Here's some alarming perspective on big disastrous spills. Over the past 50 years, Shell and other companies have spilled an estimated 1.5 million tons of oil into the Niger Delta ecosystem. That's the equivalent of one Exxon Valdez accident per year, every single year, for five decades.

And this isn't just some long-gone problem that's now been fixed. Last year, Shell reported losing some 14,000 tons of crude around Nigeria, double what made its way into the delta in 2008. That was largely due to thieves damaging a wellhead and militants bombing a pipeline, but the amount is staggering no matter what the cause. And it underscores the point that banning new offshore drilling in the United States without doing anything about our underlying oil addiction doesn't really solve the environmental problem—it just pushes production to places like Nigeria, where devastating spills are a regular fact of life.

(Flickr photo credit: Amnesty International)