Restore Coral Reefs across the Osa Peninsula

Costa Rica's Pacific reefs are under threat. The 2023-24 El Niño triggered widespread bleaching and coral loss across the Osa Peninsula, one of the most biodiverse regions in the world. Combined with chronic sedimentation from land use and increasing tourism, these reefs cannot rely solely on nature to recover. They need our help.

To change this, Seatrees has partnered with Raising Coral, a Costa Rican nonprofit that has been restoring reefs in Costa Rica since 2016. Together, we are scaling up a climate-smart restoration program that combines active coral outplanting, rigorous scientific monitoring, and deep community engagement to give these reefs a fighting chance.

This project is structured around the belief that reef recovery and community wellbeing go hand in hand. Raising Coral trains and pays local coral gardeners, hosts annual environmental festivals, and brings local families and tourism operators together around a shared mission of reef stewardship.

About this Project

Seatrees is working with Raising Coral to restore coral reefs in Golfo Dulce and at Caño Island Biological Reserve, off the coast of Costa Rica's Osa Peninsula. Through coral propagation, outplanting, photogrammetry monitoring, and community-based reef management, this project accelerates reef recovery in the face of climate change.

The project focuses on:

  • Rearing and outplanting 1,000 corals per year from 2026 through 2029 across Golfo Dulce and Caño Island (4,000 corals total)
  • Conducting long-term biodiversity monitoring and 3D photogrammetry surveys
  • Reducing bleaching through a rapid response plan involving shading devices, coral nursery depth adjustments, and Reef Star relocation
  • Using elevated Reef Star structures to increase coral survival and provide additional habitat for reef fish 
  • Training and compensating local community members as coral gardeners
  • Hosting environmental festivals and school presentations to build ocean literacy
  • Conducting research using coral reef 3D models to improve restoration in practice
Read the Project Description Here
the threat

Two Reefs, Two Challenges

Golfo Dulce is a deep tropical fjord with unique oceanography. Sheltered from the ocean by the Osa Peninsula, its calm waters look tranquil and inviting. But it rains a lot here (over 20 feet each year!), and sediment runoff from the nearby rainforest and farmland makes the water murky. But some reefs in the gulf have shown resilience to these unique conditions. 

Caño Island sits offshore within a no-take marine protected area. It supports some of the highest coral diversity and fish biomass on Costa Rica, with more than 200 fish species recorded. Even with protected status, the 2023-24 El Niño triggered significant declines in coral cover. Scientists consider active restoration to be essential if Caño is to remain one of Costa Rica's key Pacific reef refuges.

The reefs of both locations are home to endangered species including Porites evermanni (lobe coral), Pocillopora verrucosa (cauliflower coral), hawksbill sea turtles, and scalloped hammerhead sharks. The restoration and monitoring work funded by this project directly benefits these species and the fishing and tourism communities that depend on healthy reefs.

Here's how coral restoration in Costa Rica works:

Resilience-first coral selection

Coral fragments are collected from colonies that survived past bleaching events. These thermally tolerant genotypes are the foundation of the restoration program, chosen for their ability to withstand warming waters.

Underwater nurseries 

Branching coral fragments are suspended on underwater "tree" structures or rope lines for 8 to 10 months. Massive corals are fragmented using a diamond saw, mounted on ceramic plugs, and grown in nursery racks for around six months before outplanting.

Outplanting to the reef

Once large enough, corals are secured to the reef using a variety of methods. Branching corals are attached to Reef Stars, hexagonal metal frames that lift corals off the sediment-laden seafloor and provide 3D habitat structure. Massive corals are attached directly to the reef substrate.

Bleaching contingency planning

During marine heatwaves, the team responds in real time by lowering nursery structures to cooler depths, installing temporary shading devices to cover sensitive corals, and by suspending outplanting until thermal stress subsides.

3D monitoring through photogrammetry

Raising Coral uses Samsung Galaxy phones to take pictures of the reef underwater. These photos, taken with Samsung’s “Ocean Mode”, produce high quality images that are used to build 3D coral reef models. A time series of 3D models will track coral growth, reef habitat 3D structure, and biodiversity recovery. This visual evidence of restoration impact is shared with communities, scientists, and policymakers to drive restoration forward.

Community training and co-management

Local coral gardeners are trained through a comprehensive two-week program covering diving, restoration techniques, leadership, and first aid. They are compensated for their fieldwork and become long-term stewards of the reefs in their backyard.

A New Way to Fund Reef Restoration

This project issues Biodiversity Blocks, a type of marine biodiversity credit developed by Seatrees. When you purchase a Biodiversity Block, your funding goes beyond planting a coral: you are supporting a whole group of actions that go with restoration to help make it effective: long-term monitoring, community engagement and training, bleaching contingency planning, restoration research, and annual reporting. Each Block represents one coral planted, plus all the stewardship work that surrounds it.

Built for transparency

  • This project follows the Seatrees Crediting Protocol for Marine Restoration v3.2, a peer-reviewed scientific framework for designing, implementing, and monitoring community-led marine restoration projects. 
  • Donors can track the impact of their investment through a real-time donor dashboard
  • The project publishes annual monitoring reports that document ecological and social outcomes over the full five-year project period.

What the science says

Before any corals were planted, Seatrees and Raising Coral conducted a comprehensive Baseline Assessment across Golfo Dulce and Caño Island. Drawing on 45 years of scientific data and new 3D photogrammetry surveys, the assessment established a Biodiversity Spectrum for six key metrics spanning ecosystem structure, composition, and function. Based on this analysis, the project is targeting a 34% average biodiversity uplift across both locations over the five-year project period.

Want to dig into the details?

The full Project Description Document is publicly available and covers everything from the restoration plan and risk assessment to the biodiversity uplift calculations and approach to stakeholder engagement. It has been certified by two independent validators and represents the most complete account of how this project operates.

A Reef Full of Life

The reefs of the Osa Peninsula support an exceptional range of marine biodiversity. The project directly benefits coral species being outplanted, threatened reef fish, and charismatic megafauna that depend on healthy reef structure.

Species present at the project sites include:

  • Porites, Pavona, Pocillopora, and Psammocora corals, several of which are directly outplanted
  • Over 200 reef fish species at Caño Island, including commercially important snappers, jacks, grunts, groupers, and parrotfish
  • Green and hawksbill sea turtles
  • Whitetip reef sharks, whale sharks, and scalloped hammerhead sharks
  • Humpback whales, two populations of which use Golfo Dulce for several months each year
  • Green spiny lobster and endangered brown sea cucumbers
4,000
corals outplanted 
10+
permanent monitoring sites with annual 3D photogrammetry surveys
8+
trained, compensated coral gardeners employed locally
5
years of biodiversity monitoring 
about our project partners

Raising Coral

Raising Coral is a Costa Rican nonprofit dedicated to the restoration of coral reefs in Costa Rica. Their team works to improve the resilience of reef ecosystems that are essential to marine life, local fisheries, tourism, and coastal communities.

Raising Coral began piloting coral propagation in Golfo Dulce in 2016 as part of a collaboration with the University of Costa Rica, representing one of the first major reef restoration projects on the Pacific Coast of Central America. Since then, they have installed 16 nurseries and outplanted more than 6,000 corals across Golfo Dulce. They recently expanded their work to Caño Island in 2025.

Raising Coral’s approach is grounded in the belief that restoration only works when centered around local communities. Through their coral gardener program, Coralmanía community outplanting events, school presentations, and environmental festivals, Raising Coral has built a growing movement of local reef stewards in the communities surrounding Golfo Dulce and the Osa Peninsula.

Learn More

Quality Education

Coral gardener training and community presentations build ocean literacy and technical skills for local residents and youth.

Gender Equality

Raising Coral’s team is currently more than 50% women and is expanding this goal to include local youth.

Decent Work and Economic Growth

Coral gardeners and boat captains are compensated for their fieldwork, strengthening the direct economic link between healthy reefs and local livelihoods.

Climate Action

The project uses climate-smart restoration strategies, including bleaching contingency plans and thermally tolerant coral selection, to build reef resilience to marine heatwaves.

Life Below Water

The core mission of the project is the active restoration and long-term monitoring of coral reef ecosystems in Costa Rica, supported by rigorous science and community stewardship.