After a Japanese-owned oil tanker struck a reef off Mauritius on July 25, a prolonged period of inaction is threatening to become an ecological disaster.

Carrying nearly 4,000 metric tons of fuel oil, the tanker ran aground near Pointe d’Esny on the island in the Indian Ocean. “Local authorities failed to do enough to prevent what is now the worst ecological disaster in Mauritius,” blogger Ish Sookun wrote in a post on August 8. “They started putting buoys and barriers to protect the shore only after the first signs of the oil spill became apparent.”

By Tuesday, over two weeks after the accident, more than 1,000 tons of fuel had leaked from a crack in the vessel’s hull, with the Mauritius government declaring a state of environmental emergency.

French President Emmanuel Macron responded to calls for international help, sending military aircraft from the neighboring island of Reunion carrying pollution-control equipment and a naval vessel carrying booms and absorbents. According to Mitsui OSK Lines, the company that owns the vessel, some 1,000 tons of oil have been recovered from the ship, and a further 500 from the water. Around 1,500 tons remain on board. “Thousands of species around the pristine lagoons of Blue Bay, Pointe d’Esny and Mahebourg are at risk of drowning in a sea of pollution, with dire consequences for Mauritius’ economy, food security and health,” said Greenpeace in a statement. The community has taken matters into its own hands, with hundreds of volunteers building sugar cane pulp buoys and placing them in the water “to try to absorb and contain the oil which had already spread in our lagoons,” Sookun reported.

“Booms are made of nylon mesh filled with #sugarcane straws all hand-stitched by Mauritian volunteers, empty plastic bottles used as buoys,” described Mauritian journalist Zeenat Hansrod in a tweet.

The method for tackling oil spills depends on several factors, including the type and amount of oil in question, location and weather conditions. “Once the oil comes to shore, the more intensive the cleaning technique. You can risk causing further damage,” said Nicky Cariglia, an independent consultant at Marittima, who specializes in marine pollution. “If you wanted to remove all traces of oil, the techniques available become increasingly aggressive the less oil that remains. In mangroves, you would have the added risk of causing damage by trampling,” Cariglia told DW. Highly sensitive mangrove ecosystems line the Mauritius east coast that is threatened by the current spill.

Because oil normally has a lower density than water, it floats on the surface of the ocean. This means that for clean-up action to be most effective, it should happen very quickly after a spill, before the oil disperses. One method of controlling oil spills at sea, which was used after the Grande America cargo vessel sank in March 2019 some 300 kilometres (186 miles) off the French coast, is essentially scooping up the oil from the water’s surface. This is done using so-called booms, which act like a barrier to prevent the oil from spreading. Once it’s contained, boats equipped with so-called skimmer machines can suck up the oil and separate it from the water. After being processed, the oil can even be re-used. It seems like a simple method, but it only works when the oil is in one place — and under the right conditions.