and other organizations across Europe. Now, Gazi Forest boasts 615 hectares of mangrove forest, including 56,000 individual seedlings planted by the community. Plans to plant more mangrove trees — at least 2,000 per year — are in the works.
Creating carbon creditsGazi Forest siphons carbon from the atmosphere at a rate of 3,000 metric tons per year, says Rahma Kivugo, the outgoing project coordinator for Mikoko Pamoja. These aren’t merely ballpark numbers: To sell the carbon offsets collected by Mikoko Pamoja, forest managers must calculate the amount of carbon stored by mangroves. Volunteers venture into the forest twice a year, checking on 10 selected 10-square-meter plots in the wild forest and five plots in planted forest. Workers measure the diameter of mature trees at an adult’s chest height. They then estimate the trees’ height. Finally, they classify young trees as knee-height, waist-height, chest-height and higher. From these observations, researchers estimate the volume of mangrove material above ground in each plot and extrapolate for the whole forest area. Once they have an idea of the volume of plant material above ground, team members can estimate root volume below ground using a standardized factor specific to mangrove forests, says Mbatha Anthony, a research assistant at KMFRI in charge of carbon accounting. Even though mangrove forests store a lot of soil carbon, the project calculates carbon stored only by the tree itself because “calculating soil carbon is a resource-intensive undertaking for a small project like Mikoko Pamoja,” Anthony says. With an estimate of the total volume of biomass in the forest in hand, “we can then translate that into tons of carbon,” says environmental biologist Mark Huxham of Edinburgh Napier University, who helps Mikoko Pamoja with its calculations. In general, 50 percent of aboveground biomass is carbon. Below ground, 39 percent of biomass is carbon. The amount of carbon stored by Gazi Forest is then relayed to the , a group based in Scotland that certifies carbon calculations. Once its calculations are certified, Mikoko Pamoja receives Plan Vivo Certificates, or PVCs. One PVC is equivalent to one metric ton of carbon dioxide emission reductions. These PVCs are submitted to the Association for Coastal Ecosystem Services — an organization that markets carbon credits for Mikoko Pamoja and similar projects. Through ACES, Mikoko Pamoja’s PVCs can then be purchased by anyone who wishes to offset their carbon emissions. Roughly 117 hectares of Gazi Forest have been demarcated for the sale of carbon credits. “Mikoko Pamoja generates approximately $15,000 annually from the sale of carbon credits,” Anthony says. From 2014 to 2018, the project generated 9,880 credits — 9,880 tons of avoided carbon dioxide emissions.
A community at workMikoko Pamoja sells carbon credits at more than $7 per ton. Revenues get split in a clearly defined manner, according to what residents decide are pressing needs of Makongeni and Gazi villages. Around 21 percent pays wages of residents involved with Mikoko Pamoja. And “more than half of what is earned goes toward community projects,” Kivugo says. In total, about $117,000 has gone to community projects since Mikoko Pamoja was founded. These projects include donating medicine to health clinics and textbooks to schools and digging clean water wells. Plans are under way to revive a windmill in Gazi for pumping water and renovate Makongeni’s primary school. “The need in the community is great. So carbon trading is unlikely to meet all the needs,” Huxham says. But the funds make a significant contribution to local livelihoods, which primes the community to support conservation, he says. The approach seems to be working. On a winding path into the forest, visitors encounter a signboard, with large letters in Swahili declaring, “Take note! This is a Mikoko Pamoja area protected by the community. Littering is prohibited! Trimming trees is prohibited!” Active community participation is central to Mikoko Pamoja’s success. Not only do community members plant mangrove seedlings and survey trees to gauge carbon storage, community scouts monitor the health of this ecosystem. Scouts clean up litter within the forests and survey the forest’s biodiversity. From a wooden watchtower above the forest, scouts also track and report illegal logging. “Should we spot suspicious activities in the forest, we will call the Kenya Forest Service rangers, who have the authority to detain and arrest any trespasser,” says local scout Shaban Jambia.
Back at the boardwalk, Hamadi leads a small knot of visitors through the mangroves, pausing occasionally to touch a tree’s waxy leaves. She plucks a propagule — a dark-brown pod longer than her hand — from a tree belonging to the mangrove species Bruguiera gymnorhiza.She drops the propagule over the boardwalk’s handrail, into the soft marsh soil about 1.5 meters below. It lands, sticking almost perfectly perpendicular in the ground. “This will soon take root and germinate into a new plant,” she explains to the visitors. “That’s how this species propagates.” Hamadi, the tour guide, is one of 27 members of the Gazi Women Mangrove Boardwalk group. Members offer interpretive services to visitors for a fee. The women also prepare Swahili cuisine for sale to groups visiting the area. “A dish of coconut rice served with snapper fish is particularly popular, washed down with flavored black tea or tamarind juice,” says Mwanahamisi Bakari, the group’s treasurer. These ecotourism efforts have attracted international support. The World Wide Fund for Nature Kenya, for instance, constructed a conference facility, which the women’s group rents to those who want to use the location as a backdrop to discuss sustainability efforts.