Costa Rica rehabilitates mangroves in the Gulf of Nicoya

• Following a nationwide project, the country succeeded in rehabilitating mangrove areas that had been used for sugarcane cultivation and shrimp and salt farming.

October 11, 2022. Studies on mangrove loss revealed that in the Estero Puntarenas National Wildlife Refuge in Costa Rica, between 1945 and 2005, mangrove cover decreased by 766 hectares. The mangroves were affected mainly due to the expansion of small and large-scale agricultural activities such as sugar cane cultivation, shrimp farming, and salt mining, as well as urban development encroachment.

Given this scenario, experts set out to identify potential sites for rehabilitation in sugarcane fields and abandoned shrimp and salt ponds, using satellite images and drone images. In addition, previous studies of micro topography, historical water network, floristic composition, soil compaction, physicochemical variables of interstitial water, carbon content and social context of the reference sites and rehabilitation areas were carried out.

Based on the baseline information, rehabilitation plans were designed and prepared for each site and their subsequent implementation in the field. The plans included the intervention actions of opening canals or walls, dredging and cleaning of canals, vegetation cutting, according to the conditions of each site.

In the sugarcane cultivation areas, 155 hectares were rehabilitated by opening canals with machinery (16.7 linear kilometers) and manually opening mangrove canals (2.5 linear kilometers) to allow the tide to enter. The canals currently in place show the colonization of Avicenniagerminans and Laguncularia racemosa seedlings, as well as the presence of mangrove-associated fauna such as crabs, fish, and shrimp, among others. Avicennia germinans and Laguncularia racemosa, así como presencia de fauna asociada al manglar como cangrejos, peces, camarones, entre otros.

In the shrimp and salt ponds area, the conditions of 145 hectares of ponds were rehabilitated by channeling 3.49 km, clearing 2.80 km and demolishing walls at 19 points. As a result of these actions, there has been an improvement in the hydro period and soil structure.

This project involved the government (National System of Conservation Areas – SINAC, its Spanish acronym), international non-governmental organizations such as the Tropical Agricultural Research and Higher Education Center (CATIE) and Conservation International (CI), as well as private enterprise. The project was carried out with the financial support of the Pure Land Foundation.

"The project demonstrated that it is possible to carry out mangrove rehabilitation of these scales in the country with the collaboration of different actors," said Lenin Corrales, an expert from CATIE's Climate Action Unit.

According to Corrales, the rehabilitation of mangroves not only allows the recovery of important marine habitats, where fish that will later be part of the fishing activity of thousands of families are raised, but they are also an important carbon reservoir, thus contributing to the mitigation of climate change.

The project has been a basis for increasing knowledge about mangrove ecological rehabilitation processes and CATIE is currently developing a similar project in the Dominican Republic, where it is working on the restoration of 600 hectares together with Dominican government entities and local organizations.