The National System of Conservation Areas (SINAC) has officially convened a special technical commission to conduct an urgent assessment of potential environmental damages to the Térraba-Sierpe National Wetland (HNTS). This action is in response to significant concerns over a proposed solid waste treatment facility (landfill) in Salamá de Osa, Puntarenas.
The review is focused on the project’s potential to critically disrupt the hydrological integrity and biodiversity of Costa Rica’s largest Pacific mangrove ecosystem, a designated Ramsar Site of international importance.
The Primary Threat: Hydrogeological Contamination
The commission’s primary mandate is to evaluate the hydrogeological risks posed by the proposed landfill, operated by the company Nova Tierra Energy Costa Rica.
The principal scientific concern is the high probability of leachate infiltration. Leachate, a highly toxic effluent formed as water percolates through decomposing solid waste, contains a hazardous cocktail of heavy metals (such as lead and mercury), ammonia, and persistent organic pollutants.
The project is located in the wetland’s catchment area, raising critical concerns that these contaminants could infiltrate the subterranean aquifers. These aquifers are the primary hydrological feed for the HNTS. An infiltration event would introduce high-toxicity pollutants directly into the sensitive aquatic system, threatening the foundation of its trophic web.
This threat is considered severe enough that in January 2025, the National Environmental Technical Secretariat (SETENA) issued a precautionary measure, suspending the project’s environmental viability pending further investigation into its hydrological impacts.
Ecosystem Profile: The Biological Significance of HNTS
The Térraba-Sierpe National Wetland, designated Ramsar Site #782 in 1995, is a hotspot of neotropical biodiversity. Its ecological importance cannot be overstated:
- Mangrove Forest Dominance: It constitutes the most extensive and best-preserved mangrove forest on Costa Rica’s Pacific coast. This ecosystem, dominated by species like the Red Mangrove (Rhizophora mangle), is a vital habitat.
- Critical Nursery Function: The intricate sub-aquatic root systems of the mangroves serve as a critical nursery and feeding ground for juvenile populations of countless marine species. This includes commercially vital fish, crustaceans, and mollusks like the Anadara tuberculosa (mangrove cockle), which sustains local artisanal economies.
- Avian and Mammal Sanctuary: The wetland provides a crucial habitat and stopover point for hundreds of resident and migratory bird species, as well as mammals adapted to this unique deltaic environment.
- Ecosystem Services: The HNTS provides irreplaceable ecosystem services, including acting as a biological buffer against storm surges, trapping sediment, and serving as a massive “blue carbon” sink, sequestering vast amounts of atmospheric carbon.
A System Under Cumulative Stress
The SINAC commission’s assessment arrives at a time when the HNTS is already under severe, multi-faceted environmental pressure. The proposed landfill is not an isolated threat but a cumulative stressor on a strained ecosystem.
Existing threats include:
- Non-Point Source Pollution: Decades of persistent agrochemical runoff from upstream pineapple and palm oil plantations. This has led to documented nutrient loading (eutrophication) from fertilizers and contamination from pesticide residues, degrading water quality.
- Illegal Land Use Change: Illegal occupation within the protected area’s boundaries for extensive cattle ranching and rice cultivation. This fragmentation involves illegal logging, land filling, and the construction of drainage canals, which fundamentally alters the local hydrology and increases sedimentation.
- Unsustainable Exploitation: The prevalence of illegal gillnet fishing (“trasmallos”) disrupts the reproductive cycles of marine fauna, threatening to collapse the very populations the wetland is meant to protect.
The SINAC commission is now tasked with determining if this already-vulnerable ecosystem can withstand the additional, high-stakes threat of a regional landfill. Their findings will be critical in deciding the future ecological integrity of one of Costa Rica’s most valuable and irreplaceable biological assets.
