The Economist has written a fascinating special report on the alarming state of the world's oceans detailing:
- the decline in marine life
"The fish that once seemed an inexhaustible source of food are now almost everywhere in decline: 90% of large predatory fish (the big ones such as tuna, swordfish and sharks) have gone, according to some scientists. In estuaries and coastal waters, 85% of the large whales have disappeared, and nearly 60% of the small ones. Many of the smaller fish are also in decline. Indeed, most familiar sea creatures, from albatrosses to walruses, from seals to oysters, have suffered huge losses."
- the destruction of coral reefs
"Coral reefs, whose profusion of life and diversity of ecosystems make them the rainforests of the sea, have suffered most of all. Once home to prolific concentrations of big fish, they have attracted human hunters prepared to use any means, even dynamite, to kill their prey. Perhaps only 5% of coral reefs can now be considered pristine, a quarter have been lost and all are vulnerable to global warming."
- the increase in acidity due to the absorption of CO2 from the atmosphere
"The burning over the past 100 years or so of fossil fuels that took half a billion years to form has suddenly, in geological terms, put an enormous amount of carbon dioxide into the atmosphere. About a third of this CO2 is taken up by the sea, where it forms carbonic acid. The plants and animals that have evolved over time to thrive in slightly alkaline surface waters—their pH is around 8.3—are now having to adapt to a 30% increase in the acidity of their surroundings. Some will no doubt flourish, but if the trend continues, as it will for at least some decades, clams, mussels, conches and all creatures that grow shells made of calcium carbonate will struggle. So will corals, especially those whose skeletons are composed of aragonite, a particularly unstable form of calcium carbonate."
- the contamination of the waters with pesticides, heavy metals, radioactive matter and other poisons
"Man’s interference does not stop with CO2. Knowingly and deliberately, he throws plenty of rubbish into the sea, everything from sewage to rubber tyres and from plastic packaging to toxic waste. Inadvertently, he also lets flame retardants, bunker oil and heavy metals seep into the mighty ocean, and often invasive species too. Much of the harm done by such pollutants is invisible to the eye: it shows up only in the analysis of dead polar bears or in tuna served in New York sushi bars.
Increasingly, though, swimmers, sailors and even those who monitor the sea with the help of satellites are encountering highly visible algal blooms known as red tides. These have always occurred naturally, but they have increased in frequency, number and size in recent years, notably since man-made nitrogen fertilisers came into widespread use in the 1950s. When rainwater contaminated with these fertilisers and other nutrients reaches the sea, as it does where the Mississippi runs into the Gulf of Mexico, an explosion of toxic algae and bacteria takes place, killing fish, absorbing almost all the oxygen and leaving a microbially dominated ecosystem, often based on a carpet of slime."
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and the warming of the oceans, which risks reaching a catastrophic tipping point
"A hotter atmosphere has several effects on the sea. First, it means higher average temperatures for surface waters. One consequence for coral reefs is that the symbiosis between the corals and algae that constitute a living reef is breaking down. As temperatures rise, the algae leave or are expelled, the corals take on a bleached, white appearance and may then die. Warming also has consequences for ice: it melts. Melting sea ice affects ecosystems and currents. It does not affect sea levels, because floating ice is already displacing water of a weight equal to its own. But melting glaciers and ice sheets on land are bringing quantities of fresh water into the sea, whose level has been rising at an average of nearly 2 millimetres a year for over 40 years, and the pace is getting faster. Recent studies suggest that the sea level may well rise by a total of 80 centimetres this century, though the figure could plausibly be as much as 2 metres."
The Economist published eleven articles on the situation in the seas, all of which are interesting and informative. Why, one wonders, did the excellent editorial staff at The Economist not take position earlier?
To read the articles, click on the titles below.
from The Economist, December 30, 2008
