Costa Rican pesticides kill fish in Madre de Dios lagoon

Environmental groups have reported a second case of fish poisoning in two weeks at Laguna Santa Marta and Laguna Madre de Dios on the Pacuare River in Batana, Limón, Costa Rica. The contamination was allegedly caused by nematicides applied to nearby banana plantations during the rainy season, without considering the potential environmental impact as rain increases runoff into the river ecosystem.

Laguna Madre de Dios (LMD) is a complex estuarine system on the Caribbean coast of Costa Rica that is rich in biodiversity, with species important for both local fisheries and commercial consumption. This includes endangered species such as the manatee. The lagoon is located near large monoculture pineapple and banana plantations, which increases the risk of agricultural runoff.

Research by the Regional Institute for the Study of Toxic Substances (IRET-UNA) confirms that pesticides from neighboring agricultural lands are carried by runoff into the tributaries of the lagoon, which leads to the presence of highly toxic pesticides and agrochemicals in the lagoon waters. This ongoing pollution is associated with significant fish kills, affecting the local ecosystem and the surrounding communities that depend on it.

Officials from the Office of Forensic Investigations (OIJ) and the Coast Guard documented the incident, collecting samples of the dead fish to assess toxicity levels.

Previous cases of infection

In 2003, thousands of fish and other aquatic life, including species such as eel, snook, guapotes, mojarra and macaque, died due to similar pollution. After this incident, multinational Standard Fruit Co. reached a settlement with the environmental administrative court, paying $8,000 a year for five years to repopulate the Pacuare River. However, the environmental assessment concluded that full recovery would take five years for fisheries and four years for tourism.

The pollution of these waters has had serious ecological consequences, including mass fish kills and loss of biodiversity. Communities near the Madre de Dios Lagoon are among the hardest hit, with about 100 families depending on tourism, fishing and coconut production as their main sources of income. These families rely on the health of the lagoon for sustainable tourism and environmental conservation.