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Oil and gas exploration poses severe risks to marine species. Better management is needed
As the name suggests, seismic surveys use seismic waves, like the ones generated during an earthquake, to explore the structure and features of the Earth’s subsurface. This type of exploration in the oceans is expanding at a rapid rate due to technological improvements and the increasing needs of our fossil fuel-based economy, so that it
As the name suggests, seismic surveys use seismic waves, like the ones generated during an earthquake, to explore the structure and features of the Earth’s subsurface. This type of exploration in the oceans is expanding at a rapid rate due to technological improvements and the increasing needs of our fossil fuel-based economy, so that it now reaches higher latitudes and deeper waters, all throughout the year. Of particular concern is the Arctic region, where the decline in sea ice coverage has opened a previously untapped potential for large-scale exploration and extraction of hydrocarbons.
The risks involved for marine species
Because of the loud noise they introduce in the marine environment, seismic surveys have raised concerns for their effects on marine life. A large body of scientific evidence highlights that these surveys can displace marine animals from their habitat, disrupt their behavior, mask their communication, cause stress and, at close ranges, even damage their hearing systems. Effects have been documented on marine mammals, but also on fish and invertebrates, suggesting that the entire ecosystem might ultimately be impacted. The low frequency of the noise also means that this can propagate across entire oceans, for hundreds, or even thousands, of kilometers.
How seismic surveys work
A marine seismic survey involves one or more ships that deploy the source of the seismic wave, generally an air gun or an air gun array. When fired (typically once or twice per minute), air guns release highly compressed air and generate an intense sound impulse directed downwards. As this acoustic wave travels through the water column and into the seabed, it reflects off layers of rock with different properties. Seismic ships also tow one or more receiver cables that contain several hydrophones (underwater microphones), which pick up the reflected echo from the seismic wave. The time of arrival and characteristics of the echo provide information on what the wave has encountered in the seabed, resulting in a detailed image of the underlying structure. Commercial seismic surveys generally aim to identify reservoirs of hydrocarbons, so that oil and gas companies know exactly where to drill to extract them. Seismic surveys are also used for research purposes to study the geophysical properties of the seafloor.
Noise as a pollutant: more regulation needed
A panel of experts from various universities and organizations across the globe authored a study published in Frontiers in Ecology and the Environment. They stress that, given the wide spatial and temporal scale over which seismic survey noise can propagate, current measures to assess, mitigate and monitor potential consequences are, at best, insufficient. Protocols are not standardized and have not been updated with the most recent scientific evidence on impacts and mitigation techniques, such as marine vibration, an alternative technology that could replace air guns. Moreover, they do not account for the cumulative and repeated exposure animals are subjected to over time, which can cause longer-term effects that are difficult to detect at a small scale.
The experts suggest that greater regional and international collaboration among governments, scientists, environmental organizations and industries is urgently needed to promote the successful coordination of management efforts and planning of activities at sea. The European Union and other regional bodies now recognize noise as a pollutant, but further international regulation that crosses national and regional boundaries is required, for example via a revision of the existing International Convention on the Prevention of Pollution from Ships (MARPOL). This would create standardized rules and protocols that would facilitate robust assessments of the potential impacts, the implementation of cutting-edge mitigation strategies and the collection of critical monitoring data.
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