Science in Society Archive

I-SIS Special Miniseries
Save Our Oceans, Save Our Planet

Oceans in Distress

Pollution, destructive overfishing and increasing commercial exploitation are threatening the planet’s cradle of life, warns the UN. Dr. Mae-Wan Ho

Overfishing and pollution

Pollution and overfishing are damaging the oceans, especially the deep oceans, the United Nations warns in a new report [1-3]. Time is running out to save them, and urgent legislation is required to halt this wanton destruction of the planet’s “cradle of life”.

More than 90 percent of the earth’s living biomass (weight of living matter) is found in the oceans, and 90 percent of that is made up of single cell and microbial species. With 90 percent of the oceans yet to be explored, the scale of devastation already happening has become all too obvious

In 2005, 84.5 million tonnes of fish were taken from the world’s oceans, 100 million sharks and related species were butchered for their fins, 250 000 turtles got tangled up in fishing gear and 300 000 seabirds including 100 000 albatrosses were killed by illegal long-line fishing. Nineteen out of 21 albatross species are now threatened with extinction.

During the same period, 6.4 million tonnes of litter was thrown into the oceans, and 38 000 pieces of discarded plastic float on every square kilometre. There are up to 6 kg of marine litter to every kg of plankton.

Just one percent of the world’s 3.5 million fishing boats are large industrial vessels, but they trawl 60 percent of all the fish caught on the planet. Industrial fishing has depleted the world’s stock of tuna, cod, swordfish and marlin by as much as 90 percent in the last century.

Adding to the strain on the ocean’s fish stocks, the UN estimated that nearly $10 billion worth of fish are caught illegally each year, up to 30 percent taken from unregulated waters.

The water temperature has risen while its alkalinity fell from soaking up extra carbon dioxide. The coral reefs off Australia and Belize are dying, and newly discovered cold-coral reefs in the Atlantic have already been destroyed by bottom-trawling fishnets.

The UN report covers a wide-range of human activities damaging the oceans including naval sonic radar exercises that kill whales in droves.

Kristina Gjerde, high seas policy adviser of the International Conservation Union’s global marine programme, who wrote the report, said, “Once limited largely to shipping and open ocean fishing, commercial activities at sea are expanding rapidly and plunging ever deeper.”

Deep-sea fishing has more than doubled from five percent of total world catches in 1992 to almost 11 percent in 2002. Deep-water species tend to grow slowly and to have long life cycles; and when over-exploited or destroyed by commercial activities, they take a long time to recover if at all. The deep-sea fish orange roughy matures at around 32 years. A specimen found was approximately 240 years old. Deep-sea fisheries typically peak in less than 5 years and collapse within 15 years. The unregulated orange roughy fishery in the Southwest Indian Ocean collapsed in less than 4 years.

Other commercial exploitation expanding

Other commercial exploitations of the deep oceans are also expanding. Twenty to 30 percent of the oil used in the United States comes from the Gulf of Mexico Outer Continental Shelf, but 50 percent of leased acreage in the Gulf of Mexico is in deep water. A first exploratory well has been drilled in water over 3 000 m deep. Seven of the top 20 oil fields in the US are now located in federal deep-water areas.

What the report hasn’t said is that as global warming thaws the polar ice caps, oil giants are looking to prospect for oil and gas under the Arctic Ocean [4] (How to be fuel and food rich under climate change).

As there is no international agreement over the area, it is a free for all. Territorial disputes have been growing between the eight countries with a claim to the Artic: Russia, USA, Canada, Norway, Denmark, Sweden, Greenland and Iceland.

A string of new exploitations of the deep oceans is in train, from deep seabed mining, bio-prospecting for microbes with commercial interests, carbon storage by injecting carbon dioxide into deep seawater or under the seabed, and siphoning deep ocean waters up for air-conditioning, aquaculture, etc.(The blue revolution: air conditioning and energy from deep waters of lakes and oceans, this issue). All threaten the fragile, biodiverse deep-sea communities to different degrees. At least half of the species there remain to be identified, many unique to each of the deep trenches or underwater mounts, not to mention the hydrothermal vents at 450 C harbouring some of the fastest growing and extremely rare species on earth that thrive on chemical energy rather than depend on photosynthesis for their food.

Climate change makes conservation efforts all the more important, as 60 percent of the marine world lies beyond the limits of national jurisdiction and is vulnerable to commercial exploitation. Achim Steiner, executive director of the UN’s environment programme called on governments to develop guidelines, rules and actions that are urgently needed to protect the rich biodiversity of our oceans.

Pollution, overfishing and commercial exploitation are not the only threats our oceans face. There are signs that marine life is failing right at the bottom of the food web as the result of global warming, which could set in train a series of aggravating feedback effects on climate change (Oceans and global warming, Oceans carbon sink or source? this series).

We must save our oceans now to save our planet:

Article first published 20/07/06


  1. Gjerde KM. Ecosystems and Biodiversity in Deep Waters and High Seas, UNEP Regional Seas Report an Studies No. 178,  UNEP/IUCN, Switzerland, 2006.
  2. “World’s oceans reaching point of no return, says UN”, Sam Knight, Times online, 16 June 2006,,,3-2229211,00.html
  3.  “Pollution, overfishing destroying oceans”, David Adam, The Hindu, 19 June 2006,
  4. “Global warming sparks a scramble for black gold under retreating ice”, David Adam, The Guardian 18 April 2006.

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