06/27/2010 09:51 pm ET Updated May 25, 2011

The Oil Spill Catastrophe: Biggest Ever? Not Close.

The National Mississippi River and Aquarium in Dubuque, Iowa, has opened a huge tank with water, and artificial coral, and see-through stickers on the window that look like oil...and nothing else. No fish or plants or birds. Just lifeless water, to show what the catastrophe in the Gulf of Mexico looks like.

Bravo to the folks who want us to appreciate what this disaster is doing to the marine environment! They are also perfectly demonstrating something else... that the psychology of risk perception often gets in the way of risk reality, at our peril. The oil spill is a catastrophe, but risks that are catastrophic scare us more than risks that are chronic, even though in many cases, the chronic risks are far bigger threats.

Catastrophes have three unique affective qualities that feed our fears. The American Heritage Dictionary defines catastrophe as "A great, often sudden calamity." (Emphasis is mine.) A catastrophe has to be big, it has to happen all at once, and something about it has to be calamitous, unusual and really bad. All three things are absolutely true about the BP's Deepwater Horizon oil spill.

But every year, the marine life in the same part of the Gulf of Mexico is choked to death in the "dead zone," an area that gets so rich in fertilizer run-off carried by the Mississippi River from the agricultural middle of America, that gigantic mats of algae bloom and then suck the oxygen out of the water as they die and decay, and so much oxygen is consumed that there isn't enough left in the water for anything else. The only things left alive in an area as big as 8,000 square miles are single-celled organisms.

And this happens every year. But where are the headlines about that? Where are the network newscasts live from the shores, and environmentalist outcry and Tweets and demands for government action and displays of the Dead Zone in aquariua? Marine biologist Sylvia Earle frets that the oil gushing into the Gulf of Mexico could "create another dead zone". Yes, but what about the annual dead zone!? Why doesn't that chronic risk get the same attention?

Because chronic risks don't hit us in the gut the way a "catastrophe" does. The dead zone is not sudden, like an oil spill, or an industrial accident, or a plane crash. And unfortunately, it's not some sort of unusual calamity. It happens all the time. So it's like regular murder compared to mass murder, or the gradual disaster of climate change compared to single event environmental catastrophes like Chernobyl or Bhopal, or dozens of daily deaths in car crashes compared to one plane crash. The chronic risks may be bigger, but they don't feel that way. The large scale, sudden calamity rings our alarm bells louder, which the media senses and feeds, compounding the awareness of and fear about catastrophic sorts of risks.

Consider what that does to overall public and environmental health. The Gulf of Mexico dead zone is one of dozens that occur along populated coastal areas around the world all the time. And fertilizer runoff-fed dead zones are only one of the profound harms we're constantly doing to the marine environment. Carbon dioxide pollution is acidifying the oceans and killing coral reefs, along with climate change, by warming the water. We're destroying basic food supplies with overfishing, we ravage the benthic (bottom) environment with steel-netted drag trawlers.

But while we demand that BP pay to clean up the oil spill, are we demanding that the agricultural industry pay for the dead zones their fertilizer use creates? Are we demanding that food companies put billions in escrow accounts to pay for the damage that unsustainable fishing practices cause? Are we demanding that fossil fuel burning be taxed to pay for the environmental damage it does? Are we demanding the government do more about any of these things? A little, maybe, but not nearly like we're jumping all over BP and the government for the Deepwater Horizon mess. We call them externalities, not catastrophes, and these far greater harms persist, in large measure because they just don't upset us as much as catastrophes do.

In How Risky Is It Really? Why Our Fears Don't Always Match the Facts, I call this The Perception Gap, the gap when we're too afraid of some lesser risks or not afraid enough of some bigger ones, and that creates a danger in and of itself. We do have to fear fear itself... too much or too little. And the catastrophic nature of some risks, as bad as such events can be, is one of the reasons we sometimes get the big risk picture wrong.