Kenya’s Mangrove Credits Restore Coasts and Revive Lives

By Juliet Akoth Ojwang/Mongabay

The scorching afternoon sun stretches across the semiarid landscape of Marereni, in Kenya’s Kilifi county, where salt and sea shape both the land and the lives that depend on it.

Known for its extensive salt mining operations, this remote settlement lies at the heart of the country’s north coast salt belt. Yet beyond the glint of salt pans, Marereni is also home to one of the coast’s most vital ecosystems: a mosaic of fringing, estuarine and creek mangrove forests that support rich biodiversity. This is the stunning backdrop to the site of restoration projects aimed at both revitalizing these important mangroves — and the communities that tend to them.

In Marereni, Kenya, a marine biodiversity credit program by Seatrees and COBEC is restoring mangroves and livelihoods. Through $3 “biodiversity blocks,” locals plant trees, boost incomes, and rebuild coastal resilience. Despite challenges, the project reports high survival rates and rising fish stocks.

In recent years, Marereni’s mangroves have been disappearing due to conversion pressure for solar salt works, aquaculture and human settlement, according to information from the Kenyan government’s National Mangrove Ecosystem Management Plan 2017-27. The plan underscores that the loss of mangrove cover significantly weakens coastal protection, leaving shorelines more susceptible to erosion, storm surges and rising sea levels. This not only heightens the vulnerability of inland areas and infrastructure to climate-related risks but also disrupts vital marine ecosystems, degrading crucial breeding and nursery grounds for fish, crustaceans and other species, leading to declining fish stocks and reduced biodiversity.

For coastal communities, such as those in Marereni, the loss of mangroves threatens their very livelihoods. Many depend on mangrove ecosystems for fisheries, fuelwood, construction materials and a range of other vital services. As the mangroves vanish, so do economic opportunities, exacerbating poverty and food insecurity in these communities.

^{A salt pond situated next to a former mangrove habitat in Marereni. Underground seepage from the pond raises salinity levels beyond the mangroves’ tolerance, leading to death. | Photo by Juliet Ojwang.}

Since 2022, a California-based nonprofit organization called Seatrees has been working with communities in Marereni to restore and protect coastal and marine ecosystems as a natural solution to climate change. This follows similar work the organization began in 2020 in another coastal location called Mida Creek.

Most of Seatrees’ projects globally have been funded through traditional means, including corporate and individual donations and grants. But in 2024, Seatrees started offering donors the option of buying $3 “biodiversity blocks,” each of which represents a single tangible conservation action: planting one mangrove tree on site in Marereni.

Seatrees touts these “blocks” as part of the world’s first marine biodiversity credit program, designed to restore and protect natural marine ecosystems that historically have been relegated to the sidelines of conservation funding.

The concept of marine biodiversity credits comes on the heels of recently developed land-based biodiversity credit programs, which fund projects such as forest conservation and species habitat restoration. They work by assigning financial value to measurable conservation outcomes, allowing buyers to support specific biodiversity gains in exchange for standardized biodiversity credits. These credits can then be used by companies or individuals to meet voluntary environmental targets or demonstrate a commitment to biodiversity stewardship.

When asked, Kevin Whilden, co-founder and director of Seatrees, says the goal of their project is to shift conservation financing away from one-time donations and toward a long-term, scalable model.

On the ground in Marereni, so far, Seatrees has issued 300,000 marine biodiversity credits totaling $900,000, mostly through individual buyers and small companies. A Seatrees count earlier in 2025 showed they had already planted 190,000 mangrove trees, with 30,000 new trees planted each month. Seatrees estimates all 300,000 mangrove biodiversity blocks will be planted by July.

Restoring Marereni’s mangroves

Muyu wa Kae is an area within the Seatrees restoration site, which covers 600 hectares (1,483 acres). The work here is carried out in partnership with a local NGO called Community Based Environmental Conservation (COBEC). Seatrees sends funding to COBEC, which implements projects on the ground.

COBEC’s approach goes beyond just planting trees. The organization works directly with local communities, ensuring they benefit from restoration efforts. “You can’t implement conservation projects without community participation,” says Edward Mwamuye, COBEC’s program manager. “We invest in livelihood enhancement programs such as smart agriculture, beekeeping and small businesses.”

^{From right: Edward Mwamuye, program manager at COBEC, engages with Julius Sila, the organization’s GIS expert. | Photoby Juliet Ojwang.}

Community members form their own groups and turn mangrove restoration into a livelihood by establishing and maintaining mangrove nurseries. COBEC and Seatrees support the groups by providing some materials used in growing propagules, which group members nurture over the course of several months until they are ready for planting. COBEC then purchases the saplings for its Seatrees project sites, where mangroves have been degraded from tree cutting for fuel and home construction, sand deposition or livestock grazing. (The nurseries also sell to other organizations.) With the income earned, some groups are able to start small side businesses such as goat rearing.

Currently, there are more than 30 project groups in Marereni involving 640 community members (218 men, and 422 women). These groups cultivate four species of mangrove native to the Kenyan coast: Rhizophora mucronata, Avicennia marina, Ceriops tagal and Bruguiera gymnorrhiza. This initiative has become the primary income source for participating community members.

^{Zena Hamisi, an environmentalist and Marereni resident, is one of the community members employed to lead mangrove restoration efforts under the Seatrees marine biodiversity credits project | Photo by Juliet Ojwang.}

Zena Hamisi, chairperson of the Neema Muslim Women Group in Marereni’s Mto wa Mawe Creek, says the project has uplifted her and her fellow members. “COBEC has held our hand and supported us to a point where we now earn income,” she says. Each sapling sells for 20 shillings (about $0.15). Half the earnings are shared among group members and the other half go into a savings account for other income-generating projects.

“Marereni residents’ main source of income is fishing, and when mangrove numbers declined, fish catches also went down. Since we started restoring them, we have seen improvement.” However, illegal mangrove cutting remains a problem, and she calls for more education.

One strategy Seatrees and COBEC use to address illegal deforestation — a major obstacle to mangrove restoration — is COBEC’s Treeducation Scholarship Fund. The initiative offers 300 scholarships over 10 years to members of local communities, aiming to support school fees and the establishment of woodlots to grow non-mangrove trees that could be cut as an income source, helping to shift the logging pressure away from mangrove forests.

“The plan is to maintain and expand the education fund throughout the [10-year] lifespan of the biodiversity blocks project,” says Orion McCarthy, Seatrees’ science lead.

Emmanuel Gona, a Muyu wa Kae fisherman, says that before the restoration efforts, fishers barely caught fish worth 500 shillings (less than $4) per day, but now they can make between 900 and 1,000 (up to $7.75). Research has proven that mangroves often support rich fish and crustacean communities.

However, Gona acknowledges that men’s participation in the conservation effort remains low. His group has only 10 men and 27 women. He suggests that better communication about the project’s importance and better financial incentives could encourage more men to join.

Measuring and monitoring

Seatrees relies on what it calls a “basket-of-metrics” to assess biodiversity improvements and the success of restoration work across its project sites in Marereni and Mida Creek. This includes field surveys by trained COBEC staff to measure mangrove species diversity, root density, canopy cover, juvenile tree density and the height and diameter of mangroves within representative 10-by-10-meter (32-by-32-foot) plots, each containing roughly 200 seedlings, in order to estimate aboveground biomass. They also assess crab and snail diversity and abundance. Scout patrols cover a range that extends across 1,248 hectares (3,084 acres).

In addition, Seatrees collaborates with Ocean Ledger, a London-based remote sensing company, to analyze satellite imagery showing height, canopy cover and aboveground biomass of mangrove trees in a much larger area than COBEC can access on the ground. The two data sources — field assessments and satellite data — are used together, with each helping to validate and strengthen the findings of the other.

Globally, despite widespread investment in mangrove restoration, survival rates remain low, according to a 2022 study, due to inappropriate site selection, limited community engagement and planting in unsuitable hydrological or sedimentary conditions. Yet Seatrees and their partner COBEC report a survival rate of around 80% for their planted mangroves.

Project challenges

Conditions on site in Marereni have presented multiple challenges. COBEC GIS expert Julius Sila, says hydrological changes have hindered restoration efforts in Marereni. “Mangroves thrive in creeks with low wave activity and consistent water exchange from the ocean,” he says. “However, sedimentation has altered the ecology of these creeks, creating obstacles for the restoration process.”

The issue arises when creek water becomes stagnant due to blocked pathways, preventing proper tidal flow. “Mangroves are typically submerged in water for about six hours during the tidal cycle. However, due to hydrological changes and sand deposition, some inlet creeks become blocked. This disruption leads to water stagnation or even drying out of mangroves,” Sila says.

Stagnant water, combined with high temperatures and evaporation, becomes increasingly saline, which can cause mangroves to dry up and die. Additionally, beach erosion displaces sand, which can bury young planted sites, hindering their growth.

Another pressing concern is the pollution caused by underground seepage of saline water from nearby salt pans, which border the extensive mangrove forest in Marereni.

Still, despite these challenges, Seatrees and COBEC remain committed to restoring Marereni’s mangrove forests and ensuring long-term sustainability — and the local communities say they remain committed as well.

The article has been republished from Mongabay: https://news.mongabay.com/2025/07/a-kenya-marine-biodiversity-credit-program-restores-mangroves-and-livelihoods/