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3rd October 2013

Oceans are in "critical state" due to multiple environmental impacts

A panel of marine experts is demanding urgent action to halt ocean degradation – based on findings that the rate, speed and impacts of change are greater, faster and more imminent than previously thought.




The latest report from the International Programme on the State of the Ocean (IPSO)/IUCN goes beyond the conclusion reached last week by the UN climate change panel the IPCC, that the ocean is absorbing much of the warming and unprecedented levels of carbon dioxide. It warns that the cumulative impact of this and other ocean stressors is far graver than previous estimates.

Today's rate of carbon release, at approximately 35 gigatons of CO2 per year, is at least 10 times faster than that which preceded the last major species extinction (the Paleocene Eocene Thermal Maximum, or PETM, ca. 55 million years ago), while geological records indicate that the current acidification is unparalleled in at least the last 300 million years. We are entering an unknown territory of marine ecosystem change, and exposing organisms to intolerable evolutionary pressure. The next mass extinction event may have already begun.

Falling oxygen levels in the ocean caused by climate change and nitrogen run-off, combined with other chemical pollution and rampant overfishing are undermining the ability of the ocean to withstand these so-called "carbon perturbations" – meaning its role as Earth's "buffer" is seriously compromised.

Professor Alex Rogers of Somerville College, Oxford, and Scientific Director of IPSO said: "The health of the ocean is spiraling downwards far more rapidly than we had thought. We are seeing greater change, happening faster, and the effects are more imminent than previously anticipated. The situation should be of the gravest concern to everyone since everyone will be affected by changes in the ability of the ocean to support life on Earth."

The findings, published in the peer-reviewed journal Marine Pollution Bulletin, are part of an ongoing assessment process overseen by IPSO, which brings together scientists from a range of marine disciplines. The body's previous 2011 report, which warned of the threat of "globally significant" extinctions of marine species, received global media attention and has been cited in hearings at the United Nations, US Senate and European Parliament as well as the UK Parliament.

Among the latest assessments of factors affecting ocean health, the following areas of greatest concern were identified:




Evidence is mounting that the oxygen inventory of the ocean is progressively declining. Predictions for ocean oxygen content suggest a decline of up to 7% by 2100. This is occurring in two ways: the broad trend of decreasing oxygen levels in tropical oceans and areas of the North Pacific in the last 50 years; and the rapid rise in coastal hypoxia (low oxygen) associated with eutrophication. The former is caused by global warming, the latter by increased nutrient runoff from agriculture and sewage.

dead fish


If current trends in CO2 continue, we can expect extremely serious consequences for ocean life, and in turn food and coastal protection. At CO2 levels of 450-500 ppm (projected for 2030-2050) erosion will exceed calcification in the coral reef building process, resulting in the extinction of many species and decline in biodiversity overall.



As made clear by the IPCC, the ocean is taking the brunt of warming in the climate system, with direct and well-documented physical and biogeochemical consequences. The impacts in the decades to 2050 are likely to include: reduced seasonal ice zones, with the disappearance of Arctic summer sea ice by the mid-2030s; rapid venting of the greenhouse gas methane from the Arctic seabed (a factor not considered by the IPCC); increasing stratification of ocean layers; and increased incidence of anoxic and hypoxic (low oxygen) events.

arctic sea ice melting


The 'deadly trio' of the above three stressors – acidification, warming and deoxygenation – is seriously affecting how productive and efficient the ocean is, as temperatures, chemistry, surface stratification, nutrient and oxygen supply are all implicated, meaning that many organisms will find themselves in unsuitable environments. These impacts will have cascading consequences for marine biology, dramatically altering food web dynamics and the expansion of pathogens.

Continued overfishing is serving to further undermine the resilience of ocean systems, and contrary to some claims – despite some improvements in developed regions – fisheries management is still failing to halt damage to ecosystems and the decline of key species. In 2012 the UN FAO concluded that 70% of world fish populations are unsustainably exploited, 30% of which have biomass collapsed to less than 10% of unfished levels. A recent global assessment of compliance with Article 7 (fishery management) of the 1995 FAO Code of Conduct for Responsible Fisheries, awarded 60% of countries a "fail" grade, and saw no country identified as being overall "good".




As a matter of urgency, the marine scientists say that governments around the world must:

• Reduce global CO2 emissions to limit temperature rise to less than 2°C, or below 450 ppm. Current targets for carbon emission reductions are insufficient in terms of ensuring coral reef survival and halting ocean acidification, especially as there is a time lag of several decades for atmospheric CO2 being dissolved in the ocean. Potential knock-on effects of climate change in the ocean – such as methane release from melting permafrost, and coral dieback – mean the consequences for human and ocean life could be even worse than presently calculated.

• Ensure effective implementation of community-and ecosystem-based management, favouring small-scale fisheries. Examples of broad-scale measures include introducing true co-management with resource adjacent communities, eliminating harmful subsidies that drive overcapacity, protection of vulnerable marine ecosystems, banning the most destructive fishing gear, and combating illegal unreported and unregulated (IUU) fishing.

• Build a global infrastructure for high seas governance that is fit-for-purpose. Most importantly, secure a new implementing agreement for the conservation and sustainable use of biodiversity in areas beyond national jurisdiction under the auspices of UNCLOS.

IUCN's Professor Dan Laffoley said: "What these latest reports make absolutely clear is that deferring action will increase costs in the future and lead to even greater, perhaps irreversible, losses. The UN climate report confirmed that the ocean is bearing the brunt of human-induced changes to our planet. These findings give us more cause for alarm – but also a roadmap for action. We must use it."


  ocean heating


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