The response to the Deepwater Horizon oil spill in the Gulf of Mexico has, understandably for such a catastrophe, been huge -- from international condemnation of BP, to a narrowly avoided diplomatic row between Britain and the United States.

No one denies that the oil spill in the Gulf of Mexico is a disaster that is having a hugely damaging effect on ecosystems in the affected areas, as well as on the fishing and tourism industries. But how about a little sense of proportion?

Receiving somewhat less attention in the international press is the environmental outrage that has been inflicted on the Niger Delta over the past 50 years.

To give a recent example, on 1 May 2010, a ruptured ExxonMobil pipeline spilled more than a million gallons into the delta over seven days before the leak was stopped. There was not so much reporting about that.

This is just the tip of the iceberg. Though exact figures are hard to come by, because oil companies and the Nigerian government are secretive about oil spills, a 2006 report by WWF UK, the World Conservation Union, and Nigerian representatives found that up to 1.5 million tonnes of oil had been spilled in the area over the preceding 50 years. This is 50 times the amount spilled in the Exxon Valdez disaster in Alaska.

A 2009 report by Amnesty calculated that at least nine million barrels of oil had been spilled. These figures suggest that every year, an amount equivalent to that lost in the Gulf of Mexico is spilled in the delta.

The Nigerian National Petroleum Corporation says that an average of 300 individual spills each year equals nearly 2,300 cubic metres. This does not take into account "minor" spills, and the World Bank suggests that the real quantity is as much as ten times higher.

The delta is now one of the most polluted spots in the world. It is estimated that leaking crude oil -- which the oil companies blame on thieves and separatists, and campaigners blame on rusting equipment -- costs Nigeria $10m (£5.3m) daily.

The Niger Delta provides 40 per cent of all the crude oil imported by the United States. Over two generations, life expectancy in the region's rural communities -- where many people cannot get access to clean water -- has fallen to just over 40 years.

Barack Obama is right to recognise the scale of the disaster in the gulf (which, he said today, echoes the 11 September 2001 attacks), but it is rather sobering to note this disparity. Yet again, there seems to be one rule for the west, and another for the rest of the world.

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