Sargassum: a continuing challenge

By David Jessop

It was not to be. A ‘Sargassum Summit’ to develop a multinational response to the worsening problem of the sargassum seaweed washing up on some of the best beaches in the Caribbean, has had to be postponed.

The conference in Cancun, which has been delayed for domestic political reasons, is now expected to take place at a later date. Then Mexico’s Ministry of Foreign Affairs will bring together representatives from government, the private sector, and experts from the Caribbean, Central America and the US to discuss how best to respond to the effect that the environmental phenomena is having on tourism and fisheries, and its damaging economic consequences.

Sargassum, of course, is a type of abundant seaweed creating ocean rafts that stretch for miles. Although ecologically important and a floating habitat for multiple forms of marine life, when carried onshore by prevailing tides and winds it builds up in the form of a rotting mass of foul-smelling vegetation.

In the past it was largely believed to originate in the Sargasso Sea in the West Atlantic. More recently however, scientists believe that it has started to arrive in the Caribbean from the equatorial waters between Brazil and West Africa, where sea temperatures are rising as a result of climate change, and where pesticide and fertiliser runoff from the Amazon and Congo rivers is causing it to proliferate.

So serious has the problem become that a recent MIT Technology Review suggested that the cumulative effect is beginning to disrupt the equilibrium of coastal ecosystems and by killing off the seagrasses that help keep sand in place, is causing beaches to erode more rapidly.

There are indications that the Caribbean may again see this year unusually large amounts of sargassum seaweed washed up on its shores. In recent days large quantities have begun to arrive on Mexico’s south eastern Caribbean coast, with forecasters suggesting that as the year goes on the rest of the region may also suffer.

According to a report produced by the University of South Florida Optical Oceanography Lab, its satellite ocean mapping showed in April large amounts of sargassum across much of the Caribbean Sea except in the nearshore waters of Venezuela and Columbia, and in quantities higher than the historical record set in 2018 for the same month.

Its analysis suggested that this could mean that while ‘the exact sargassum amount, timing, and location of the beaching will depend on local ocean circulations and winds’ the volume in the Caribbean Sea in 2019 may be ‘comparable to or even higher than in, a historical record’.


Although sargassum has been arriving in the Caribbean for many years, its mass has now become so great that voluntary efforts to clean beaches are proving ineffective, with potentially longer term negative economic consequences for tourism in particular.

Tourism Ministers and industry representatives indicate they have become increasingly concerned about the seaweed’s unsightly appearance, visitor complaints, the cost of mechanical removal, and the possibility of reputational damage. There is also some anecdotal evidence of investors questioning the long-term cost implications in relation to projects they are engaged in.

To try to address the issue, the University of the West Indies and a number of other regional and international bodies have been exploring possible solutions including industrial or nutritional uses for the seaweed if processed, issues related to the ecological damage to beaches caused by the use of heavy machinery to clear the sargassum, and what if any technical solutions there may be to keep the seaweed offshore.

One suggestion is that the seaweed should be harvested. A United Nations Environment Programme (UNEP) white paper published in October 2018 indicated a variety of uses including as fertiliser, as an input for nutraceuticals, or for biomass, biogas or other purposes.

Although some enterprises have begun to take advantage of sargassum in this way, for example in St Lucia for fertiliser, sustainability paradoxically is an issue, as there is no guarantee that the seaweed will always be available onshore in the required quantities.

An alternative but costly defensive solution being considered by several countries in the region is the installation of barriers. These, it is suggested, might keep the seaweed from reaching the shore in a manner that will result in the ocean currents then carrying the sargassum back out to sea.

In addition, the Caribbean Regional Fisheries Mechanism announced earlier this year that it had begun a fact-finding study and why in some years such as 2018 it had reached unprecedented levels with an estimated clean-up cost of US$120m. The survey, funded by the Japan International Cooperation Agency, is expected to suggest actions for the regions fisheries and tourism industry and the scope of support that Japan may provide to help address the problem.

If the problem of sargassum does occur again this year in the same way as it did in 2018 it will also require clear and sustained visitor messaging by the industry and governments, indicating that such inundations are sporadic, do not affect all beaches and there is much more for a visitor to do.

As the oceans warm, the Sargassum problem may well become more severe, suggesting that a regional technical response will be required and an understanding of who will meet the likely cost of clean-up operations and the development of longer-term responses. Above all, and as the delayed Cancun conference agenda suggests, what is now essential is a joined-up approach to yet another environmental issue that has long term economic and ecological implications for the whole region.


David Jessop is a consultant to the Caribbean Council and can be contacted at