If Life in the Ocean Perishes…

Posted by on set 6, 2011 in Corporate News | 0 comments

If Life in the Ocean Perishes…

Recently, I’ve become obsessed with our planet’s five mass extinctions, those rare events when three-quarters of the planet’s species vanish in a geological heartbeat.

The one that comes most readily to mind is the most recent, the Cretaceous, which ended 65 million years ago and took out the dinosaurs. But there were four before that–the Ordovician, Devonian, Permian, and Triassic–that did as much damage to the tree of life, or, in some cases even more, than the one that ended the reign of the Tyrannosaurus rex and his ilk.

I’m thinking about them for two reasons. The first is a preliminary report that came out in June from the International Programme on the State of the Ocean. This is a group of the planet’s top marine scientists who are compiling a comprehensive report on ocean health to be finished in 2012. Their initial findings, widely picked up by news organizations around the world, were grim.

The ocean’s health is in a “critical” state, the scientists found, the direct result of human activities. It’s so dire that we’ve actually begun to alter the basic chemistry of the ocean. That matters, the scientists said, because the ocean is one of the “key operating systems” of the planet. When we start to damage it, we’re hurting the planet’s ability to support life as it exists now. Put more starkly, if all life on land were to die tomorrow, life in the ocean would be fine. But if life in the ocean perished, so would life on land. Terrestrial species, including you and me, are dependent on life in the ocean for our own survival. Marine plankton produce every second breath of oxygen you breathe, to give just one example of the reasons we need to pay attention to what’s going on in the ocean.

The scientists pointed the finger at several human activities, each of which is getting far worse far more quickly than scientists had predicted. Some are obvious. We take out too many fish. We trawl across the ocean floor with heavy rigs leaving a wake of destruction, and then we pollute the waters when we take oil and gas out of the seabed. We dump sewage and industrial wastes into the waters creating dead zones with little or no oxygen, and introduce toxic new species to parts of the ocean that have no defenses against them.

One of the big threats they identify isn’t so obvious. That’s the phenomenon known as ocean acidification, a result of the high-carbon world we’ve created here on Earth. As we burn the fossilized remains of plants and animals that lived millions of years ago–coal, oil and gas–we’re releasing the ancient carbon stored in their bodies into today’s atmosphere in the form of carbon-dioxide gas. That’s why the concentration of CO2 has risen from 280 parts per million (ppm) (just under 0.03%) before the industrial revolution to 392 ppm today (just under 0.04%).

A level that high is unusual. We know it hasn’t been above 300 ppm for 20 million years.

And it would be far higher except that the ocean is absorbing a great deal of that ancient carbon, roughly a third of what’s been emitted since we started burning fossil fuels for industry about a quarter of a millennium ago. But while the gas is inert (if heat-trapping) in the atmosphere, it is chemically reactive in the ocean, making carbonic acid. We’ve put so much ancient carbon into the atmosphere, and therefore into the ocean, that we’ve altered the pH of the global ocean. Today, it’s 30% more acidic than it was before industrialization, and more acidic than it’s been in about 55 million years.

This basket of threats means that if we do nothing to reverse these trends, the world’s ocean “is at a high risk of entering a phase of extinction of marine species unprecedented in human history,” the scientists conclude.

And that’s where the second piece of my obsession comes in. I’ve been reading a paper recently published in Nature: “Has the Earth’s sixth mass extinction already arrived?” by Anthony Barnosky and several collaborators.

The authors have a handy table on the paper’s first page, describing the five mass extinctions, when they happened, how long the die-offs took, how many species were winked out. Opposite these descriptions is a list of the reasons scientists have been able to reconstruct for the extinction spasms.

In each case, changes to ocean chemistry were thought to be key factors. And what’s the answer to the question the paper poses? The authors conclude that another catastrophic mass extinction is imminent within just a few centuries “if current threats to many species are not alleviated.”

“It may be of particular concern that this extinction trajectory would play out under conditions that resemble the ‘perfect storm’ that coincided with past mass extinctions,” the authors write.

The difference between now and the past extinctions, is, of course, that our hand is on this trigger. Unlike in the past, when brutal planetary change came about as continents shifted, mountain ranges emerged, tectonic plates moved around, and asteroids hit, today, the change is simply the cumulative effect of human activity.

The logical next step is to stop the activity that is putting life on the planet–undoubtedly including billions of humans–at risk. It seems to me that this is a policy-maker’s dreamtime, with the biggest stakes of any phase of our species’ short span on the planet.

Alanna Mitchell

Source: ssppjournal.blogspot.com

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