Crisis in global oceans as populations of marine species halve in size since 1970

Marine species around the world, including populations of fish critical to human food security, are in potentially catastrophic decline according to research published today.

WWF’s Living Blue Planet, an updated study of marine mammals, birds, reptiles and fish, shows a decline of 49 per cent in the size of marine populations between 1970 and 2012. As well as being disastrous for ecosystems, these findings spell trouble for all nations, especially people in the developing world who depend heavily on the ocean’s resources.

Many species essential to commercial and subsistence fishing – and therefore global food supply – are significantly depleted due to over fishing. Global population sizes of the Scombridae family of food fish that includes tunas, mackerels and bonitos have fallen by 74 per cent. Declining stocks of bluefin and yellowfin are of particular concern. Some species found in UK waters, including the vulnerable porbeagle shark and the critically endangered leatherback turtle, have also undergone precipitous declines.

While over-exploitation is identified as the major threat to ocean biodiversity, the study finds that climate change is causing the ocean to change more rapidly than at any other point in millions of years. Rising temperatures and increasing acidity levels caused by carbon dioxide are further weakening a system that is already severely degraded through overfishing, habitat degradation and pollution.

WWF Scotland director Lang Banks said: “Our oceans and seas are some the most amazing parts of our planet, and this report is a stark reminder as to what would be at risk if we do not begin to turn things around.

“However, there are many steps that all governments can take to restore our marine environment. Here in Scotland, Ministers have set an encouraging example by proposing management measures that could ensure proper protection of our Marine Protected Areas. Scotland’s fishermen are also adopting improved management measures, including more use of selective fishing nets and the avoidance of unwanted fish to minimise discards.

“Of course, to complete the job, more will need to be done. And, as we approach the next Holyrood elections, we need to see political parties commit to a fully-resourced marine monitoring strategy to support evidence-based decision-making and compliance that will help deliver the healthy seas that we all want.

“But, it’s not just politicians who can improve the things. As consumers, each one of us has the power to make a difference by ensuring that all the seafood we eat is responsibly sourced and Marine Stewardship Council accredited.”

The analysis tracked 5,829 populations of 1,234 species, from sea birds to sharks to leatherback turtles, making the data sets almost twice as large as past studies.

The report also shows steep worldwide declines in the cover of coral reefs, mangroves and seagrasses that support fish species and provide valuable services to people. It is very possible that we could lose coral reefs from most areas by 2050 as a result of climate change. With over 25 per cent of all marine species living in coral reefs and about 850 million people directly benefiting from their economic, social and cultural services, the loss of these reefs would be catastrophic.

Professor Ken Norris, Director of Science at ZSL said: “The ocean works hard in the background to keep us alive, generating half of the world’s oxygen and absorbing almost a third of the carbon dioxide produced from burning fossil fuels. It also feeds billions of people around the globe, some of whom rely solely on the oceans to survive. These devastating figures reveal how quickly human beings are changing the wildlife in our oceans and are a stark warning of the problems we might face as a result.”

It’s not all bad news in the UK. Recent assessments from the North Sea have shown that just over 50% of assessed stocks, including herring and haddock are being fished sustainably. Progress is being made in the designation of Marine Protected Areas, but the UK Government must do more to ensure delivery of a coherent and well-managed network of sites. Scotland has recently set a good example by proposing management measures that should ensure proper protection of sites.

Current gaps in the network in England include seagrass sites – home to two species of seahorse – and protection for mobile species such as sharks, skates and rays, which are identified as being in trouble on a global scale in this report.