We're watching the Cedar River inundate most of Cedar Rapids and other parts of Iowa at this very moment. A few months ago, we watched Typhoon Nargis flood most of Burma's Irrawaddy delta. And in 2005, we watched Hurricane Katrina inundate New Orleans and a tsunami of legendary proportions wash over lands all over South Asia. Between these highly-publicized disasters, and others covered less thoroughly, hundreds of thousands of lives have been lost, tens or hundreds of billions of dollars in damage have been done, and human misery beyond estimation has been wreaked.

It's tempting to dismiss all of this as the cruelty of Nature, the sort of unforeseeable disaster that comes out of nowhere and gobsmacks us all. Unfortunately, that temptation may be in error, and humans may shoulder more of the blame than we'd care to admit. That's the thrust of comments made by Kamyar Enshayan, a professor at Northern Iowa University, who believes that Iowa's current flooding is attributable not to uncontrollable nature, but to over-development in floodplains, destruction of wetlands that historically absorbed and blunted floods, and the development of farm fields too close to rivers and streams.

These factors make it more likely that rainwater will be immediately delivered to rivers, rather than absorbed by soil and wetlands and slowed down enough that catastrophic floods are less likely. The river that receives it is more likely, furthermore, to be heavily sedimented, its capacity reduced.

"We've done numerous things to the landscape that took away these water-absorbing functions," Enshayan said. "Agriculture must respect the limits of nature."

Mary Skopec, a water quality expert for the state of Iowa, was more specific: "We've lost 90 percent of our wetlands."

This pattern repeats itself in the clearing of mangrove swamps in Burma, allowing the unmitigated force of Nargis' storm swell to race up the Irrawaddy delta, and the clearing and draining of Louisiana's coastal wetlands. The wholesale development of almost every area suitable for building or agriculture has deprived us of critical free "services" that ecosystems provide us - such as flood mitigation.

We can't control the weather, tectonic plates, or tides. We can, and should, however, wisely manage and maintain the defenses that intact, healthy ecosystems can provide us. Is it possible that the consequences of myopic policies, overly-intensive management, and overly-intensive agriculture are more costly than the short-term economic benefits they provide? Enshayan, and a growing number of other environmental policy experts, believe so.

Looking forward to a future where natural disasters are forecast to be exacerbated by global warming, it behooves us to consider how to avoid compounding our suffering with unnatural disasters of our own making.