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

IUCN report warns that ‘truly staggering’ rate of warming is changing the behaviour of marine species, reducing fishing zones and spreading disease
Oliver Milman The Guardian 5 Sep 16;

The soaring temperature of the oceans is the “greatest hidden challenge of our generation” that is altering the make-up of marine species, shrinking fishing areas and starting to spread disease to humans, according to the most comprehensive analysis yet of ocean warming.

The oceans have already sucked up an enormous amount of heat due to escalating greenhouse gas emissions, affecting marine species from microbes to whales, according to an International Union for Conservation of Nature (IUCN) report involving the work of 80 scientists from a dozen countries.

The profound changes underway in the oceans are starting to impact people, the report states. “Due to a domino effect, key human sectors are at threat, especially fisheries, aquaculture, coastal risk management, health and coastal tourism.”

Dan Laffoley, IUCN marine adviser and one of the report’s lead authors, said: “What we are seeing now is running well ahead of what we can cope with. The overall outlook is pretty gloomy.

“We perhaps haven’t realised the gross effect we are having on the oceans, we don’t appreciate what they do for us. We are locking ourselves into a future where a lot of the poorer people in the world will miss out.”

The scale of warming in the ocean, which covers around 70% of the planet, is “truly staggering”, the report states. The upper few metres of ocean have warmed by around 0.13C a decade since the start of the 20th century, with a 1-4C increase in global ocean warming by the end of this century.

The ocean has absorbed more than 90% of the extra heat created by human activity. If the same amount of heat that has been buried in the upper 2km of the ocean had gone into the atmosphere, the surface of the Earth would have warmed by a devastating 36C, rather than 1C, over the past century.

At some point, the report says, warming waters could unlock billions of tonnes of frozen methane, a powerful greenhouse gas, from the seabed and cook the surface of the planet. This could occur even if emissions are drastically cut, due to the lag time between emitting greenhouse gases and their visible consequences.

Warming is already causing fish, seabirds, sea turtles, jellyfish and other species to change their behaviour and habitat, it says. Species are fleeing to the cooler poles, away from the equator, at a rate that is up to five times faster than the shifts seen by species on land.

Even in the north Atlantic, fish will move northwards by nearly 30km per decade until 2050 in search of suitable temperatures, with shifts already documented for pilchard, anchovy, mackerel and herring.

The warming is having its greatest impact upon the building blocks of life in the seas, such as phytoplankton, zooplankton and krill. Changes in abundance and reproduction are, in turn, feeding their way up the food chain, with some fish pushed out of their preferred range and others diminished by invasive arrivals.

With more than 550 types of marine fishes and invertebrates already considered threatened, ocean warming will exacerbate the declines of some species, the report also found.

The movement of fish will create winners and losers among the 4.3 billion people in the world who rely heavily upon fish for sustenance. In south-east Asia, harvests from fisheries could drop by nearly a third by 2050 if emissions are not severely curtailed. Global production from capture fisheries has already levelled off at 90m tonnes a year, mainly due to overfishing, at a time when millions more tonnes will need to be caught to feed a human population expected to grow to 9 billion by 2050.

Humans are also set to suffer from the spread of disease as the ocean continues to heat up. The IUCN report found there is growing evidence of vibrio bacterial disease, which can cause cholera, and harmful algal bloom species that can cause food poisoning. People are also being affected by more severe, if not more numerous, hurricanes due to the extra energy in the ocean and atmosphere.

Coral reefs, which support around a quarter of all marine species, are suffering from episodes of bleaching that have included three-fold in the past 30 years. This bleaching occurs when prolonged high temperatures cause coral to expel its symbiotic algae, causing it to whiten and ultimately die, such as the mass mortality that has gripped the Great Barrier Reef.

Ocean acidification, where rising carbon dioxide absorption increases the acidity of the water, is making it harder for animals such as crabs, shrimps and clams to form their calcium carbonate shells.

The IUCN report recommends expanding protected areas of the ocean and, above all, reduce the amount of heat-trapping gases pumped into the atmosphere.

“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,” said Inger Andersen, director general of the IUCN.

Warming oceans are 'sick,' global scientists warn
Kerry Sheridan Yahoo News 5 Sep 16;

Global warming is making the oceans sicker than ever before, spreading disease among animals and humans and threatening food security across the planet, a major scientific report said on Monday.

The findings, based on peer-reviewed research, were compiled by 80 scientists from 12 countries, experts said at the International Union for Conservation of Nature (IUCN) World Conservation Congress in Hawaii.

"We all know that the oceans sustain this planet. We all know that the oceans provide every second breath we take," IUCN Director General Inger Andersen told reporters at the meeting, which has drawn 9,000 leaders and environmentalists to Honolulu.

"And yet we are making the oceans sick."

The report, "Explaining Ocean Warming," is the "most comprehensive, most systematic study we have ever undertaken on the consequence of this warming on the ocean," co-lead author Dan Laffoley said.

The world's waters have absorbed more than 93 percent of the enhanced heating from climate change since the 1970s, curbing the heat felt on land but drastically altering the rhythm of life in the ocean, he said.

"The ocean has been shielding us and the consequences of this are absolutely massive," said Laffoley, marine vice chair of the World Commission on Protected Areas at IUCN.

- Microbes to whales -

The study included every major marine ecosystem, containing everything from microbes to whales, including the deep ocean.

It documents evidence of jellyfish, seabirds and plankton shifting toward the cooler poles by up to 10 degrees latitude.

The movement in the marine environment is "1.5 to five times as fast as anything we are seeing on the ground," Laffoley said. "We are changing the seasons in the ocean."

The higher temperatures will probably change the sex ratio of turtles in the future because females are more likely to be born in warmer temperatures.

The heat also means microbes dominate larger areas of the ocean.

"When you look overall, you see a comprehensive and worrying set of consequences," Laffoley said.

More than 25 percent of the report's information is new, published in peer-reviewed journals since 2014, including studies showing that global warming is affecting weather patterns and making storms more common.

The study includes evidence that ocean warming "is causing increased disease in plant and animal populations," it said.

Pathogens such as cholera-bearing bacteria and toxic algal blooms that can cause neurological illnesses such as ciguatera poisoning spread more easily in warm water, with direct impact on human health.

"We are no longer the casual observers in the room," Laffoley said.

"What we have done is unwittingly put ourselves in the test tube where the experiment is being undertaken."

- Cut greenhouse gases -

Meanwhile, the hotter oceans have killed off coral reefs at an unprecedented rate, reducing fish species by eliminating their habitats.

The loss of reefs cuts down on the abundance of certain fish, with implications for food security.

"In Southeast Asia, harvests from marine fisheries are expected to fall by between 10 percent and 30 percent by 2050 relative to 1970-2000, as the distributions of fish species shift," said the report.

The report highlights the need for swift action on renewable energies, experts said.

"We need to cut greenhouse gases," said Carl Gustaf Lundin, director of the global marine and polar program at IUCN.

"There is no doubt in all our minds that we are the cause of this," he added.

"We know what the solutions are. We need to get on with it."

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