Craig R.Smith, Verena Tunnicliffe, Ana Colaço, Jeffrey C.Drazen, Sabine Gollner, Lisa A.Levin, Nelia C.Mestre, Anna Metaxas, Tina N.Molodtsova, Telmo Morato, Andrew K.Sweetman, Travis Washburn, Diva J.Amon
We thank Dr Verlaan  for offering a legal opinion on the United Nations Convention for the Law of the Sea (UNCLOS) and its protections for the marine environment, inspired by reading our paper . We agree that scientists and lawyers should work together to formulate deep-sea mining regulations; to this end, we have jointly authored 19 publications with lawyers on topics related to human impacts in the deep sea. We also agree that regulatory decisions concerning seabed mining must be informed both by accurate interpretations of the law and by accurate application of the best available scientific evidence.
We disagree that our paper  is a ‘well-intentioned but inaccurate legal analysis’ , because it is not a legal analysis. It is a scientific paper highlighting misconceptions about the potential environmental impacts of seabed mining that result when the best available scientific evidence is overlooked.
We feel obligated to point out four areas of scientific inaccuracy and misrepresentation in the critique of our paper . First, Verlaan  speculates that we are suggesting ‘that a ‘miniscule [sic] effect’ argument can legally be made to ignore or permit harmful effects.’ Rather than a legal argument, we are warning against misrepresenting threats from seabed mining to deep-sea ecosystems by comparing the spatial scales of mining disturbance with the area of entire ocean basins  (https://ran-s3.s3.amazonaws.com/isa.org.jm/s3fs-public/documents/EN/SG-Stats/dsm-hamburg.pdf). Such arguments appear to be based on the misconception that the deep seafloor is largely a single, homogeneous habitat. Numerous peer-reviewed papers provide scientific evidence that deep seafloor habitats and their characteristic biotas can be heterogeneous on scales ≥10 kilometers (e.g., [2,4,5]). Thus, seabed mining disturbance occurring over scales much smaller than ocean basins may threaten unique habitats and biodiversity [6,7]. We note that mining for polymetallic nodules at the scales currently under consideration in the Clarion-Clipperton Zone (CCZ) could alter habitat structure and biodiversity over >500 000 km2 of seafloor (i.e., an area roughly the size of France) and threaten substantial proportions of unique nodule habitat .
Second, Verlaan  questions our statement that areas targeted for seabed mining include ‘wilderness.’ Hydrothermal vents, many seamounts, and abyssal areas beyond Exclusive Economic Zones (EEZs) remain among the most intact ecosystems on the planet [8,9] and fit the definition of ‘wilderness’ in scientific usage (i.e., ‘areas devoid of intense human impacts’) .
Third, the statement, “‘Conservation” is required for natural resources, not ecosystems…’ , is at odds with the science of conservation biology, in which a major conservation objective is the protection of entire ecosystems . Conservation biology has led to the principles of ‘ecosystem-based management’ that underpin the ISA’s Regional Environmental Management Plan for the CCZ, which aims to ‘Maintain regional biodiversity, ecosystem structure and ecosystem function…’ (ISBA/17/LTC/7, https://isa.org.jm/files/files/documents/isba-17ltc-7_0.pdf). Thus, conservation of marine ecosystems is a fundamental component of scientifically based marine spatial planning and environmental management .
Fourth, it is also scientifically inaccurate to suggest that ‘the less “pristine” the marine environment, the greater the risk of harmful effects from activities; hence the more its protection is required.’ Current views in conservation biology call for prioritizing protection of wilderness areas because they often contain ‘high genetic diversity, unique functional traits, and endemic species; maintain high levels of ecological and evolutionary connectivity; and may be well placed to resist and recover from the impacts of climate change’ . The need to protect ‘naturalness’ has been recognized in the United Nations Convention on Biological Diversity Conference of the Parties Decision IX/20 Annex I with the goal ‘to protect areas with near natural structure, processes and functions,’ ‘to maintain these areas as reference sites,’ and ‘to safeguard and enhance ecosystem resilience’ (https://www.cbd.int/decision/cop/?id=11663).
In closing, we agree that environmentally responsible regulation of human activities in the ocean requires both sound legal analyses and scientific evidence . However, the design of scientific research and the collection and interpretation of scientific data are the responsibility of scientists, who must ensure that the best scientific evidence is available and used. A clear understanding of the environmental consequences of seabed mining based on scientific evidence is key to most efficiently managing human activities in the ocean to maintain biodiversity, ecosystem structure, and ecosystem services.
Finally, we applaud Verlaan  for stressing the uncertainties regarding the multiple adverse impacts of human activities on the ocean: ‘The marine environment is acidifying, warming, deoxygenating, becoming noisier, brighter, overfished, and more polluted. It is legally and scientifically unclear how to disentangle and regulate these and other adverse effects of human activities from those specifically related to sea-bed mining’ . This argument highlights the need for a precautionary approach in proceeding with deep seabed mining due to our poor understanding of deep-sea ecosystems and mining impacts and the potential for interactions with other anthropogenic threats to the marine environment .