Marine Oil Spills Environment Impact

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13th National Plan Environment and Scientific Coordinators Workshop 2004

The Environmental Impact Of Marine Oil Spills
Effects, Recovery and Compensation
Dr. Brian Dicks
Technical Team Manager, International Tanker Owners Pollution Federation Ltd Paper presented at the International Seminar on Tanker Safety, Pollution Prevention, Spill Response and Compensation, 6th November 1998, Rio de Janeiro, Brazil

INTRODUCTION The short-term effects of oil spills on marine species and communities are well known and predictable. However, concerns are often raised about possible longer-term ("sub-lethal") population effects through, for example, low levels of residual oil affecting the ability of certain species to breed successfully. In fact, extensive research and detailed post-spill studies have shown that many components of the marine environment are highly resilient to short-term adverse changes in the environment in which they live and that, as a consequence, a major oil spill will rarely cause permanent effects. The marine ecosystem is a highly complex environment and natural fluctuations in species abundance and distribution are a feature of the normal way it functions. These fluctuations can be large and difficult to relate to particular causes, as well as difficult to measure adequately. Against this background it is inevitably difficult to establish the precise extent and likely duration of environmental damage caused by an oil spill and to distinguish such impacts from changes brought about by a variety of other factors, both natural (e.g. climatic or hydrographic changes) and man-made (e.g. commercial fishing or other industrial pollution). Despite the scientific evidence that is available to the contrary, there is frequently a basic presumption that damage must have been caused by an oil spill, and terms such as "injury", "harm", "loss" and "impairment" are used without reference to any defined meaning or reliable evidence of a causal link. There is also a presumption that everything has a price and that money can always compensate for the damage. In truth, the natural recovery of an affected area is frequently rapid and man is rarely able to do more than help speed up the process through judicious clean-up and restoration. It follows, therefore, that there is a limit to the extent that compensation obtained from the 'polluter' can be used to the direct benefit of a damaged environment. This paper briefly summarises the impact of oil spills on different components of the marine environment, as well as the potential for natural recovery and man-made restoration/re-instatement measures, as envisaged under the international compensation Conventions. BIOLOGICAL IMPACTS AND THE RECOVERY PROCESS

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13th National Plan Environment and Scientific Coordinators Workshop 2004

Impacts The environmental impact of oil spills has been extensively researched over the past 30 years and a considerable amount has been learnt about the nature and duration of such effects. As a result, our predictive capability is probably better for oil spills than for many other types of marine pollutant. The range of biological impacts after an oil spill can encompass: • • • • Physical and chemical alteration of natural habitats, e.g. resulting from oil incorporation into sediments; Physical smothering effects on flora and fauna; Lethal or sub-lethal toxic effects on flora and fauna; Changes in biological communities resulting from oil effects on key organisms, e.g. increased abundance of intertidal algae following death of limpets which normally graze the algae.

More detailed consideration is given to impacts on a range of habitats and species later in this paper. Recovery The seriousness of oil spill impacts is primarily related to the speed of recovery of the damaged habitats and species. However, misunderstandings often arise because of the use of different criteria to determine recovery. Given the difficulties of knowing...
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