Oil Spills: The impact on the marine environment - Riskaware

Oil Spills: The impact on the marine environment

“ITOPF estimated that between 1970 and 2016 approximately 5.73 million tonnes of oil were lost as a result of tanker incidents” – Our World in Data

The general global trend shows tanker oil spill incidents on the decrease, averaging roughly 1.8 large spills per year. Nevertheless, there are still hundreds of tonnes of oil entering our ocean from each spill.

In 2018, the ITOPF recorded two large spills (greater than 700 tonnes) and three medium spills (7 to 700 tonnes) globally. And smaller oil spills are still an extremely prevalent threat. In the U.S. alone, in that same year, there were 137 confirmed or potential smaller spills.

Despite the positive message that these incidents are becoming less common – the scale of the potential impacts from even one spill shouldn’t be overlooked.

What are the causes of oil spills in water?

Oil spills can occur naturally, through oil leakage points or “seeps”. This is when crude oil enters water bodies through cracks or fractures in the ocean floor.

But, due to the relatively small amounts of oil released, these natural sources are not nearly as impactful on the state of our oceans and our coastlines as oil spill incidents caused by humans. Two of the primary contributors to oil-related incidents are wellhead blowouts, such as the Deepwater Horizon disaster, and tanker spills, like the Exxon Valdez.

Although events caused by human activity may be relatively less frequent than natural oil leakage, they can have much more widespread and dramatic consequences.

What are the potential effects of oil spills?

Oil spills can have profound and devastating impacts, many of which permeate long after the spill incident itself has occurred. Many consequences can be felt immediately – such as oil soaking wildlife and coastlines – but many are equally insidious and complex – such as the direct and indirect influences on the economy and public health long-term.


Both marine and land habitats and animal populations can be affected by an oil spill. Birds, fish, and other sea life can be harmed if not killed by oil. For example, they may be coated in oil, which impacts their ability to move, thermoregulate and eat, or become trapped in oil slicks completely.

These impacts on wildlife can be seen long after an oil spill, in some cases even affecting the new generation of the population.


Oil spills can impact oceans, coastlines, rivers, seabeds and much more. Oil has the potential to destroy habitats, particularly those that are sensitive or protected such as mangroves or coral reefs, and disrupt the natural ecosystems that make up these environments.


From fishing industries to agriculture, the local business economy may feel the effects of both physical damage and limitations for many years after an oil spill. Many people could lose their income and/or their livelihoods.

Whilst fines placed on the parties responsible can help compensate governments and local communities impacted by a spill, they are unlikely to cover the large immediate cost to the economy.


Tourist destinations, and therefore businesses that take advantage of these areas, are often directly impacted by oil spills as a consequence of oil washing up on beaches or hitting the coast. There is also a more intangible affect as global perceptions of said destination can negatively shift after such an event.


Local communities will be affected by all of the impacts outlines above. It can influence their lifestyles and way of working for many years. For example, impacts on fisheries can affect both food production for a population as well as economic positions. Populations in proximity to the spill may also experience health impacts through direct exposure to the oil, or secondary impacts such as air pollution.

How emergency services plan oil spill response

Real-world examples

Exxon Valdez

On 23rd March 1989 the Valdez oil tanker struck Bligh Reef in Prince William Sound, Alaska. More than 11 million gallons of crude oil were spilled causing devastation across thousands of miles. This spill is estimated to be one of the more expensive in history and still, 20 years later, the oil not removed continues to be a problem.

Key impacts:

  • Wildlife: It’s estimated that 250,000 seabirds, 2,800 sea otters, 300 harbour seals, 250 bald eagles and up to 22 killer whales were killed.
  • Environment: Over 1,300 miles of shoreline was affected by the oil and it’s estimated that 16,000 gallons are still present in the waters of Prince William Sound. Clean-up teams working on the Exxon Valdez spill have estimated that shoreline habitats, such as mussel beds, which have been affected will take up to 30 years to recover fully.
  • Economy: The local fishing industry experienced over $300 million in economic harm and clean-up costs reached around $2.5 billion, with total costs coming to around $7 billion.
  • Tourism: Tourism-related spending decreased by 8 percent in south-central Alaska and by 35 percent in southwest Alaska in the year after the spill.

Deepwater Horizon

  • Wildlife: Scientists have found that dolphins are still showing the effects of Deepwater Horizon 10 years afterwards. Even worse, their offspring are showing the same traits, meaning the damage could be transmittable across generations.
  • Tourism: Hotel cancellations throughout the Gulf Coast rose to 35% 2 weeks after the spill, and reached 60% after 6 weeks, with total leisure visitor spending dropping by $247 million in the year of the disaster.


The FSO SAFER is a floating oil tanker located in the Red Sea off the Yemeni coast which is at risk of spilling tonnes of oil through a leak or an explosion. Due to degradation, this situation has become a global concern and the spill has the potential to be 4x larger than the Exxon Valdez.

Download our full case study on FSO SAFER

Key potential impacts modelled by Riskaware in 2020:

  • Environment: Water and coastline contamination could extend to the Bab-el-Mandeb strait and the Gulf of Aden. In the event of a fire 40% of agricultural land may be covered in deposits from the smoke.
  • Economy: 100% of fisheries are at risk of being impacted, ports would close, and $70 million could be lost in agriculture production. Fuel prices would resultantly spike due to the closure of ports, and the fish stock could take over 25 years to recover, altogether increasing the need for humanitarian aid and food aid significantly. The overall costs of clean-up could reach $20 billion.
  • People: A fire onboard the FSO SAFER could expose over 8 million people to air pollution from the resulting smoke plumes, alongside the potential for contaminated water supplies from an oil spill. Roughly 4 million people, including fishermen and farmers, could lose their livelihoods causing mass moves inland.

How can these impacts be avoided? 

Time is of the essence in these situations. The longer the oil is in the water, the further it will spread and the more deeply the consequences fill be felt. In some incidents oil has been found for years after the initial event – continuing to cost money and degrade environments during this time.

Preventing any further spillage, as well as containing and cleaning up the oil that has been spilled, is therefore imperative for minimising these impacts. In particular, safeguarding the nearby coasts and land will often be a priority for responders as impacts to these areas can be some of the most severe.

Oil spill models, such as the one developed by Riskaware, can help reduce the environmental, economic, and humanitarian impact of a spill. These models can predict the oil’s trajectory on the surface of the water, allowing response teams to direct their activity and aim to mitigate spread in a targeted way. As an incident progresses, modelling can also show the potential for shoreline impact, helping optimise clean-up operations.

A huge benefit of this technique is that it can be employed before regular surveillance operations, for a faster and more informed response.

Learn more about the emergence of oil spill modelling for effective response

Download our MarineAware brochure or view our case studies for more information about our oil spill modelling solution.

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