Scientists call it the "tipping point"; that measure beyond which natural systems fail. In the human body, this point is calculated at 107.6 degrees Fahrenheit. After that, brain damage occurs.
In the world's oceans, which exist in a precise equilibrium between 8 and 9 on the pH scale, this point is almost universally recognized as 7.8. After that, scientists agree, ecological systems begin to collapse and reversing the acidity will take thousands of years.
In order to understand why such an incremental difference should have such an enormous impact, it's important to understand pH, which is a measure of the acidity, or alkalinity, of fluids. The pH scale is condensed in a range from 0 - 14, with 0 acidic and 14 alkaline. Neutral is about 7, and this is the range in which living cells exist.
This scale is not only highly compact, but each unit of change is exponential. From 8 to 7 is not one degree more acidic, but ten times more acidic.
Elsewhere in nature, systems like human blood can mediate acidity to some extent through the exchange of potassium ions. Oceans don't have this capacity, as far as we know. Either that, or their absorption and sequestration of carbon dioxide - generated from the burning of fossil fuels (the primary cause of global warming) - has already passed a natural remediation point.
From this point on, scientists estimate, reduced pH in oceans will have drastic results in 100 years time. Already, increased ocean acidification along the Atlantic and Pacific coasts - exacerbated by additional emissions of sulfur dioxide and nitrogen oxides (NOx) - has led to a 30% reduction in species. The same thing is happening off the Western coast of Africa, the Middle East, around the Mediterranean, and off the coasts of China, to name just a few.
Some scientists, less sanguine, now suggest that the change may already be irreversible. If so, the entire oceanic food chain, from phytoplankton to whales, is in peril. Since humanity relies on the ocean for about 5% of its protein supply (a ratio likely to increase as earth's arable land is taken up feeding rising populations), the failure of the oceanic food chain will spell starvation to many. Perhaps even more significant is the fact that we already take more food than the oceans can supply, leading to decimated fish stocks, bans on fishing and - in rare cases - the loss of species because they can't reproduce fast enough.
Oceans, already 30% more acidic than they were at the beginning of the Industrial Revolution, continue to absorb carbon dioxide from burning fossil fuels at the rate of 22 tons a day. In spite of this dire scenario, spending to discover solutions remains at an all-time low. According to the nonprofit Kerzner Marine Foundation (KMF), the world spends $99 out of every $100 on land conservation, and only $1 on oceans, even though the oceans represent 70% of earth's surface area. This is why scientists, who originally thought carbon sequestration by oceans might be the solution to global warming, are only now waking up to the nightmare scenario of collapsing oceanic ecosystems which may already be beyond human repair. As Jason Hall-Spencer from the University of Plymouth notes, atmospheric concentrations of carbon dioxide are now so high that even a sharp curtailment of emissions wouldn't prevent further acidification.
"We've started it, and we can't stop it."
What happens when oceans become acidic? Carbon dioxide in water creates carbonic acid. This dissolves calcium carbonate, the component of everything from coral reefs to snail shells. Coral reefs are home to more than a quarter of all marine species; take out the reefs and ecosystems collapse. Mollusks like snails are the center of gravity of the ocean food web; take out the mollusks and everything fails in both directions. Meanwhile, plankton - which absorb carbon dioxide and fall to the bottom of the ocean, effectively sequestering the gas- are dying off because of a lack of iron in the water.
Geoengineering advocates propose dumping iron in the oceans to increase plankton growth and absorption. Opponents, many of them reputable scientists, argue that we don't know enough about the long-term effects of such projects to proceed, and suggest that we may inadvertently do more harm than good. Meanwhile, the reefs and mollusks die and the increasingly acidic oceans give rise to sea grasses, which thrive in the rising pH but don't offer much hope for feeding mankind in a future where too many people need too many resources to survive.
The Intergovernmental Panel on Climate Change (IPCC) says that, without cutting carbon dioxide emissions, ocean pH is likely to reach the tipping point, 7.8, by 2100. This is more acidic than the ocean has been in the last 800,000 years!
Because oceans create climate on a global scale, storing solar energy and transferring heat and cold via currents that communicate their temperatures to global wind patterns, the effects of ecosystem collapse in the oceans may have dire consequences on land, as well. Great Britain and Vancouver, British Columbia (Canada), which both enjoy rather balmy temperatures in spite of their latitude as a result of these wind patterns, might become frigid and uninhabitable (or unbearably hot) when the oceans can no longer store their burden of 118 billion tons of carbon dioxide and instead start releasing it into the atmosphere.
No one knows what the effects will be. In the meantime, those of us who sense an apocalypse building in the gradual deterioration of ecosystems wait and wonder if man himself will survive his depredations. Extinction is not impossible, and may be karmic retribution for failing to heed the warnings and curb an inordinate appetite for power.