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 they suggest.
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 defences 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 findings come in a new rapid response report entitled 'In Dead Water' which has for the first time mapped the multiple impacts of pollution; alien infestations; over-exploitation and climate change on the seas and oceans.
'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.
The report, the work of UNEP scientists in collaboration with universities and institutes in Europe and the United States, was launched today during UNEP's Governing Council/Global Ministerial Environment Forum taking place in Monaco.
It is the largest gathering of environment ministers since the climate convention conference in Indonesia just over two months ago where governments agreed the Bali Road Map aimed at delivering a deep and decisive climate regime for post 2012.
Achim Steiner, UN Under-Secretary General and UNEP Executive Director, said:' The theme of the Governing Council is 'Mobilizing Finance for the Climate Challenge for trillions of dollars can flow into climate-friendly energies and technologies if government's can provide the right kind of enabling market mechanisms and fiscal incentives'.
'It is sometimes important to remind ourselves why we need to accelerate these transformations towards a Green Economy. In Dead Water has uniquely mapped the impact of several damaging and persistent stresses on fisheries. It also lays on top of these the likely impacts of climate change from dramatic alternations in ocean circulation affecting perhaps a three quarter of key fishing grounds up to the emerging concern of ocean acidification,' said Mr Steiner.
'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 issued last week 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 be being choked after being fed on a diet of snake pipefish-a very bony species. Over the past five years snake pipefish numbers have boomed a meeting of the Zoological Society in London was told last week.
One reason for their sharp increase in numbers might be changes in ocean currents bringing the fish into North Sea waters, the experts suggest.
The new UNEP report has been compiled by researchers including ones at UNEP's GRID Arendal centre; UNEP's World Conservation Monitoring Centre and UNEP's Division of Early Warning and Assessment.
It draws on a wide range of new and emerging science including the latest assessment report of the Intergovernmental Panel on Climate Change-the 2,000 plus panel of scientists established by UNEP and the World Meteorological Organisation.
Other contributions have come from organizations and institutions including the University of Plymouth; the Norwegian Institute for Nature Research; the University of British Columbia; the Institute of Zoology; Princeton University; the University of Barcelona and the Sustainable Europe Research Institute.
In Dead Water 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.
Christian Nellemann, who headed up the rapid response team that compiled the report, said: 'We are already seeing evidence from a number of studies that increasing sea temperatures are causing changes in the distribution of marine life'.
Some of these changes are being found from the Continuous Plankton Recorder survey of the Northeast Atlantic.
Warmer water copepod species or crustaceans have moved northward by around 1,000km during the later half of the 20th century with the patterns continuing into the 21st century.
'Further evidence of this warming signal is seen in the appearance of a Pacific planktonic plant in the Northwest Atlantic for this first time in 800,000 years by transfer across the top of Canada due to the rapid melting of the Arctic in 1998,' said Dr. Nellemann. 'We are getting more and more alarming signals of dramatic changes in the oceans. It is like turning a big tanker around. Our ability to change course and reduce emissions in the near future will be paramount to success'.
The link between healthy and productive fishing grounds and ocean circulation or 'dense shelf water cascading' is in some ways only now emerging.
Three years ago the Hotspot Ecosystem Research on the Margins of European Seas of which UNEP is part, documented such a phenomenon in the Gulf of Lions in the north-western Mediterranean.
A quantity of water equal to two years-worth of the river discharge from all rivers flowing into the Mediterranean is, in four months, transported from the Gulf of Lions to the deep Western Mediterranean via the Cap de Creyus canyon.
It has a critical impact on the population of the heavily harvested deep sea shrimp Aristeus antennatus, the crevette rouge, by bringing food that in turn triggers a sharp increase in young shrimp resulting in plentiful catches three to five years after the 'cascading' event.
'Imagine what will happen if climate change slows down or stops these natural food transport and 'flushing' effects in waters that are often already polluted, heavily fished, damaged and stressed', said Dr. Nellemann. 'We are gambling with our food supply'.
Stefan Hain of UNEP's World Conservation Monitoring Centre, said it was critical that existing stresses were also addressed too in order to conserve fish stocks and coral reefs in a climate constrained world.
He said there was growing evidence that coral reefs recover from bleaching better in cleaner, less polluted waters.
Dr Hain cited monitoring of corals around the main Seychelles island of Mahé which were among corals world-wide that suffered from the high sea surface temperatures of the late 1990s. Here coral reefs recovery rates have varied between five to 70 per cent.
'Coral reefs recovering faster are generally those living in Marine Protected Areas and coastal waters where the levels of pollution, dredging and other kinds of human-induced disturbance are considered low,' he said.