Climate Change

Ocean warming leading to loss of fish stocks, crop yields: IUCN

The report, compiled by 80 scientists across 12 countries, highlights evidence of impacts on marine life, from microorganisms to mammals

By Rajeshwari Ganesan
Published: Monday 05 September 2016
Ocean warming is already affecting ecosystems from polar to tropical regions, driving entire groups of species towards the pole. Credit: Patrick Clan /Flicker

In a report released at the IUCN World Conservation Congress in Hawaii today, it has stated that the effects of ocean warming are now more visible than ever and it is affecting humans in direct ways and the impacts are already being felt. “From effects on fish stocks and crop yields to more extreme weather events and increased risk from water-borne diseases, global warming is here for real,” says the report, ‘Explaining ocean warming: Causes, scale, effects and consequences.’

Ocean conservation is one of the major themes addressed by the ongoing IUCN Congress, where IUCN members will vote on motions related to protecting the high seas and protected areas in Antarctica, among others.

Findings of IUCN report

The report reviews the effects of ocean warming on species, ecosystems and on the benefits oceans provide to humans. It has been compiled by 80 scientists across 12 countries and highlights detectable scientific evidence of impacts on marine life, from microorganisms to mammals, which are likely to increase significantly even under a low-emissions scenario.

In a media statement, IUCN director general Inger Andersen said, “Ocean warming is one of this generation’s greatest hidden challenges—and one for which we are completely unprepared. 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 greenhouse gas emissions rapidly and substantially.”

The report states, “Ocean warming is already affecting ecosystems from polar to tropical regions, driving entire groups of species such as plankton, jellyfish, turtles and seabirds up to 10 degrees of latitude towards the poles, causing the loss of breeding grounds for turtles and seabirds, and affecting the breeding success of marine mammals.”

With fish habitats disappearing and fish species migrating to cooler waters, the tropical regions will face a major fall in fish catch.

“In Eastern African countries and the Western Indian Ocean, for example, ocean warming has reduced the abundance of some fish species by killing parts of the coral reefs they depend on, adding to losses caused by overfishing and destructive fishing techniques. In South-East Asia, harvests from marine fisheries are expected to fall by between 10 per cent and 30 per cent by 2050 relative to 1970-2000, as the distributions of fish species shift, under a high ‘business as usual’ greenhouse gas emission scenario,” the report states.

Impact of ocean warming on crop yields

Not only fish, the warming oceans are also affecting the weather. “The impact has already been felt on crop yields in important food-producing regions such as India and North America, where the ocean warming has led to an increased rainfall in mid-latitudes and monsoon areas, and less rain in various sub-tropical regions. The number of severe hurricanes has increased at a rate of around 25-30 per cent per degree of global warming,” the report adds.

While oceans are known to absorb the heat emitted from global warming, it comes at a heavy price, warn experts. “Since the 1970s, the oceans have absorbed most of the heat from human-induced warming since the 1970s—a staggering 93 per cent, acting as a buffer against climate change. We were astounded by the scale and extent of ocean warming effects on entire ecosystems made clear by this report,” says Dan Laffoley, marine vice chair of the World Commission on Protected Areas at IUCN, and one of the lead authors.

“There has been strong evidence to suggest that ocean warming is causing an increased disease in plant and animal populations and also impacting human health, as the pathogens spread easily in warmer waters, including cholera-causing bacteria and harmful algal blooms that cause neurological diseases like ciguatera. The protection against climate change offered to us by oceans and their ecosystems—such as absorbing large amounts of CO2 and sheltering us from storms and erosion—is also likely to reduce as the ocean warms,” says the report.


The report’s recommendations include recognising the severity of ocean warming impacts on ocean ecosystems and the benefits they provide to humans, expanding marine-protected areas, introducing legal protection for the high seas, better evaluating the social and economic risks associated with warming oceans and continuing to fill gaps in scientific knowledge, as well as cutting greenhouse gas emissions rapidly and substantially.

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