Mining the deep seabed will harm biodiversity. We need to talk about it

In 2017, Japan became the first country to test mining ocean minerals on a significant scale. While its operation took place at depths of about 1,600 metres, many deep seabed minerals are much deeper - more than four kilometres down. These are pitch-black environments in which pressures are bone-crushingly high, and life operates on a completely different timescale. At these depths, mistakes can be costly for both industry operators and the environment.

Mining the deep seabed for minerals such as copper, nickel, tin, zinc, cobalt and gold is a fledgling industry. Some suggest that it could become part of the ocean economy, which is projected to double its worth by 2030, to more than $3 trillion. However, the potential success of deep seabed mining is far from certain. Several commentators are concerned about its possible environmental impacts. Furthermore, there are significant regulatory, technical, economic, and scientific hurdles yet to be cleared.

World Oceans Day recognizes the importance of our marine environments to society. It is a timely reminder that closely watching the development of new ocean industries, such as deep seabed mining, is a shared concern and responsibility.

Balancing mining with the protection of oceans that are beyond national boundaries is the task of the International Seabed Authority (ISA), an intergovernmental organization headquartered in Jamaica. The ISA is currently developing the world’s first international regulations for commercial-scale seabed mining. The ISA will need to set environmental management goals and objectives. However, an open and honest conversation about what environmental standards are achievable for seabed mining is yet to be had.

Together with our co-authors, we argue in this study that biodiversity loss is unavoidable for the industry. The ecological consequences of a loss of biodiversity in the deep sea are poorly understood. For example, we do not yet understand the role that the deep sea plays in delivering essential global ecosystem services, such as climate regulation through the storage of carbon.

These largely unknown systems are a living library, much like our tropical rainforests, from which the next medical breakthroughs may be discovered. Losses of this kind could have wide-ranging and significant implications. As such, it is widely accepted that the industry should be developed in a precautionary and responsible manner.

A commonly used goal for responsible mining on land is to achieve 'no net loss' of biodiversity. Financial and regulatory frameworks increasingly require extractive industries to apply a four-tier mitigation hierarchy to manage impacts to biodiversity, whereby losses should be:

1) avoided and

2) minimised to the greatest extent possible before

3) remediation and

4) offsetting opportunities are explored.

But each step of this mitigation hierarchy will be very difficult to apply to deep seabed mining. Avoidance and minimization of biodiversity loss from mining (steps one and two) should be prioritized and optimized through technical innovation of the industry. Nonetheless, the extractive nature of the activity, which inevitably destroys species and habitats, means that biodiversity loss will occur at this first stage.

The third step, remediation, seeks to alleviate these residual losses at and around a mine site, and is critical to its long-term sustainability. At present, it is questionable whether remediation is feasible in the deep sea, given that many of the species have long lives and grow extremely slowly, making them unlikely to recolonize disturbed habitat in human time frames. The challenge is further increased by the enormous spatial scale of mines for some types of minerals, and the high financial costs of working in these remote and harsh environments.

Biodiversity offsetting is the last resort, and most controversial stage of the mitigation hierarchy. It has been proposed as a way to address the unavoidable residual impacts of industry. In theory, biodiversity offsets provide equivalent gains in biodiversity to that lost through an activity. Creating additional deep sea biodiversity is currently problematic for a variety of reasons, not least of which is the scientific understanding needed for deep sea restoration. This knowledge and experience is not yet available, and acquiring it will be slow and costly.

Another management option could be to protect an area from existing harmful activities, such as deep sea bottom fishing, to allow for natural recovery of that area instead. But proposed mining and ongoing fishing generally target completely different ecosystems at different locations and depths. Additionally, the administration of such a 'swap' would be severely hampered, because there is no overarching governance institution that manages both mining and fishing on the high seas. Unlike mining, anyone can fish on the high seas, meaning that areas closed to fishing need broad international agreement in order to be meaningful. Otherwise, other states will simply step into areas that others have vacated.

A further challenge is the need to demonstrate the 'additionality' of an offset, meaning that it must be a conservation activity that would not have happened otherwise. For example, biodiversity loss from a deep-sea mine cannot be offset through an existing or already planned marine park. Protection of an area as an additional source of biodiversity benefit would need to demonstrate that the area protected as an offset is at risk of future degradation. This can be extremely challenging to prove, particularly in international waters. Without this assurance, purported offsetting can actually perpetuate losses of biodiversity.

Meaningful offsets would need to protect ecosystems similar to the ones harmed by mining. 'Like for like' offsetting is difficult in the deep sea, because many species there occur nowhere else. Consequently, 'out of kind' offsetting mechanisms have been proposed. These include creating dissimilar biodiversity benefits and may promote ecosystem functions and services that fundamentally differ from those that were lost. These benefits may accrue to different stakeholders and different ecosystems.

One example would be to increase the fisheries productivity in shallow water to replace deep-sea biodiversity losses. While perhaps beneficial where they occur, these 'out of kind' activities are not true offsets, in the sense of helping the deep-sea ecosystems under threat. They actually risk masking irreversible biodiversity loss.

In our view, biodiversity offsets are not a feasible option to manage the environmental harm of deep seabed mining. No net loss of biodiversity is currently considered impossible for this industry. Accordingly, to minimize the risks posed by biodiversity losses through deep seabed mining, regulators will need to focus on the first two steps of the mitigation hierarchy: avoidance and minimization measures, including setting aside mineable areas and developing, testing and applying mining technology that minimizes impact.

The international seabed and its mineral deposits are legally classified as the 'common heritage of mankind'. Accordingly, the ISA is managing them on behalf of us all. Seabed minerals and their associated ecosystems form over hundreds and thousands of years. Lost deep sea biodiversity is unlikely to recover within human timescales. The actions of our generation will affect the common natural heritage of every generation to come.

In view of the above challenges, we suggest that a broad and inclusive debate is needed about how to balance the proposed economic and technological benefits of mining the deep seabed with the environmental risks it would entail. What level of environmental harm is acceptable? How will the economic benefits of seabed mining be shared with future generations? Is this a real opportunity to 'do things right', or will the deep sea simply be the last in a long list of exploited frontiers?