A cautionary tale: deep sea exploitation and five reasons to be careful
A team of scientists from around the world have joined together to call for a strong precautionary approach in extractive activities in the deep sea, as the science needed to evaluate risks lags far behind.
Joining scientists from Oregon State University, University of California Santa Cruz, National Institute of Water and Atmospheric Research in New Zealand and University of Bergen in Norway, Helena McMonagle from the School of Aquatic and Fishery Sciences (and a guest student at Woods Hole Oceanographic Institution) worked on the study published in Communications Earth & Environment.
Recognizing the drivers behind deep sea exploitation including food and energy insecurity as a result of climate change and conflict, the team’s research highlights five reasons to proceed with caution when looking for new sources of metals for energy infrastructure, food and other critical materials.
Deep sea extraction involves the ocean’s mesopelagic zone, which lies at a depth of ~200 and 1,000m. This ocean zone is teeming with life and is a vital part of the global ecosystem, contrary to original assumptions that it was a lifeless zone. Scientific understanding of the mesopelagic zone and the impact of extractive activities trails behind the industry exploration and is the basis of the joint call by scientists to take a precautionary approach.
Why is the mesopelagic zone so important? Home to roughly 2-16 billion metric tons of fish biomass, the mesopelagic is one of the largest habitats on Earth. This rich biodiversity spans fish, crustaceans, squid, jellyfish and many other organisms.
The location of the mesopelagic zone also means it’s crucial for climate regulation. The oceans absorb about a quarter of carbon dioxide emissions, and for it to be stored for long time periods it must pass through the mesopelagic zone to the deep sea. In addition to chemical processes that allow the oceans to absorb our emissions, the biological processes play an important role too. One of these biological processes that can move carbon deep is the daily vertical migrations of mesopelagic animals. The biodiversity in the mesopelagic zone also supports important fisheries species.
Switching gears to focus on the mesopelagic zone as a source for human food may not be economically feasible or a particularly sustainable option. The densities of these fish in the ocean are relatively low and would require extraction on a large scale with low, fuel-inefficient catch rates. These fish are generally not suitable for direct human consumption, so they would need to be highly processed to make fishmeal or nutritional supplements. This can increase the waste and decreases the efficiency of this potential food source..
Deep seabed mining presents issues around large sediment plumes being left behind in an environment that hosts species that are not adapted to interact with seafloor sediments, with a single mining site able to discharge 1 Empire State Building worth of mineral dust every three weeks. Cost-benefitting analyses are also in their infancy, with less than 2% of scientific categories for environmental impact assessments having sufficient knowledge for evidence-based decision making.
As we progress through the UN Decade of Ocean Science for Sustainable Development, the team of scientists remind us that it remains vital to ensure future food and energy security solutions align with environmental sustainability.
