Caribbean & Central America - August 2025

Dead seaweed is accumulating on Caribbean beaches at a faster rate than ever before. It could pose a serious problem for the environment, fishing, and for tourism.

The authorities in Barbados, Mexico, and the Dominican Republic were cited by the international media as saying that hotel bookings are down this year by 30%-40% during the peak sargassum period (which typically runs between May and August). Beaches in Puerto Rico and Cuba are also among those affected. In Mexico, the Yucatán tourism business council (Cetur) says stopover hotel bookings are down as reports from the beaches speak of piles of brown seaweed, dead fish, and the smell of rotting algae. In June some schools near the coastline in Martinique were forced to close to protect children from increases in hydrogen sulphide and ammonia fumes coming from the seaweed. 

Speaking at the United Nations Ocean Conference in June, the Dominican Republic’s President Luis Abinader called for recognition of the environmental crisis posed by sargassum in the Caribbean, which he said could deliver “a significant blow to the GDP of island nations”.  

Sargassum is a type of seaweed found in the Sargasso Sea. Farah Nibbs, a marine science expert at the University of Maryland in the US, says that in normal times it is a “good thing” playing a positive role in the ocean eco-system. However, times are not normal. Since 2011 the seaweed blooms have been expanding dramatically. Brian Barnes, a research associate from the University of South Florida (USF) in the US was cited by British newspaper The Guardian as saying that “the peaks just seem to be getting bigger and bigger, year after year”. This is thought to be connected to global warming and increased nutrients from fertiliser run-off into the Atlantic carried by major rivers such as the Amazon and Mississippi.

A 31 July bulletin by the USF’s Optical Oceanography Lab calculates that in July there was 38m tonnes of the seaweed floating in the Caribbean and neighbouring parts of the Atlantic.

The economic impact is significant. A report published in May 2024 by the US National Oceanic and Atmospheric Administration (Noaa)’s National Centers for Coastal Ocean Science (NCCOS), a US government office, estimated that in Quintana Roo, Mexico, for example, sargassum cleanup efforts are estimated to cost as much as US$1.1m per km per year. Tourism is the number one industry and source of foreign exchange in many Caribbean countries (in the Dominican Republic it accounts for 16% of GDP). There are also important negative impacts on fishing and on the leisure boats sector (the seaweed clogs up propellers and moorings).

Governments and businesses are looking at ways of responding and cutting their losses. Yucatán’s state tourism board is promoting seven non-beach destinations in the state to try and retain visitors. UK-based aquaculture company Seafields, says it has developed a satellite-based system which can track the seaweed before it arrives onshore, allowing it to be captured and held in open-water paddocks, for potential use in biofuels and livestock feed. Meanwhile BioPlaster, a Mexican company, says it has developed a way of using sargassum as an alternative to cling-film and plastic bags. It is not yet clear whether such approaches will prove commercially viable, but pressure for solutions to the Caribbean’s “seaweed problem” is likely to increase.