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Humans responsible for deep sea scars

Posted on behalf of Yana Balling

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Scientists have for the first time assessed the extent to which various kinds of human activity are damaging the seabed in the most intensely affected region of the Atlantic Ocean. Writing in the journal Plos ONE, they report that bottom trawling related to commercial fisheries leaves a greater physical footprint on the seafloor than the combined effects of all other human activities, including scientific research, fossil fuel recovery and waste disposal.

Covering approximately 60 percent of our planet’s surface, the deep sea is a major component of the Earth’s biosphere. It hasn’t yet been as excessively exploited, and hence disturbed, as the shelf regions of the world’s oceans – but this may change in the future as resources from shallow marine environments are getting rapidly depleted while deep-sea technology advances.

The study, led by Angela Benn of the UK’s National Oceanography Centre, is a first attempt at determining the physical footprint of human activities on the deep seabed. Previous investigations of human impacts on the seafloor have been restricted to comparably accessible waters shallower than 200 meters.

The team chose as study site an area comprising 11 million square kilometers – the so-called OSPAR maritime area – in the North East Atlantic, one of the most heavily impacted regions of the deep sea. Disturbances to the seabed there stem from bottom trawling, oil and gas installations, submarine communication cables, marine scientific research and from the – now banned – dumping of radioactive waste, munitions and chemical weapons.

The scientists found that about 28,000 km2 of the investigated seabed area were affected by human activity, including past activity, in 2005. Disturbances caused by non-fisheries scientific research, communication cables and waste disposal are rather small, the study finds. Disturbances caused by the oil and gas industry and by fisheries-related scientific research are classified as moderate. The spatial extent of the overall study area affected by bottom trawling was at least ten times larger than the area prone to disturbances caused by all other activities scrutinized. The impact of bottom trawling may be even more severe as much of the area is being trawled several times per year.

The scientists assessed the extent of damage by means of data provided by various companies and institutions for the year 2005. They focused on direct physical disturbances, ignoring any additional ecological and environmental impacts such as caused by the leakage of chemical substances or radioactive material.

Data availability proved an issue, though.

“Some governments, public organisations and private companies were far more forthcoming with information than others,” says Benn. “Significant improvements are needed in data collection and availability.”

Image: Damaged cold-water coral reef off Troms county, Norway. Image courtesy: MAREANO, Institute of Marine Research, Norway.

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