Worst Environmental Disaster Ever. Really?

On one hand we have BP executives, Rush Limbaugh, and various Southern politicians saying the Gulf oil contamination from the Deepwater Horizion disaster is no big deal. The Gulf is a big place, nature will clean itself up, and you won't be able to tell anything ever happened there in a few years. On the other hand, we have oil industry critics and environmentalists saying it is indeed a big deal and that the leak will cause permanent damage to the ecologies and economies of the US Gulf coast. And then we have this:

If even BP’s backup plans fail, it would cause a pollution disaster "heretofore unseen by humanity," said one expert.

It is this rapidly accelerating realization that is giving BP’s attempt Wednesday to cap the well new political and environmental urgency.

The worst-case scenario is hoped and believed to be a continued flow of 5,000 barrels per day, and by some estimates vastly more, until August, when BP completes “relief wells” to intercept the damaged well.

But, experts say, there are no sure things when operating equipment a mile under the water and 13,000 feet below the ocean floor.

Professor Tad Patzek, who heads the Department of Petroleum and Geosystems Engineering at the University of Texas-Austin, gives the relief well a 90 percent chance of success. But he’d rather not consider the other 10 percent.

"As a petroleum professional, I don’t even admit the possibility that that might be possible," he said when asked about a failure to stop the flow. "That would be an environmental disaster of a caliber that was heretofore unseen by humanity."

Keep in mind, this is not the ranting of a tree-hugging granola-head (like me); it is the professional opinion of someone within the oil industry. I think any one left of Limbaugh will agree that if we don't manage a permanent closure of the well, the environmental impact of the leak will be orders of magnitude beyond anything we've been able to watch on our teevees in recent years, but will it be "an environmental disaster of a caliber that was heretofore unseen by humanity?" I have no doubt that Mr. Patzek is a first rate engineer and geologist, but how does he rate as an historian? Has humanity ever witnessed a worse environmental disaster?

Ignoring the human economic impacts, here are some worst-case, long-term environmental impacts that leap to my mind:

• As the crude hits the beaches and soaks into the coastal marshlands, it will render the majority of that area unfit for most animal life. These marshlands are made up of several unique ecologies. As they die, a number of species will likely go extinct.
  
• The beaches are birthing grounds for endangered sea turtles and the marshes are a vital stop on the paths of many migratory bird species. Again, a blow like this could cause several extinctions and, at a minimum, will add a severe new pressure to the survivor species' life cycles.
  
• If the marsh grasses die, the barrier islands will wash away exposing the wetlands to sea storms and dramatic erosion all along the coast.
  
• In the sea, the oil has contaminated the entire water column, not just the top or bottom.
  
• The microbes that will slowly digest the oil on the seabed, suck up vast amounts of oxygen, creating anoxic (oxygen free) zones where virtually no life is impossible.

I'm sure I missed a lot, but these are the main points that I can think of. In short, the oil is going to create a dead zone that will extend, in places, dozens of miles inland and as far as two hundred miles off shore. The coastline itself will change in certain areas. Several species are already threatened with extinction by the leak. The longer the well leaks, the worse the local effects will be and the further afield it will spread.

That's pretty bad, but is it the worst environmental disaster humanity has ever witnessed? Right off the top of my head, global warming seems to be a real contender in that contest. Our part in the end-Pleistocene extinction of mammoths and other megafauna could be another contender. Any others? Leave your suggestions and arguments in the comments. The only rules I'll set are that the disaster has to have been clearly environmental in nature, that it must arguable have been human caused, and that it must have happened in the last fifty thousand years or so. Feel free to argue for other or different rules.