Summary: The environmentalist community has put their resources into fighting anthropogenic global warming. For reasons discussed in other posts, that campaign has achieved few of the political gains sought. Meanwhile the prosaic forces of commerce destroy the oceans through pollution and and overfishing. We can do better.
From CNN, by David McNew/Getty Images
The clock is running; we have been warned by articles such as this:
“Overfished and under-protected: Oceans on the brink of catastrophic collapse“, CNN, 27 March 2013
The Census of Marine Life, a decade-long international survey of ocean life completed in 2010, estimated that 90% of the big fish had disappeared from the world’s oceans, victims primarily of overfishing.
Tens of thousands of bluefin tuna were caught every year in the North Sea in the 1930s and 1940s. Today, they have disappeared across the seas of Northern Europe. Halibut has suffered a similar fate, largely vanishing from the North Atlantic in the 19th century.
In some cases, the collapse has spread to entire fisheries. The remaining fishing trawlers in the Irish Sea, for example, bring back nothing more than prawns and scallops, says marine biologistCallum Roberts, from the UK’s York University. “Is a smear of protein the sort of marine environment we want or need? No, we need one with a variety of species, that is going to be more resistant to the conditions we can expect from climate change,” Roberts said.
The situation is even worse in Southeast Asia. In Indonesia, people are now fishing for juvenile fish and protein that they can grind into fishmeal and use as feed for coastal prawn farms. “It’s heading towards an end game,” laments Roberts.
Trawling towards disaster
One particular type of fishing, bottom-trawling, is blamed for some of the worst and unnecessary damage. It involves dropping a large net, around 60 meters-wide in some cases, into the sea and dragging it along with heavy weights from a trawler.
Marine conservationists compare it to a bulldozer, with the nets pulled for as far as 20km, picking up turtles, coral and anything else in their path. The bycatch, unwanted fish and other ocean life thrown back into the sea, can amount to as much as 90% of a trawl’s total catch.
Upwards of one million sea turtles were estimated to have been killed as by catch during the period 1990-2008, according to a report published in Conservation Letters in 2010, and many of the species are on the IUCN’s list of threatened species.
Campaigners, with the support of marine scientists, have repeatedly tried to persuade countries to agree to an international ban, arguing that the indiscriminate nature of bottom-trawling is causing irreversible damage to coral reefs and slow-growing fish species, which can take decades to reach maturity and are therefore slow to replenish their numbers.
“It’s akin to someone plowing up a wildflower meadow, just because they can,” says Roberts. Others have compared it to the deforestation of tropical rainforests.
Bottom-trawling’s knock-on impacts are best illustrated by the plight of the deep-sea fish, the orange roughly (also known as slimeheads) whose populations have been reduced by more than 90%, according to marine scientists. Orange roughys are found on, or around, mineral-rich seamounts that often form coral and act as feeding and spawning hubs for a variety of marine life.
“Anywhere you go and try to harvest fish with a trawl you are going to destroy any coral that lives there, and there is example after example of the damage that is done by trawlers,” says Ron O’Dor, a senior scientist on the Census of Marine Life. “If I ruled the world, they would be banned, they’re just such a destructive method of catching fish. Fishermen have other methods, such as long-line, that cause far less damage.
“The disturbing truth is that humans are having unrecognized impacts on every part of the ocean, and there is much we have not seen that will disappear before we ever get a chance,” says O’Dor, who is also a professor of marine biology at Dalhousie University in Halifax, Canada.
For more see “Net gains: Estimating the scale of the problem may allow us to arrest dangerous levels of overfishing“, Nature, 20 February 2013.
Why have activists focused so much on global warming over other issues? Perhaps because as a vehicle it offered more leverage to make political and social changes they seek. As David Hume learned at the Radical Emission Reduction Conference at the Royal Society.
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