Every year 1.2 billion tonnes of oil cross the seas in tankers. Since navigation is a human endeavour, there will always be human error. Oil spills are an utterly predictable cost of doing business, but is unpredictable in its social and environmental impact. Tourism and recreational activities are badly affected after an oil spill. Reduced catches of commercially exploited fish and shellfish are often reported after an oil spill. Industries that rely on seawater for their normal operation (eg. power stations and desalination plants) can be seriously disrupted, as may be other coastal industries such as shipyards and harbours

Lethal concentrations of toxic components are relatively rare, localized and short-lived and are associated with spills of light refined products and fresh crude; animals and plants at risk are those living in areas of poor water exchange and in other situations where high concentrations of toxic components persist for longer periods. Sedentary animals in shallow waters such as oysters, mussels and clams that routinely filter large volumes of seawater to extract food are especially susceptible to bio-accumulation of hydrocarbon components of oil spills

The main threat posed to living creatures is one of physical smothering by the persistent residues of spilled oils and water-in-oil emulsions, leading to death through the prevention of feeding, respiration and movement. As damage is caused by physical contact, marine life most at risk are marine mammals, reptiles and plants living close to shorelines, birds that feed by diving or flock at on the sea and plant and animals in aquaculture facilities and storage pens in tidal areas

Coral reefs are at risk if they are directly exposed to floating oil during extreme tides or to high concentrations of dispersed oil. Rocky and coarse sand shorelines, exposed to wave action tend to self-clean rather rapidly, whereas fine sand and mud shorelines in sheltered areas soak up oil, which that then persist for decades. Saltmarshes and mangrove areas can take one to several decades to recover from a single oiling

When the oil market crashed in 1973, dozens of tankers were laid up. Some were well looked after but others were badly maintained and cost owner millions to restore when the ma Accidents have increased because of corner-cutting driven by slumping revenues in 1980s. As crude oil prices crashed from $40 a barrel in 1981 to as low as $10 a barrel five years later, the industry hacked spending, reduced tanker crews, hired cheaper and fewer sailors, and begun to stretch equipment, delayed maintenance and repairs. When the market expanded again in the mid-1980s, it cost owners millions to restore the badly maintained tankers. New tankers built during the oil boom of the mid-80s were of inferior materials and contained 10% less steel and when they hit the ground they do not have the strength to take the impact. Still the majority of large tankers are out of date, over-age and often poorly maintained. Lloyds Register recorded that most carriers in 1990 were 10 years old or more, with the heavier supertankers 15 to 20 years old

Between 1980 and 1990 there were 435 recorded oil spills of over 50 barrels. The average amount of oil spilled annually from tankers is now approaching 1.5 million tons. The wreck of the Amoco Cadiz supertanker in March 1978 spilled over 1.5 million barrels of crude oil and fouled more than 160 kilometres of shoreline. This ruined the annual harvest of oysters, lobsters, fish and seaweed, and caused some one million or more tourists to avoid the Brittany coast. Damages of $140 million were set in 1988, $105 million of which was directed to the French national government, local governments and businesses. In 1988 the explosion and subsequent burning of the Piper Alpha drilling platform in the North Sea killed 170 people. More than 170,000 gallons of petroleum fuels escaped the Bahia Paraiso, an Argentine Navy supply ship, after it ran aground in January 1989 threatening wildlife in the Bismarck Strait of the Antarctic Peninsula. The Exxon Valdez ran aground in March of 1989 spilling 40 million litres of oil into Prince William Sound, one of the most bountiful marine ecosystems in the world, spreading over 3,000 square km of water and fouling 1,600 km of shoreline

Texaco dumped some 4.3 million gallons per day of toxic oil waste water over a period of 20 years previous to 1999, in the Ecuadorean rainforest. The equivalent of three Exxon Valdez oil disasters. It is claimed that Texaco left behind 300 open waste pits contaminated with heavy metals and carcinogenic hydrocarbon compounds. It is estimated that Texaco saved $3 to $4 per barrel - close to $6 billion over 20 years in additional profits - by dumping the waste water rather than pumping it back beneath the earth's surface. Oil spills along the company's Trans-Ecuadorean Pipeline totaled an estimated 16.8 million gallons. Damages caused by Texaco's practices are estimated to be in excess of $1 billion

On the 17/5/1999, thousands of barrels of oil spilled into the Peruvian Amazon rainforest after heavy rains triggered a landslide which broke the country's largest oil pipeline. The landslide wiped out 13 feet (four meters) of the 530-mile (850-km) pipeline owned by the state oil company, Petro-Peru. It was reported that the spill dumped 12,500 barrels of oil in the ecologically sensitive area

It is conservatively estimated that the Niger Delta experiences about 300 separate oil spillages every year. Occurring from old worn- out flowlines which traverse several kilometers of mangroves and swamps through which oil companies transport crude oil from the scattered oil fields to their oil export terminals