Satellite monitoring finds more than 500 oil spills across the Gulf since the war began

Experts warn the damage to Gulf ecosystems could last decades

The vast, dark slicks in the strait of Hormuz are visible from space. More than 500 oil spills have polluted the Gulf, the Strait of Hormuz and the Arabian Sea since the war between the United States and Iran began on 28 February, according to satellite monitoring by Greenpeace. The environmental group’s findings include major spills linked to attacks on vessels, as well as slicks detected around the time of strikes whose origins could not be confirmed.

Throughout October, oil tankers were struck by missiles or sea mines in the waterway and spilled crude into the sea. The pollution has spread across the Gulf, contaminating coastlines and threatening to cause lasting damage to marine ecosystems that are home to dolphins, sea turtles and countless species of fish. Greenpeace has counted more than 133 attacks on oil tankers since the conflict began. October was the worst month, with more than 30 confirmed or reported attacks in the Strait of Hormuz and surrounding waters, according to the Washington Institute for Near East Policy, and the attacks have continued into November.

Eight months into the fighting, the strait — the only maritime passage between the Gulf and the Arabian Sea and one of the world’s busiest oil shipping routes — has become a battlefield and the center of a growing environmental disaster. The naval blockade of the waterway has made documenting pollution from the ground almost impossible, so environmental experts and marine biologists have assembled their picture of the damage from satellite imagery.

The strait supports a rich but fragile marine environment of coral reefs, mangrove forests and seagrass meadows that sustain dolphins, sea turtles and countless species of fish. It plays a vital role in the circulation of water and nutrients and serves as a migration route for marine mammals. Even in peacetime, its ecosystems faced mounting pressure from shipping, oil extraction and coastal development. Oil can coat birds’ feathers, making it difficult for them to float and find food. Oil covering mangrove roots prevents the trees from absorbing oxygen and can potentially kill them.

Bernhard Riegl, a marine biologist at Nova Southeastern University in Florida who has studied the Gulf for more than 30 years, warned that the war could cause lasting damage to the Gulf’s confined waters, already under severe pressure from the climate crisis.

“Since the Gulf is shallow, and summer is the least windy period of the year, atmospheric heat is rapidly translated into ocean heat. That heat kills corals, algae, fishes. There is no cold, deep water that could mix and buffer this heat,” Riegl said. “Everybody knows that oil in water is not good. The potential for additional damage is significant. There is no such thing as a ‘clean war’. Not for the unlucky humans that are drawn into it, nor for the unlucky environment in which the conflict takes place.”

“Adding together the daily mapped footprints [of the spills] gives a cumulative total of approximately 20,000 square kilometres – almost the size of Wales,” said Nina Noelle, a Greenpeace expert on environmental disaster relief.

Among the most polluting of the October attacks was a strike on the supertanker Gem No 2 off the coast of the United Arab Emirates, which left a slick stretching more than 21 miles (35km). The Gem No 2 was photographed ablaze at sea. A satellite image dated 19 October shows a huge patch of black moving into the clear waters off the coast of Umm Al Quwain. Greenpeace estimates that an attack on a tanker in early June produced a slick off the coast of Oman that covered more than 600 sq km (230 sq miles) at its peak. Two Iranian naval vessels hit in March kept leaking oil for months, said Wim Zwijnenburg, an environmental researcher with the Dutch peace organization Pax, and an attack on the Liberian-flagged Minoan Pioneer on 3 August has also been linked to a major slick. The Minoan Pioneer was photographed off the coast of Muscat, Oman, on 30 October.

Oil pollution has reached several coastlines since the war began. In March, a slick from the Shahid Bagheri was detected near the Hara mangroves. In April, pollution threatened Shidvar Island, a protected area home to coral reefs, seabirds and turtles. Oil was reported washing ashore at Qeshm Island in August, near important fishing grounds and turtle nesting sites, and a photograph dated 13 August shows an oil slick along the southern coast of the island. Satellite imagery also shows slicks near Oman’s Musandam national park, home to coral reefs and seabird breeding grounds, and Iran’s Minab River delta, which has protected mudflats and mangrove forests. A satellite image showed an oil slick spreading off Kharg Island, a key oil export terminal for Iran, in May.

Oil has also washed up on Gulf beaches in recent weeks. Photographs show oil washing up on a beach in Umm Al Quwain, UAE, on 24 October and on a beach in Sharjah, United Arab Emirates, on 1 November, and workers cleaning a stretch of beach in Sharjah after oil washed ashore there on 3 November.

Establishing responsibility for the spills is not straightforward. Iran’s Islamic Revolutionary Guard Corps has been blamed for most of the attacks. US forces have also targeted tankers, disabling Iranian vessels attempting to cross a US naval blockade and striking others in response to Iranian missile attacks on US warships. According to a Wall Street Journal report, the largest oil spill was caused by a strike carried out by the UAE’s air force on oil storage tanks on Lavan Island. The strikes resulted in crude oil flushing into the Gulf and affecting coastal areas, including the nearby nature reserves of Shidvar Island.

Environmental organizations continue to analyze satellite imagery but warn that the full extent of the damage cannot be established without investigations on the ground, which remain extremely difficult. Some researchers and environmentalists contacted in Iran and Gulf states said they had been instructed by domestic authorities not to speak publicly about the environmental damage caused by the war.

In some instances, countries bordering the strait have responded to spills. After the Gem No 2 attack, the United Arab Emirates closed beaches, launched a major cleanup and monitored its desalination plants; authorities said on 30 October that the leak had been stopped and pollution was declining. In Oman, divers and equipment were deployed to a damaged vessel, and crews cleared oil from 7 miles of coastline near the Hallaniyat Islands.

The wider environmental damage may prove far harder to contain. Contamination can affect organisms ranging from small invertebrates to fish, birds and turtles. “Oil could remain trapped in sediments, shorelines and mangrove roots long after slicks disappear, damaging marine food chains and threatening coastal communities dependent on fishing,” Noelle said. “Mangroves and coral reefs can take decades to recover, particularly when oil persists in sediments,” she added. “Repeated spills, such as those in the strait of Hormuz, risk worsening the damage.”

The Gulf’s history offers evidence of how long such contamination can persist, Riegl said, pointing to the aftermath of the Iran-Iraq war of the 1980s and the first Gulf war, when tankers, loading facilities and oilfields were targeted. A 2020 study traced widespread deposits of tar – the thick, sticky residue left as crude oil breaks down – on Qatari beaches to the Gulf war. A 2022 study found sediment on Saudi Arabia’s Abu Ali Island still contaminated by oil from the 1983-85 Nowruz spills during the Iran-Iraq war, which collectively leaked 80 million gallons of crude into the sea.

“Any organism that has to dig into beaches [affected by spills], like sea turtles when they lay eggs, will encounter the contaminated strata and adverse effects can be expected. Burrowing organisms like ghost crabs will continue to bring contaminated material to the surface,” Riegl said. “Clearly, the effects of large-scale oil pollution remain detectable for decades – so this is a generational problem. We could really lose something irreplaceable.”