Scientists urge caution, further assessment of ecological impacts above deep sea mining

Currently 30 exploration licenses cover about 580,000 square miles of the seafloor on the high seas and some countries are exploring exploitation in their own water as well. Most research assessing the impacts of mining and environmental baseline survey work has focused on the seafloor.

However, large amounts of mud and dissolved chemicals are released during mining and large equipment produces extraordinary noise -- all of which travel high and wide. Unfortunately, there has been almost no study of the potential effects of mining beyond the habitat immediately adjacent to extraction activities.

"This is a call to all stakeholders and managers," said Jeffrey Drazen, lead author of the article and professor of oceanography at UH Manoa. "Mining is poised to move forward yet we lack scientific evidence to understand and manage the impacts on deep pelagic ecosystems, which constitute most of the biosphere. More research is needed very quickly."

The deep midwaters of the world's ocean represent more than 90% of the biosphere, contain 100 times more fish than the annual global catch, connect surface and seafloor ecosystems, and play key roles in climate regulation and nutrient cycles. These ecosystem services, as well as untold biodiversity, could be negatively affected by mining.

This recent paper, published in the Proceedings of the National Academy of Science, provides a first look at potential threats to this system.

"The current study shows that mining and its environmental impacts may not be confined to the seafloor thousands of feet below the surface but could threaten the waters above the seafloor, too," said Drazen. "Harm to midwater ecosystems could affect fisheries, release metals into food webs that could then enter our seafood supply, alter carbon sequestration to the deep ocean, and reduce biodiversity which is key to the healthy function of our surrounding oceans."

In accordance with UN Convention on the Law of the Sea (UNCLOS), the International Seabed Authority (ISA) is required to ensure the effective protection of the marine environment, including deep midwater ecosystems, from harmful effects arising from mining-related activities. In order to minimize environmental harm, mining impacts on the midwater column must be considered in research plans and development of regulations before mining begins.

"We are urging researchers and governing bodies to expand midwater research efforts, and adopt precautionary management measures now in order to avoid harm to deep midwater ecosystems from seabed mining," said Drazen.