The Black Sea is the world's most isolated sea. For any ship to reach the oceanic expanses of the Atlantic it has to first pass through the 700 metre-wide Bosphorus strait, then plot its way through the Dardanelle strait into the Aegean Sea, before traversing the entire length of the Mediterranean to reach the exit point at Gibraltar. If a home relied on such a constricted drainage system, it would cause any plumber inspecting it to suck their teeth with alarm.

It is with great sadness, then, that the full scale of the oil tanker spill over the weekend in the Black Sea is now becoming apparent. We know that a violent storm has already caused one tanker carrying 4,000 tonnes of fuel oil to split and sink. There are also reports of another oil tanker developing cracks, as well as two ships carrying sulphur sinking. A dozen or so members of the crews are reported dead or missing. This perfect storm may well have led to the "perfect" environmental disaster - a series of potential vulnerabilities conspiring to converge at the wrong place, at the wrong time.

The Black Sea has been causing frowns of deepening concern among environmentalists for many years. Eutrophication is deemed the sea's biggest headache - with three of Europe's major rivers emptying into the Black Sea, nitrogen and phosphorus fertiliser from the continent's farms have been pouring into the waters for decades, resulting in an "anoxic dead zone" in the north-western section of the sea. Over-fishing, as ever, is also a big problem.

The nations that face onto the Black Sea have made some attempts over the years to unite and forge a treaty that would better protect the sea - the so-called Bucharest convention was signed in 1992 - but, as with most efforts to nurse maritime areas back to health, commercial and national interests have suppressed any real progress.

The prevailing attitude we have towards the world's oceans and seas is that they are there for us to exploit - for food, for gas and oil, and for transporting goods. We still largely see them as an infinite resource to exploit. Equally, we use them to dump our rubbish and effluent. This is reflected in the utterly woeful protection we grant them under current maritime law aimed at governing shipping, as overseen by the International Maritime Organisation, a United Nations special agency based in a grey building just opposite Westminster on the River Thames in London. And even where there are sensible regulations in place, many ships sidestep them by sailing under "flags of convenience".

For example, the IMO's first convention to address the environmental impact of shipping - known as Marpol - was born out of the Torrey Canyon tanker spill off the coast of Cornwall in 1967. But it took 16 years before it actually came into force on the high seas. Even then it only dealt with oil. It wasn't until 1988 that a ban on dumping plastics at sea came into force. And it still remains the case today that a ship simply has to make sure that it's 12 nautical miles or more from shore (some nations, such as the US, have introduced tougher rules within their own territorial waters) before it can offload its "operationally generated" waste overboard. If a ship shreds the waste into pieces smaller than 25 millimetres, this restriction falls to just three nautical miles. Similar rules apply to sewage, which for a cruise ship carrying thousands of passengers and crew can add up to a considerable volume each day.

Over the years, there have been calls to set up international maritime parks - vast stretches of deep ocean that are given the same environmental status and protection as places onshore such as Yosemite, Dartmoor or the Serengeti. So far such attempts have largely failed, or been restricted to areas close to shore - last year the Papahanaumokuakea Marine National Monument in Hawaii became the world's largest maritime protected area, larger even than Australia's Great Barrier Reef Marine Park. (By comparison, the UK's government has stuttered over introduced laws aimed at protecting our seas. The recent Queen's speech again failed to mention a draft marine bill that was promised in the Labour party's 2005 election manifesto. And, yet, at the same time it announces its intention to lay claim to potential resource-rich territorial waters in the Antarctic.)

Disasters such as the oil spill this week in the Black Sea usually elicit the same response. The sight of seabirds dripping in sticky black oil, or sandy beaches cast thick with tar, sadden us all. But we have been witnessing such sights for decades and still little meaningful action is ever taken to protect the seas from our excesses and carelessness. In the US, a group called the Blue Campaign Movement is seeking to mobilise citizens - known as "seaweed" activists, as opposed to grassroots activists - across the country to campaign for an American Oceans Act to protect "our public seas". Surely, an international movement seeking similar, pan-oceanic goals needs to now be mobilised.

Leo Hickman writes the weekly ethical living column for the Guardian. He is the author of A Life Stripped Bare and A Good Life.

© 2007 The Guardian