5 September 2016: The International Union for the Conservation of Nature (IUCN) has released a review on ocean warming that suggests it may “be the greatest hidden challenge of our generation." The review, launched at IUCN's World Conservation Congress (WCC) in Honolulu, Hawai'i, US, stresses the extent and scale of ocean warming on the world's ecosystems and human well-being, from direct and indirect effects on fish stocks to increased risk to water-borne diseases and extreme weather events.

'Explaining Ocean Warming: Causes, Scale, Effects and Consequences,' examines the effects of ocean warming on ecosystems and species alongside the benefits oceans provide to humans. The review describes the effects of ocean warming on coral reefs, noting that warming oceans are causing fish to move to cooler waters and damaging fish habitats in other areas, which is projected to result in reduced catches, particularly in tropical regions. Under a business as usual greenhouse gas (GHG) emission scenario, marine fisheries harvests in Southeast Asia are predicted to decrease by 10 to 30% by 2050 as fish species' distributions shift as a result of ocean warming. Globally, entire groups of species, including plankton, jellyfish and fish, are predicted to move up by ten degrees of latitude to keep up with ocean warming, while seabirds and turtles will lose their breeding grounds.

IUCN stresses that ocean warming is “no longer a single story of ocean warming challenges to coral reefs, but a rapidly growing list of alarming changes across species at ecosystem scales, and across geographies spanning the entire world.” IUCN Director General Inger Andersen said, “The only way to preserve the rich diversity of marine life, and to safeguard the protection and resources the ocean provides us with, is to cut GHG emissions rapidly and substantially.” One of the report's lead authors, Dan Laffoley, stresses the ocean's role in absorbing 93% of the heat from human-induced warming since the 1970s “comes at a price” to entire ecosystems. The report underlines that this regulating function of the oceans happens at the cost of profound alterations to the ocean's physics and chemistry that lead especially to ocean warming and acidification, and consequently sea-level rise.

The report finds that the protection oceans and their ecosystems offer against climate change is “likely to reduce as the ocean warms” and that changes in the ocean happen between 1.5 to five times faster than on land. It report urges recognition of the severity of ocean warming impacts on ecosystems and of the benefits oceans provide to humans. It recommends, inter alia: expanding marine protected areas (MPAs); introducing legal protection in areas beyond national jurisdiction (ABNJ); and addressing gaps in knowledge, including through better evaluation of the economic and social risks associated with warming oceans. The report further recommends“rapidly and substantially” reducing GHG emissions.

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Soaring ocean temperature is 'greatest hidden challenge of our generation'