thumb|369x369px|Map of the Persian Gulf and the countries around it
The Gulf War oil spill (or Persian Gulf oil spill) was the second largest oil spill in history, resulting from the Persian Gulf War in 1991. Iraqi forces allegedly began dumping oil into the Persian Gulf in January 1991 to stop a U.S. coalition-led water landing on their shores. Despite quite high initial estimates, the amount of oil spilled was likely about 4,000,000 US barrels (480,000 m<sup>3</sup>). In the months following the spill, most clean-up was targeted at recovering oil, and very little clean-up was done on Saudi Arabia’s highly affected beaches. An initial study in 1993 found that the spill will not have long-term environmental consequences, but many studies since 1991 have concluded the opposite, claiming that the spill is responsible for environmental damage to coastline sediments and marine species and ecosystems.
The spill
At the end of January 1991, Iraq began to deliberately spill massive amounts of oil into the Persian Gulf, in an apparent attempt to foil a potential landing by US Marines on Kuwait's coast. It also made commandeering oil reserves dangerous for US and Coalition forces as visibility and movement were inhibited. Joyner and Kirkhope also posit that the spill could have been an attempt by Iraqi forces to cut off important water supplies for Coalition forces in Saudi Arabia.
Coalition forces determined the main source of oil to be the Sea Island Oil Terminal in Kuwait, which spilled approximately 70,000 to 80,000 tons of oil each day for a week. On January 27, four US F-111 fighter-bombers destroyed pipelines to prevent further spillage into the Persian Gulf. Several other sources of oil were found to be active: tankers and a damaged Kuwaiti oil refinery near Mina Al Ahmadi, tankers near Bubiyan Island, and Iraq's Mina Al Bakr terminal.
Early estimates from the Pentagon on the volume spilled hovered around . These numbers were significantly adjusted downward by later, more-detailed studies; government researchers placed the volume of oil spilled between and , while private researchers placed it between and .
The slick reached a maximum size of by and was 5 inches (13 cm) thick in some areas. Despite the uncertainty surrounding the size of the spill, figures place it several times the size (by volume) of the Exxon Valdez oil spill, making it one of the—if not the—largest oil spills in history. In a Wall Street Journal article written 14 months after the spill, Ken Wells reported that an estimated 375 miles (604 km) of shoreline remained covered in oil. Linden and Husain similarly estimated in 2002 that about 30-40% of the oil was removed by evaporation. Linden and Husain found that in 2002, on average, oil penetrated about 10 cm, but in some circumstances, oil penetrated almost 50 cm, a depth that lengthens the natural degradation process significantly. In 2017, Joydas et al. concluded that, while open water areas had low concentrations of hydrocarbons in the sediment, secluded bay areas had “alarming levels” that threatened the quality of life of organisms in such areas.
Researchers have focused on the health of the unique habitats of the Persian Gulf, including coral reefs, salt marshes, mud flats, and mangrove forests (Booth). Some researchers found that marshlands and mud tidal flats continued to contain large quantities of oil, over nine years later, and full recovery is likely to take decades. In 2001, German geographer Dr. Hans-Jörg Barth found that salt marshes still suffered significantly from the spill while rocky shores and mangroves showed a full recovery. He attributes the delayed recovery of the salt marshes to the lack of wave action/physical energy and oxygen in the environment, important factors to the natural degradation of oil. Issa and Vempatti also found that mangrove forests had mostly recovered by 1995.
Linden and Husain in 2002, as well as Issa and Vempatti in 2018, reported that the oil had largely lost its toxicity by the time it reached shore; however, the oil coated vegetation and blocked light and air, damaging it.