20,000 sq km of oil slicks: Gulf war leaves decades-long toxic legacy

Satellite imagery has identified a cumulative oil slick footprint of approximately 20,000 square kilometres across the Gulf, Strait of Hormuz and Arabian Sea since the US-Iran war began on February 28, according to Greenpeace. That is an area roughly the size of Slovenia, spread across some of the world's busiest tanker lanes.

Greenpeace has logged 540 possible oil spills in that window. The organisation itself cautions that not all detections have been conclusively linked to attacks on shipping — a caveat that matters when raw satellite counts drive headlines.

The spills continue daily, with many more strikes on ships reported every week. The commercial consequences for tanker owners, insurers and charterers are compounding with each incident.

How bad is the damage?

The environmental consequences could last for decades, and there is a precedent with hard numbers behind it. A 2022 study published in the Journal of Marine Science and Engineering found extensive oil deposits along more than 25 km of Saudi Arabia's Abu Ali Island coastline — almost 40 years after the Nowruz oil spills of 1983–85, which occurred during the Iran-Iraq war.

Researchers found oil contamination in 76% of 1,434 test pits dug along that coastline. In other words, three out of every four sampling points still showed petroleum residues nearly four decades after the surface slicks disappeared. Any suggestion that today's slicks will dissipate quickly sits uneasily against that record.

What happened this week?

The past 48 hours illustrate the pace of escalation:

• Iran claims four oil tankers struck naval mines in the Strait of Hormuz over two days.
• A separately confirmed attack on a Sinokor-operated tanker off the UAE forced the evacuation of 22 seafarers.
• The International Maritime Organization (IMO) counts 134 confirmed Hormuz strikes through November 11, with 25 seafarers killed since the conflict began in late February.

Iran's Revolutionary Guards Navy claimed yesterday that two supertankers carrying more than 4 million barrels of oil between them were disabled by explosions on Wednesday. Tehran said the vessels had ignored warnings against using what it described as an unauthorised route through the strait. Iranian state media attributed the blasts to naval mines and broadcast footage purporting to show the incidents — footage that has not been independently verified.

The Iranian army subsequently claimed that another two tankers struck mines in the eastern part of the strait on Thursday afternoon, again after ignoring navigation warnings and switching off their radar systems. None of the four vessels has been identified. None of the claims has been independently verified. That gap between assertion and confirmation is now a defining feature of this conflict's information flow.

Was the UAE attack confirmed?

Yes — and it is the most documented incident of the week. UK Maritime Trade Operations (UKMTO) confirmed that a tanker was struck by an unidentified projectile 14 nautical miles northwest of Ras Al Khaimah, UAE, at 1800 GMT on Wednesday. The projectile hit the vessel's engine room, starting a fire and forcing the evacuation of its crew.

India's shipping minister Sarbananda Sonowal subsequently identified the vessel as the Liberia-flagged Dominica Prosperity. He reported that all 22 crew members — 19 of them Indian nationals — were safely evacuated. The tanker was drifting off Mina Saqr at the time of the attack.

For shipowners and crews transiting Hormuz, the pattern is grim but consistent: mines in the strait, projectiles off the UAE coast, and an official toll — 134 strikes, 25 dead — that lags a war still generating incidents weekly.

Unless mine strikes and projectile attacks subside, the slick footprint Greenpeace measured at 20,000 square km will keep growing, and the Abu Ali precedent suggests the cleanup bill will outlast the conflict by decades.