Ocean life faces mass extinctions, warns study

LIFE in the oceans is at imminent risk of the worst spate of extinctions in millions of years due to threats such as climate change and over-fishing, a study shows.

Time was running short to counter hazards such as a collapse of coral reefs or a spread of low-oxygen “dead zones”, according to the study led by the International Programme on the State of the Ocean (IPSO).

“We now face losing marine species and entire marine ecosystems, such as coral reefs, within a single generation,” according to the study by 27 experts to be presented to the United Nations.

“Unless action is taken now, the consequences of our activities are at a high risk of causing, through the combined effects of climate change, over-exploitation, pollution and habitat loss, the next globally significant extinction event in the ocean,” it said.

Scientists list five mass extinctions over 600 million years — most recently when the dinosaurs vanished 65 million years ago, apparently after an asteroid struck. Among others, the Permian period abruptly ended 250 million years ago.

“The findings are shocking,” Alex Rogers, scientific director of IPSO, wrote of the conclusions from a 2011 workshop of ocean experts staged by IPSO and the International Union for Conservation of Nature (IUCN) at Oxford University.

Fish are the main source of protein for a fifth of the world’s population and the seas cycle oxygen and help absorb carbon dioxide, the main greenhouse gas from human activities.

Jelle Bijma, of the Alfred Wegener Institute, said the seas faced a “deadly trio” of threats of higher temperatures, acidification and lack of oxygen, known as anoxia, that had featured in several past mass extinctions.

A build-up of carbon dioxide, blamed by the UN panel of climate scientists on human use of fossil fuels, is heating the planet. Absorbed into the oceans, it causes acidification, while run-off of fertilisers and pollution stokes anoxia.

“From a geological point of view, mass extinctions happen overnight, but on human timescales we may not realise that we are in the middle of such an event,” Bijma wrote.

The study said that over-fishing is the easiest for governments to reverse — countering global warming means a shift from fossil fuels, for instance, toward cleaner energies such as wind and solar power.

“Unlike climate change, it can be directly, immediately and effectively tackled by policy change,” said William Cheung of the University of East Anglia.

The report warned that damage to marine life would harm its ability to support humans, and that entire ecosystems, such as coral reefs, could be lost in a generation.

Dr Rogers, scientific director of IPSO, which convened the panel with IUCN, said: “The findings are shocking.

“As we considered the cumulative effect of what humankind does to the ocean the implications became far worse than we had individually realised.

“This is a very serious situation demanding unequivocal action at every level.

“We are looking at consequences for humankind that will impact in our lifetime and, worse, our children’s and generations beyond that.”

It said that some of the negative impacts of human activity, such as sea level rises and Arctic ice melt, were already matching “worst case scenario” predictions.

Those changes were compounding other problems, including alterations in harmful algae blooms and the loss of large, long-lived fish species which caused shifts in the food chain.

The scale of the combined impacts was greater than previously understood, they warned.

And the window of opportunity for taking action on problems such as greenhouse gas emissions was shrinking, they said.

“The world’s leading experts on oceans are surprised by the rate and magnitude of changes we are seeing,” said Dan Laffoley, senior advisor on marine science and conservation for IUCN and co-author of the report.

“The challenges for the future of the ocean are vast, but unlike previous generations we know what now needs to happen. The time to protect the blue heart of our planet is now, today and urgent.”

Three main drivers damaging the global marine environment

POLLUTION and global warming are threatening a mass extinction of marine life unseen for tens of millions of years, IPSO has warned.

Dying coral reefs, biodiversity ravaged by invasive species, expanding open-water “dead zones”, toxic algae blooms, the massive depletion of big fish stocks — all are accelerating.

All five mass extinctions of life on the planet, reaching back more than 500 million years, were preceded by many of the same conditions now afflicting ocean environments, they said.

Three main drivers are damaging the global marine environment, and all are a direct consequence of humans activity: global warming, acidification and a dwindling level of oxygen, a condition known as hypoxia.

Up to now, these and other impacts have been studied mainly in isolation. Only recently have scientists began to understand how these forces interact.

“We have underestimated the overall risks, and that the whole of marine degradation is greater than the sum of its parts,” Dr Rogers said. “That degradation is now happening at a faster rate than predicted.”

Indeed, the pace of change is tracking or has surpassed the worst-case scenarios laid out by the UN Intergovernmental Panel on Climate Change (IPCC) in its landmark 2007 report.

The chain reaction leading to increased acidification of the oceans begins with a massive influx of carbon into Earth’s climate system.

Oceans act as a massive sponge, soaking up more than a quarter of the CO2 humans pump into the atmosphere.

But when the sponge becomes too saturated, it can disrupt the delicately balanced ecosystems on which marine life — and ultimately all life on Earth — depends.

“The rate at which carbon is being absorbed is already far greater now than during the last globally significant extinction of marine species 55 million years ago,” when some 50% of deep-sea life was wiped out, the report said.

Pollution has also taken a heavy toll, rendering the oceans less resilient to climate change.

Run-off from nitrogen-rich fertiliser, killer microbes, and hormone-disrupting chemicals, for example, have all contributed to the mass die-off of corals, crucial not just for marine ecosystems but a lifeline for hundreds of millions of people too.

The harvesting up to 90% of some species of big fish and sharks, meanwhile, has hugely disrupted food chains throughout the ocean, leading to explosive and imbalanced growth of algae, jellyfish and other “opportunistic” flora and fauna.

Picture: Species under threat include giant black sea bass.