The big shift: oceans and sustainability

Rapid coastal urbanisation is having a profound impact on the world’s oceans and their sustainability. With Expo 2012 in Yeosu focusing on this theme when it kicks off this month, John Vidal highlights the growing need to protect this vital ecosystem

It's called "the big shift". From Australia to Senegal and China to Brazil, millions of people are moving annually to live near oceans. Nearly half the world's population including 14 of the world's largest megacities, now live within a two-hour drive of the sea and if trends continue, says the UN, this could double by 2025.

The ecological effect of rapid coastal urbanisation has helped to devastate the world's oceans, says the UN Environment Programme. Unless this is controlled, the result will be more over-fishing and marine litter, the further loss of wetlands and biodiversity and the destruction of mangrove forests and coral reefs.

Fragile ecosystem

The fragility of the oceans and the urgent need to protect them will be the focus of Expo 2012 in the coastal Korean city of Yeosu this summer. Here, 106 countries and nine international organisations will pledge to protect them for the future survival of the world. The 20 million expected visitors will hear how oceans have been used as a rubbish dump for years. "Once thought to be so vast and resilient that no level of human insult could damage them, they are now crying out for attention,” says the Washington-based Worldwatch Institute.

The UN's Food and Agriculture organisation will tell Expo visitors that more than half of all wild fish stocks are fully exploited, and 17% are over-exploited; coral reefs, vital for fish breeding and marine diversity, have suffered alarmingly from over-fishing and deforestation and “dead zones” caused by the run-off of chemicals and farming fertilisers have caused over 150 large marine areas to suffer life-suffocating low oxygen levels.

But slowly, the world is waking up to the fact that the oceans are fundamental to all life and that marine pollution does not respect national borders. Waste which enters the ocean has been found to turn up anywhere in the world. In 1992 a container ship in the Pacific Ocean lost 30,000 plastic ducks off the coast of China. These ducks have now turned up as far away as Australia, Greenland and the United Kingdom.

Plastic litter, swept out to sea, now threatens all marine species.  The Swiss-based Save our Seas foundation estimates that there are around 250 billion pieces of plastic – most practically invisible to the human eye – suspended in circulation in the Mediterranean alone. Plastic breaks down in the sea into minute polymers and currents swirl these nearly invisible bits of plastic around vast areas. The "Great Pacific Garbage Patch", in the northern Pacific has been estimated to be the size of the continental USA and is one of five vast areas of plastic pollution circulating in ocean currents, or "gyres".

Marine protection zones

Governments, pressure groups and cities are beginning to fight back. Calls are growing for a network of marine protection zones and the EU is expected to pass laws next year to force countries to halve the amount of marine litter dumped in European waters.

The International Union for Conservation of Nature estimates there are nearly 6,000 marine conservation areas, covering over two million square kilometres of ocean. But the vast majority are very small, and strict enforcement occurs on only 0.08 per cent of ocean.

"Protecting the world's wetlands, mangroves and coral reefs – before it is too late – is critical. Just as national parks conserve our lands, marine reserves can help ensure ocean health for generations to come," says a spokesman for the Pew Environmental trust, which aims to establish a worldwide system of very large, highly protected marine reserves where fishing and other extractive activities are prohibited.

National targets

Many countries have now established national targets to protect the oceans. Australia has proposed a one million square kilometre marine park in the Coral Sea, Britain has designated 500,000sq km "no-take" area in the Indian Ocean, while Indonesia has promised to protect 200,000sq km by 2020. Madagascar, Jamaica and others have pledged to protect 20 per cent of their territorial waters.

Cities are beginning to act, too. Most coastal cities in developing countries have no sewage systems. Mumbai is leading the way in India by spending US$300m on a system that will dispose of 80 per cent of the sewage currently flowing untreated into the sea. China is investing in massive waste plants.

"The oceans sustain us – we depend on them for food security, for livelihoods, for economic growth – for fostering the 'blue economy'. But our marine ecosystems, are fragile and under threat. A sustainable future will depend on healthy oceans and ecosystems," said Sha Zukang, head of the Department of Economic and Social Affairs, which is responsible for this year's 20-year follow up to the Rio Earth Summit.