Ocean sustainability, a challenge to be won

Editorial by Cosimo Solidoro

Oceans are a fundamental component of our planet and their contributions to human wellbeing is so large that cannot be overestimated. To provide few notables examples, they provide half of the oxygen we breath, mitigate current climate, buffer climate change impact and slow down its rate by adsorbing massive amount of heat and of CO2 from the atmosphere, offer foods, recreation, spiritual experiences, and inspiration for culture to many communities.

They also represent a formidable asset to sustain economic growth and fight poverty into the next centuries. Oceans probably host precious compounds of pharmaceutical interest still to be discovered, as well as raw material and energy useful to industry, and likely are the largest still under-exploited reservoirs of renewable resources in the planet. Indeed the concepts of Blue Economy and Blue Growth are increasingly mentioned in the political agenda and oceans exploitation already is a permanent presence in the economic arena.

At the same time, oceans are complex systems, still largely unexplored and only partially understood, in which a variety of processes interact at multiple scales, and concur in driving and constraining marine life, ocean health and related ecosystem services. In spite of the poor knowledge that our actions might have on such an important and interconnected system, marine ecosystem are exposed to the cumulative (direct and indirect, synergic antagonistic) impact of a number of co-occurring multiple stressors, resulting from multiple drivers, also acting in different area. In fact, in the oceans everything is connected, and any given source of environmental alteration (stressors) has a direct effect on specific areas and ocean component, but it can have also many indirect or cascading effects on different area and components. This also implies the existence of interdependencies among activities that somehow depend upon or impacts on marine ecosystem state.

A non exhaustive list of co-existing pressures includes climate change (and therefore warming, acidification, changes in sea level rise, changes in ocean circulation, ventilation and mixing processes, and more), pollutions (from persistent organic pollutants, i.e. substances that resist degradation and can be transported over long distances and accumulate in the environment, such as pesticides, industrial chemicals and dioxins, but also emerging pollutants, such as drugs or hormones), litter (including plastic) , maritime traffics, exploitation of living resources (fishing and aquaculture) , exploitation of non living resources (deep sea mining, extraction industry, energy), eutrophication and cultural oligotrophication, invasive species. But other menaces exist.

Some of those pressures are well known. Others are getting attention now. All are relevant. It would be naïve, and surely controversial, to ask to reduce all those pressures to zero, but we might ask to ban some of the most damaging activities, and pose reasonable constrains to other. Aquaculture represents a point in case.

Given that human population keeps on growing, aquaculture is expected to grow very substantially, up to provide an important contribution to meet world food demand. However, we might consider to chose those aquaculture practises that impact the least, i.e. to focus on low trophic level species (at land we grow herbivores but at sea we are focusing on carnivores, and we do not know how to feed them), favour integrated multi-trophic aquaculture (systems in which a cultured specie feeds on the waste of other aqua-cultured species), promote circular economy, reduce transport impacts by encouraging the consumption of local products, and so on. In other cases, in which our present knowledge on potential impacts of an activity really is too limited, or there is no consensus (consider for instance deep sea mining), we might use the precautionary principle.

Technological development gave humans the capability to modify Earth to an extent never seen before and almost detached us from the rest of the planet. But we still are animals bounded by natural laws and living

in a finite planet in which everything is connected with everything, and every action we take might have relevant, and potentially irreversible consequences on everything else. Technological success might have given us the illusions we have no limits and we can fix everything. But it is not so.

UN declared the decade 2021-2030 as the ‘UN decade of ocean science for sustainable development’. This choice highlights the importance and the potentials of the oceans, the need for science, and therefore to increase our understanding of the ocean, but also, and possible more than everything else, it calls our attention to the need of maintaining the economic development fuelled by the exploitation of ocean resources within the sustainability paradigm. Economic development, ecological sustainability, and social equity. We better be able to meet this challenge.

Cosimo Solidoro is the Director of the Oceanography Department of the National Institute of Oceanography and Applied Geophysics - OGS

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