Climate change is emerging as the latest threat to the world’s dwindling fish stocks, according to a report by the United Nations Environment Programme (UNEP).

At least three quarters of the globe’s key fishing grounds may become seriously impacted by changes in circulation as a result of the ocean’s natural pumping systems fading and falling.  These natural pumps, dotted at sites across the world including the Arctic and the Mediterranean, bring nutrients to fisheries and keep them healthy by flushing out wastes and pollution.

The impacts of rising emissions on the marine world are unlikely to end there. Higher sea surface temperatures over the coming decades threaten to bleach and kill up to 80 per cent of the globe’s coral reefs-major tourist attractions, natural sea defenses and also nurseries for fish. Meanwhile there is growing concern that carbon dioxide emissions will increase the acidity of seas and oceans. This in turn may impact calcium and shell-forming marine life including corals but also tiny ones such as planktonic organisms at the base of the food chain.

“The worst concentration of cumulative impacts of climate change with existing pressures of over-harvest, bottom trawling, invasive species infestations, coastal development and pollution appear to be concentrated in 10-15 per cent of the oceans,” says the report.

This 10-15 per cent of the oceans is far higher than had previously been supposed and is “concurrent with today’s most important fishing grounds” including the estimated 7.5 per cent deemed to be the most economically valuable fishing areas of the world, it adds.

“It is sometimes important to remind ourselves why we need to accelerate these transformations towards a Green Economy.” said Achim Steiner, UN Under-Secretary General and UNEP Executive Director.

“Climate change threatens coastal infrastructure, food and water supplies and the health of people across the world. It is clear from this report and others that it will add significantly to pressures on fish stocks. This is as much a development and economic issue as it is an environmental one. Millions of people including many in developing countries derive their livelihoods from fishing while around 2.6 billion people get their protein from seafood,” he said.

The report comes in wake of findings by a team led by the National Center for Ecological Analysis and Synthesis which estimates that over 40 per cent of the world’s oceans have been heavily impacted by humans and that only four per cent remain relatively pristine. It also comes amid concern that sea bird chicks in the North Sea may choke after being fed on a diet of snake pipefish-a very bony species. Over the past five years snake pipefish numbers have boomed.

Other Key Findings

  • Half the world’s catch is caught along Continental shelves in an area of less than 7.5 per cent of the globe’s seas and oceans.
  • An area of 10-15 per cent of the world’s seas and oceans cover most of the commercial fishing grounds.

  • 80 per cent to 100 per cent of the world’s coral reefs may suffer annual bleaching events by 2080 under global warming scenarios.
  • Those at particular risk are in the Western Pacific; the Indian Ocean; the Persian Gulf; the Middle East and in the Caribbean
  • Over 90 per cent of the world’s temperate and tropical coasts will be heavily impacted by 2050. Over 80 per cent of marine pollution comes from the land. Marine areas at particular risk of increased pollution are Southeast and East Asia.
  • Increasing concentrations of C02 in the atmosphere are likely to be mirrored by increasing acidification of the marine environment.
  • Increasing acidification may reduce the availability of calcium carbonates in sea water, including a key one known as aragonite which is used by a variety of organisms for shell-building.
  • Cold-water and deep water corals could be affected by acidification by 2050 and shell-building organisms throughout the Southern Ocean and into the sub-Arctic Pacific Ocean by 2100.
  • Climate change may slow down the ocean thermohaline circulation and thus the continental shelf “flushing and cleaning” mechanisms, known as dense shelf water cascading,over the next 100 years. These processes are crucial to water quality and nutrient cycling and deep water production in at least 75 per cent of the world’s major fishing grounds.
  • Dead zones, area of de-oxygenated water, are increasing as a result of pollution from urban and agriculture areas. There are an estimated 200 temporary or permanent ‘dead zones’ up from around 150 in 2003.
  • Up to 80 per cent of the world’s primary fish catch species are exploited beyond or close to their harvesting capacity. Advances in technology, alongside subsidies, means the world’s fishing capacity is 2.5 times bigger that that needed to sustainably harvest fisheries.
  • Bottom trawling is among the most damaging and unsustainable fishing practices at the scales often seen today
  • Alien invasive species, which can out-compete and dislodge native ones, are increasingly associated with the polluted, overharvested and damaged fishing grounds. The report shows that the concentration of ‘aliens’ matches with some precision the world’s major shipping routes.

(United Nations Environment Programme)