World’s worst hotspot for oil pollution by ships

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In early February, a major oil slick appeared about 60km off the coast of Bintan, a northern Indonesia island near Singapore and popular with western and Asian tourists.

The ribbon of black sludge was 185km long, more than the distance from London to Birmingham, and almost 2km across at its widest point. It trailed a ship in such a way that it appeared to be the result of intentional dumping.

The oil slick was one of more than 2,700 identified globally by researchers over the past three years that emanated from passing vessels, using satellite imagery and artificial intelligence to track the pollution.

Until recently, little was understood outside the shipping world about the extent of the dumping as it is almost impossible to monitor comprehensively.

About 500 of the incidents were located in the waters of Indonesia, making the archipelago by far the worst affected by shipping oil slicks. The country’s territorial waters are only the sixth largest globally but play host to some of the busiest shipping lanes.

There are a number of ways in which vessels accumulate oil-contaminated waste. Cheap fuel is filtered before being fed into engines, resulting in the remaining sludge, or oil leaking from an engine can build up in the hull. Oil tankers may also wash cargo tanks between loads, or fill empty ones for ballast, producing oily water that needs disposal.

Since 1983 an International Maritime Organization convention prohibits vessels from releasing any liquid into the sea containing more than 15 parts per million of oil, and they must pay to offload anything else at ports with special disposal equipment.

Retired US coastguard Rear Admiral Fred Kenney, former legal director of the IMO, said the convention had led to a “massive improvement” in many regions but the slicks occurring today were partly because some coastal states did not have the resources or capacity to enforce the rules.

The flag state, where a vessel is registered, is responsible for enforcement, he said, but it also relied on the coastal state, the one where the slick occurs, to monitor pollution in its seas and report it.

“If unscrupulous ships’ crews and owners think they can get away with dumping oil in certain parts of the world they’ll do it,” Kenney said.

Chart showing countries which exclusive economic zones are hotspots for oil slicks, as identified by Sentinel-1 Satellite July 2020 to May 2023

Satellite and computer modelling technology is helping to identify those responsible for the pollution that remains “chronic” in some parts of the world, said John Amos, the chief executive of SkyTruth, a non-profit organisation that analysed the data provided by government satellites and private company partnerships. “Up until now this problem has been really well hidden,” he said.

Even so, the data likely only represents a small proportion of the problem, based on a 15 per cent sample of available global satellite images that were scanned and SkyTruth researchers then reviewed. The images are taken every six to 12 days and do not cover the entirety of the world’s oceans.

Sentinel-1 satellite images showing four oil slicks in south-east Asian waters. Captured between 2021 and 2022.

For 40 of the slicks tracked in south-east Asia, SkyTruth identified a registration number for the most likely responsible vessel. A search of a global registry by the Financial Times found that most were flagged to south-east Asian countries and six were Panama-registered. The Panamanian Maritime Authority did not respond to inquiries.

For three of the vessel numbers identified, the vessel owner was listed as Pertamina, the shipping arm of Indonesia’s state-owned oil company. Pertamina did not respond to a request for comment.

Indonesian researchers highlighted in a 2022 paper how picturesque Bintan, nestled in a busy shipping lane a short distance from Singapore’s major port, was particularly badly affected by the black sludge. Fishing communities were disrupted and tourist numbers declined, it said, though the extent was obscured by the coronavirus pandemic.

Amos said his organisation’s computer model, which scans thousands of satellite images for patterns to detect the slicks, would make it easier to track in real time those responsible in future.

At present, it was problematic that the publicly available satellite imagery that it relies upon does not cover the high seas, leaving those critical areas uncovered for bad actors to treat as a dumping area.

But a treaty signed last year by governments around the world to establish marine protected areas in the high seas meant “people are going to start wondering what’s happening out there”, he said.