The work, in which ICM-CSIC researcher Erik Simon-Lledó has participated, also reveals the first signs of biological recovery in an area of the Pacific that was intensely exploited 44 years ago.
New study led by the UK’s National Oceanography Centre (NOC) and the Natural History Museum has revealed long-term impacts of deep-sea mining and first signs of biological recovery 44-years after deep-sea trails in the Pacific Ocean. The work, in which the ICM-CSIC researcher Erik Simon Lledó has participated, has been published recently in Nature and provide critical evidence to the global deep-sea mining debate.
To carry out the study, the scientific team visited a previously mined site in the Clarion Clipperton Zone (CCZ). This allowed them investigate if recovery is possible and what impact remains 44 years after the machines have left. Results show that mining has clearly caused long-term changes to the sediments but the effects on the animals living at these depths is more variable.
Lead author and expedition leader, Daniel Jones of the National Oceanography Centre explains:
“To tackle the crucial question of recovery from deep-sea mining, we need first to look to the past and use old mining tests to help understand long-term impacts. Forty-four years later, the mining tracks themselves look very similar to when they were first made, with an 8-metre-wide strip of seabed cleared of nodules and two large furrows in the seafloor where the machine passed“.
In these directly impacted tracks, 44 years later, the abundance and diversity of fauna remained substantially lower than in adjacent, non-mined areas. “While some mobile species appeared to have returned to the mined tracks, showing signs of an initial recovery, the megafaunal community was still missing an important ecosystem component, the sessile fauna” adds Erik Simon-Lledó, from the ICM-CSIC. He concludes
“The hard substratum provided by nodules is essential for the growth of many species in abyssal Pacific seascapes. As occurs in a degraded forest, squirrels can only return when the trees they inhabit grow back, yet the polymetallic nodules where many corals, anemones or sponges grow will take millennia to develop again”.
In this regard, Jones points out that “the evidence provided by this study is critical for understanding potential long-term impacts. Although we saw some areas with little or no recovery, some animal groups were showing the first signs of recolonisation and repopulation”.
Deep-sea mining is increasingly being considered as a potential solution to the growing global demand of crucial metals like nickel, copper, or manganese, along with rare earth minerals. A key area of interest for mining is the CCZ, a vast region in international waters of the Central Pacific Ocean that it is home to unique and biodiverse deep-sea creatures, many yet to be described by science, as well as a rich mineral resource of polymetallic nodules, highly enriched in metals. At depths of nearly 5,000m on the seabed of the CCZ, the abundant potato-sized rocks represent one of the most abundant deep-sea mineral resources.
The International Seabed Authority (ISA), established in 1994 under international law, is deciding whether to allow deep-sea mining in the region and under what conditions. A key question in this decision, is whether deep-sea ecosystems can recover from mining disturbances.
In the 1970s the first of industrial trials of deep-sea mining were carried out in the Pacific. It was this site that Prof. Jones and his team visited in 2023, onboard the world-class Royal Research Ship James Cook, equipped with the cutting-edge underwater robot submersible Isis, to explore and study the aged mining tracks deep beneath the ocean's surface.
The study forms part of the NOC-led Seabed Mining and Resilience To EXperimental Impact (SMARTEX) project – funded by the Natural Environment Research Council (NERC). All the data collected is made available to all stakeholders to guide future policy decisions by the ISA and the nation states involved.