Cross-sectoral management

The old man and the sea: a necessary change of course

Can man exhaust the oceans? Boris Worm, a specialist in marine biology at Dalhousie University in Halifax (Canada), believes that the stocks of species currently fished could collapse by the middle of the century. (1) But he is not a man to panic and is pursuing research on how to reconcile man and the marine environment by seeking new ocean management models. He suggests moving from a local and segmented approach to a more global ecosystem-based one as a way of preserving the essential biodiversity and survival of the oceans… and of man.

Boris Worm "There is strong evidence of pollution  along our coasts and we are seeing more and more ‘dead zones’” Boris Worm "There is strong evidence of pollution along our coasts and we are seeing more and more ‘dead zones’”
“To date, fishing has  been managed per species. The  ecosystemic approach seeks to embrace an ecosystem in its globality.”. © Shutterstock “To date, fishing has been managed per species. The ecosystemic approach seeks to embrace an ecosystem in its globality.”. © Shutterstock

The ocean cannot absorb man’s impact indefinitely. What are the visible signs of this?

They are many and varied. Fish populations are thinning and global catches slowly declining, despite increased fishing and more effective methods. Many experts agree that the exploitation limit has been reached if not exceeded. At the same time, there is striking evidence of pollution along our coasts. We are seeing more and more of these famous “dead zones” where mass planktonic algae blooms appear. When they decompose on the seabed they deplete the oxygen in the water, suffocating all the marine animals in the zone. Global warming is also reducing the planktonic communities at the base of the food chain and affecting the fish populations that feed on them, thereby throwing the complete coastal ecosystem out of balance.

The World Bank estimates that 50% of the world’s population lives less than 60 km from the sea and the figure is rising all the time…

Yes, this is a real challenge for humanity. Coastal ecosystems are very important for ocean life. They filter and transform a great deal of waste and pollutants that we discharge into the sea. For example, a single oyster colony will filter the waters of an entire bay in just a few days. They are also reproduction sites, nurseries and feeding areas for so many marine species: fish, mammals and birds. The pollution and destruction of zones such as mangroves or underwater seagrass beds leads to a deterioration in water quality and an increase in health risks linked to the consumption of sea products. The planktonic blooms I just mentioned kill the fish and contaminate the molluscs, making them dangerous for consumption. Although these are natural phenomena, the input of nutrients – mainly due to nitrogen fertilizers used in agriculture entering the sea – makes them worse. The frequent appearance of these blooms probably indicates that important ecological processes are being impaired or thrown out of balance.

Your recent studies lead you to envisage a collapse in the majority of fish stocks by the middle of the century.(1) Is the fishing industry really as badly managed as that?

Few fisheries are well managed. The overcapacity of fleets, excessive quotas compared to scientists’ recommendations, and illegal fishing practices are the main causes of resource depletion. For example, in the case of the North Sea cod the International Council for the Exploitation of the Sea (ICES) estimates that declared catches are no more than between 35% and 65% of what is actually caught and points to deficient management in verifying catches. These problems are further exacerbated in regions fished by several countries, such as the open sea or the Mediterranean where there is a lack of regulations or checks, and conflicts of interest are common.

Some people think that it is enough to wait for a depleted stock to recover. Is it that simple?

Certainly not. We are already seeing that many depleted fish stocks fail to recover after a prolonged decline. The Newfoundland cod has not been fished for over 15 years, for example, but its stock remains unreplenished. It takes years or even decades for a stock to recover as often it is the entire ecosystem that has suffered. For example, when a population of predators is decimated, small species proliferate, feeding on the eggs and larvae of the predators that are consequently unable to recover. In eastern Canada, herring stocks increased following the decline in the cod that feed off them. You may think that the cod would therefore have more food and that the cod stocks would then recover more quickly. But that overlooks the fact that herring feed on cod larvae, thereby preventing stock replenishment. Other species probably also need to be taken into account when studying this kind of interaction – one that involves the entire ecosystem – when developing and implementing management measures. Biodiversity is of critical importance, both between species and within the same species, as genetic diversity is a richness that provides opportunities for a destabilised species to adapt.

And what would such an ecosystem-based system consist of?

To date, fishing has been managed per species. The ecosystemic approach seeks to embrace an ecosystem in its globality, as a unit, and to study its component parts and their interdependencies in arriving at an appropriate method of management. It takes into account not only interactions between species, climate and oceanographic changes, variations in water quality and habitat, but also the full range of human activities influencing the marine environment, such as fishing, tourism, oil drilling, coastal planning and polluting activities. By integrating all these different dimensions we seek to put into place a management system that is able to adapt to change. The aim is to provide an optimal response to all of society’s expectations. Admittedly, further research is needed to better understand marine systems, but our knowledge is already sufficient to implement these approaches. We must start now and progressively complete our knowledge by studying the effects of the measurements we take. Waiting until we acquire an in-depth expert knowledge of marine ecosystems before envisaging this management model is most certainly not the right solution.

Many people speak of extending and increasing the Marine Protected Areas

The MPAs(2) are the cornerstone of ecosystem management. They provide a refuge for many species, preserve fragile habitats and make it possible to limit the impact of management errors made in other places. They are also useful reference zones for assessing the condition of ecosystems. The MPAs cover 1% of the world’s oceans, while many scientists believe that between 20 % and 30 % of oceans should be protected.(3) One interesting idea is to organise the MPAs into networks, each area being separated from another by a sufficient distance to permit exchanges between species and spawn. This would increase their ability to resist disruptions. The cost of maintaining such a global network is estimated at between 5 and 19 billion dollars a year. The operation would create about a million jobs. This is less than the cost of current aid to the fishing industry (between 15 and 20 billion dollars a year). So why not envisage a reallocation of this aid?

Finally, what would you like to say to those responsible for managing our oceans?

As a scientist, I would recommend that ecosystemic management should be widely introduced to restore depleted species, protect important habitats, control pollution and protect threatened species. Aid that encourages fishing overcapacity should be redirected to support better management of fisheries and the preservation of ecosystems. Legislation to introduce economic incentives would be another way of encouraging the fishing community to adopt practices that show greater respect for the marine environment. Such approaches have already had positive effects, both for marine ecosystems and for those who make their living from the sea.

François Rebufat

  1. Science, 3 November 2006, vol. 314
  2. See article, Untangling the fishing nets
  3. Figures drawn up at the 5th World Parks Congress, Durban in 2003


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