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Overfishing and climate change are the culprits, and a top UCPH ecologist explains why to the University Post
Human behaviour has been identified as the main driver of a dramatic loss in ocean biomass. This is according to a new report by the WWF. Marine mammals, birds, reptiles, and fish populations have suffered a 49 per cent reduction between 1970-2012. Commercial fish stocks have been hit hard, with a 74 per cent decline in the family that includes tuna and mackerel.
Over-exploitation of ocean resources has often been depicted as a classic ‘tragedy of the commons’, or a ‘race to catch fish’ according to the WWF. Modern technological advances in fishing techniques have increased catch and profits, but in many cases we are removing species at a faster rate than they can reproduce. The maths are simple under a business-as-usual scenario: the future looks bleak not only for certain species, but also for future human populations whose food sources will have been compromised by our generation.
Katherine Richardson: “Decreasing the biomass of large organisms in the ocean has huge knock-on effects for the planet as a whole”.
“We forget that nature in the ocean operates according to different ‘ground rules’ than nature on land,” according to Professor Katherine Richardson from the University of Copenhagen’s (UCPH) Centre for Macroecology, Evolution and Climate.
“The most important process structuring ecosystems in the ocean is predation – and what is fishing? Predation! Therefore, fishing has huge impacts on marine ecosystems and marine biodiversity,” says Katherine Richardson.
The top predators of the oceans – mankind – use mobile phones, GPS systems and the best technology that marine engineering can offer in order to maximise catch while minimising effort. Climate change also bring negative effects to the ocean. Increasing atmospheric carbon dioxide is absorbed in the ocean, raising its acidity level, which in turn reduces the capacity for calcifying organisms to produce ‘skeletal’ structures. These organisms form a vital part of the oceanic food web, while the white cliffs of Dover in the UK, and Møns Klint in Denmark provide spectacular reminders of their role in the Earth’s history.
“Life started in the oceans and the oceans cover 2/3 of the planet, and life in the ocean is incredibly important for regulating processes that control the state of the entire Earth System. For example, carbon cycling. Decreasing the biomass of large organisms in the ocean has huge knock-on effects for the planet as a whole,” explains Richardson.
Coral reefs are vulnerable to climate change-induced ocean acidification and temperature rises, and are home to 25 per cent of all marine species. According to the WWF they also support around 850 million people through economic, social and cultural services. They may also be extinct within 50 years according to the research.
Katherine Richardson: “We can identify a ‘safe operating space’ for human perturbation, i.e. a level of perturbation that does not dramatically alter the function of the system as a whole.”
Is it all bad news?
Not necessarily, according to Katherine Richardson: “For our own sakes, i.e. not the sake of the ocean or the planet, we need to begin to manage not just fisheries but the interaction between fisheries and the ocean ecosystem function. Obviously, we cannot stop human perturbation of the oceans (or the planet as a whole) but we can identify a ‘safe operating space’ for human perturbation, i.e. a level of perturbation that does not dramatically alter the function of the system as a whole. We need to focus research on identifying this safe operating space and to manage our interactions with the ocean so that the boundaries of this space are respected.”
The evidence of significant ocean biomass loss should serve as a wake up call to a thoughtful society.
“There is no reason to believe that marine biodiversity is less worthy of or less in need of protection than biodiversity on land and, yet, we seldom think or worry about it,” says Richardson.
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