The toxic sea

Each one of us dumps a tonne of carbon dioxide into the oceans every year, turning them into acidified soups — and threatening to destroy most of what lives in them

They are calling it “the other CO2 problem”. Its victim is not the polar bear spectacularly marooned on a melting ice floe, or an eagle driven out of its range, nor even a French pensioner dying of heatstroke. What we have to mourn are tiny marine organisms dissolving in acidified water.

In fact we need to do rather more than just mourn them. We need to dive in and save them. Suffering plankton may not have quite the same cachet as a 700-kilo seal-eating mammal, but their message is no less apocalyptic. What they tell us is that the chemistry of the oceans is changing, and that, unless we act decisively, the limitless abundance of the sea within a very few decades will degrade into a useless tidal desert.

In every way — economically, environmentally, socially — the effects of ocean acidification are as dangerous as climate change, and even harder to resist. It has been a slow dawning. Until recently, marine scientists have had little luck in engaging the public or political mind. The species most directly at risk — plankton, corals, sea snails, barnacles and other stuff that most people have never heard of — seemed as remote from our lives as cosmic dust. But now at last “the other CO2 problem” may have found a mascot of its own — the tiny but colourful clownfish, winsome star of the Disney classic Finding Nemo. In the film, Nemo gets lost. Now it turns out that real clownfish might lose their way too.

In early February, the American academic journal Proceedings of the National Academy of Sciences (PNAS) carried a paper titled “Ocean acidification impairs olfactory discrimination and homing ability of a marine fish”. The sombre language concealed a stark message. What the researchers had found was that clownfish larvae in acidified water were unable to detect the odours from adult fish that led them to their breeding sites. The implications were obvious. If the fish don’t breed, the species will not survive, and what is true for one species must be true for others. In time, the world’s fishing fleets will be less a food resource than a disposal problem.

What’s happening is this: the oceans absorb carbon dioxide (CO2) from the atmosphere. As most climate scientists and governments now agree, human activity — most importantly, burning fossil fuels — has intensified CO2 in the atmosphere, causing long-term climate change. The good thing is that the seas have absorbed a lot of the gas and so have slowed the pace of atmospheric warming. The bad thing is that CO2 reacts with sea water to make carbonic acid.

Since 1800, humans have generated 240 billion tonnes of carbon dioxide, half of which has been absorbed by the sea. On average, each person on Earth contributes a tonne of carbon to the oceans every year. The result is a rapid rise in acidity — or a reduction in pH, as the scientists prefer to express it — which, as it intensifies, will mean that marine animals will be unable to grow shells, and that many sea plants will not survive. With these crucial links removed, and the ecological balance fatally disrupted, death could flow all the way up the food chain, through tuna and cod to marine mammals and Homo sapiens. As more than half the world’s population depends on food from the sea for its survival, this is no exaggeration.

This is why 155 marine scientists from 26 countries recently signed the Monaco Declaration, identifying the twin threats of global warming and ocean acidification as “the challenge of the century”. It is, nevertheless, a challenge they have taken up only recently.

“The whole scientific community was caught with its pants down,” says Jason Hall-Spencer, research lecturer at Plymouth University, who was one of the signatories. The term “ocean acidification” was coined only in 2003 — by odd coincidence the same year Finding Nemo was released and 35,000 people died in the European summer heat wave — though, unlike global warming, it has not had to face the opposition of truth-deniers. Verging on panic in 2005, the Royal Society published a 68-page report in which it calculated that acidification had increased by 30% in 200 years. If we went on as we were, it said, this would rise to 300% by 2100, making the seas more corrosive than they had been at any time for hundreds of millennia. In every practicable sense, the damage was irreversible. “It will take tens of thousands of years for ocean chemistry to return to a condition similar to that occurring at pre-industrial times,” the Royal Society said.

It is a truism that might have been minted for the Darwin bicentenary. A species once lost is gone for ever. You can’t rewind evolution, or reinvent fish. We are not talking about dispossessing our children, or even our grandchildren’s grandchildren. We are talking so many generations into the fog of geological time that we might not even be talking about the same species. We are certainly not talking about low-lying countries protected by coral reefs, such as the Maldives. In future they will not be studying the marine environment: they will be part of it.

Doomy stuff like this, of course, is nothing new. The “warmists”, as the deniers like to call them, have been telling us for years that our rate of consumption is unsustainable and that future generations will pay a terrible price for our carelessness. If you don’t want to believe in climate change, you can argue that forecasts created by computer modelling are “theoretical”. Or you can confuse the long-term graph of “climate” with the short-term spikes of “weather”. Look, there’s a snowflake! Global warming can’t be happening!

But acidification permits no such equivocation. It is demonstrable, visible and measurable, and there is nothing theoretical about how it is caused or what it does. All the same, until now there has been one significant shortcoming.

As with the clownfish, it has been easy enough under laboratory conditions to see how individual species respond to acidity. What is much less easy is to observe the effects on entire ecosystems.

This problem has now been cracked by a team from Plymouth led by Jason Hall-Spencer, who scanned the world for a location where the sea conditions expected in future were already happening naturally. They found it in the Bay of Naples, just off the holiday island of Ischia.

The sea bed here is chalk. Deep geological activity converts some of this into carbon dioxide and forces it up through volcanic vents into the water. In and around the neighbourhood of these vents, the result is a perfect “gradient” of pH levels from the normal 8.1 all the way down to 7.4 (remember: the lower the pH, the higher the acidity). To non-scientists, the giving or taking of a few decimal points can look undramatic. To experts they mark the difference between life and death. The 30% increase in acidity during the industrial age is reflected by a drop in pH of just 0.1. On current trends, it will plummet by another 0.4 points to hit an unprecedented low of 7.7 by 2100. By 2300 it could be down to 7.3.

Few species living in the sea have experienced conditions like these at any time throughout their entire life on Earth. With pH as low as this, it is at least questionable that land creatures emerging from the primal swamp could have evolved into the bony specimens that roam the Earth today. And it is certain that the pace of environmental change is far too fast for evolution to keep in step. As a recipe for life on Earth, it is about as efficacious as nuclear war. Experiments have shown that the tipping point at which shell growth ceases comes at a pH of 7.8. This is the level which, on current trends, will be the global norm before the end of the century, and it is the level at which the Plymouth team has focused its attention.

Given all the dire warnings, the first visual impression at Ischia is something of a surprise. There are plenty of fish. Is it, then, a false alarm? Could the world’s scientists have got their statistical knickers in a twist and jumped to a false conclusion? Will life just go on as normal? Alas, no. The acidified water is a small zone in a wider sea. There is no barrier. The fish are just visitors. They come to feed on the soft-bodied algae that survive in the altered conditions, then they swim away again. What they don’t do is breed — which is exactly what the Nemo research predicts.

“Fish breed naturally at a pH of 8.1,” says Hall-Spencer. He believes the sensory loss observed in clownfish is only one part of the story. “Losing the sense of smell,” he says, “is not likely to be the only effect. It’s much more likely to be one impairment among many. Eggs in these conditions cannot develop normally.”

Shelled creatures in the Ischian waters are visibly suffering. Sea urchins thin out and disappear as the acidity increases; so do corals, limpets and barnacles. Sea snails straying into the zone have thin, weak shells, and produce no young. There is another important absentee, too — the coralline algae (seaweed with a chalk skeleton) that glues coral reefs together. Without it, reefs become weakened and fall apart.

In just a few decades, if the output of carbon dioxide does not abate, this will be the condition of all the world’s oceans. Many if not all commercially fished species, including shellfish, will suffer. So, too, will coral reefs, whose disintegration will leave low-lying coasts in the tropics unprotected from the rising seas and fiercer storms that climate change will unleash. By some calculations reefs will have vanished by 2065, and nobody expects them to survive into the 22nd century.

Nature, however, will continue to abhor a vacuum. Species that disappear will be replaced by alien invaders. Shelled and vertebrate creatures will be replaced by the soft and the blobby. Celebrity chefs, if they survive as a species, will be teaching us how to stuff jellyfish. The plant species that thrive around the volcanic vents in the Bay of Naples are alien to the Mediterranean, laying the foundations of an entirely different ecosystem.

Already, says Hall-Spencer, similar changes are occurring along the southern coasts of England. Oyster farmers and ships discharging ballast water have accidentally introduced Japweed, Sargassum muticum, a fast-growing brown seaweed that clogs beaches and harbours. Originally a native of southeast Asia and Japan, it is unfazed by low pH and almost impossible to eradicate. As in the classic case of the grey squirrel ousting the red, the invasive alien expels and replaces the natives.

“It perturbs the ecosystem and drives out things that should live there,” says Hall-Spencer. Plants are the base of the food chain, so everything in the water depends on them directly or indirectly. With the professional caution of the scientist, he declines to speculate on which species will be the first to disappear, but acknowledges that many creatures have little hope of survival.

To reprise the old Star Trek mantra, there will be life here, but not life as we know it.

Various ideas have been put forward to mitigate the damage and downgrade the outcome from fatal catastrophe to expensive nuisance. It will take some doing. One idea is “ocean fertilisation”, which involves adding iron to the water to stimulate a plankton bloom. The plankton then absorb atmospheric CO2 before sinking into deep water and locking the poison away.

Another scheme from the top shelf of academic fantasy is “ocean sequestration”, which involves sinking waste carbon into the deep ocean where, at depths in excess of 3.5 kilometres, the gas will solidify into crystals. A possibly more viable option is “geological sequestration”, though it is one that will whiten environmentalists’ hair. It involves “capturing” gas from industrial plants and injecting it into exhausted aquifers or worked-out oilfields, where it can be stored in the rock. Capacity is not a problem — the North Sea alone could hold as much as 800 gigatonnes, which is approximately 1,600 times the UK’s entire annual output of industrial carbon dioxide. Neither is the idea merely theoretical. The Norwegian oil and gas company Statoil pumps a million tonnes a year into a saline aquifer.

But the risks quite literally are incalculable. What happens if there is a leak? Drilling and extraction in the oilfields may well have caused subsidence and cracking in the rock. The idea makes no sense unless storage is safe, secure and “permanent” — which, in the case of CO2, means somewhere between 5,000 and 10,000 years, or about the same as some nuclear waste.

There is, of course, a fourth option, the simplest and yet hardest of the lot — changing the way we live. Carbon-reduction targets need to be more than just green baubles on the faraway policy tree. Greed has driven us to a level of over-consumption that threatens our health, melts the economy and progressively poisons the planet. Unless we can get a grip on ourselves, constrain our appetites and halt the mismatch between consumption and resources, the future is an empty ship sailing upon an empty sea.

Richard Girling, Times online, 8 March 2009. Article.

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