Oil spills and wildlife

Oil spills, particularly where they come ashore, can be a shocking sight. In reality oil is probably a less pernicious pollutant than many others. Most oil fractions are naturally broken down in the environment, and its effects can be relatively short-lived in many environments. The heavier elements of oil, however, can remain for longer periods and where these have smothered mangrove roots, they have led to long-term changes in communities. In some cases oil may be incorporated into the sediments, only to be released during storms, which can also greatly lengthen the period of the problem.

Seabird being cleaned following an oil spill

One of the most damaging short-term impacts of oil pollution is on larger, long-lived species which spend time on the water surface, notably seabirds, but also marine mammals such as otters, seals and cetaceans. Most oil hydrocarbons are hydrophobic and lipophilic ? they spread out on the ocean surface and rapidly attach to other hydrocarbons, such as the surface lipids and oils which are found on the skin, fur and feathers of mammals and birds. In birds these surface layers are critical for preventing waterlogging and maintaining buoyancy. The clogging with heavy oil can prevent them flying, and, as they attempt to clean themselves they can ingest large amounts of oil, including toxic elements. In cooler climates this clogging also destroys their insulation. Most heavily oiled seabirds thus die of starvation, cold temperatures or toxic poisoning. Where efforts have been made to clean the birds considerable care has to be taken as the detergents which are used also remove the natural bouyancy of the feathers and this has to be allowed to return before the birds are released. Similar problems have been reported for marine otters. Seals, and cetaceans can avoid oil in most circumstances, however major oil-spills have their impact on these species too.

Massive mortalities are typically associated with large spills from tankers or pipelines rather than land-based sources however there is an ongoing chronic problem, more globally widespread which can be related to smaller spills from a broad range of sources.