Invasive Hydrilla Overruns Ciénaga Grande Wetland

In Colombia's Ciénaga Grande de Santa Marta, a vast coastal wetland on the Caribbean coast near Santa Marta, an invasive aquatic plant has rapidly overrun waterways over the past year, severely disrupting fishing communities that depend on the ecosystem for their survival.

The plant, Hydrilla verticillata, native to Asia and known locally as horse tail, first appeared around mid-2025 and now forms dense, carpetlike mats across large areas of the 428,000-hectare (1,600-square-mile) lagoon system, a UNESCO biosphere reserve since 2000. Its long strands extend deep underwater with roots anchoring to the lagoon bed, making removal challenging. In stilt-built fishing villages like Nueva Venecia, home to about 4,500 residents in 500 houses founded in 1847, and Buenavista, with 1,150 people in 163 homes established in the 1950s, open water has largely vanished. Residents navigate by canoe or small boat between homes, schools and shops, but the vegetation now chokes routes, tangles fishing nets and blocks access to freshwater collection points.

"What we're seeing here today is a problem. One that affects not only movement or fishing, but the community as a whole," said Jhon Cantillo, a...