Why Disasters Are Getting Worse

In the space of two weeks, Hurricane Gustav has caused an estimated $3 billion in losses in the U.S. and killed about 110 people in the U.S. and the Caribbean, catastrophic floods in northern India have left a million people homeless, and a 6.2-magnitude earthquake has rocked China's southwest, smashing more than 400,000 homes.

If it seems like disasters are getting more common, it's because they are. But some disasters seem to be affecting us in worse ways — and not for the reasons you may think. Floods and storms have led to most of the excess damage. The number of flood and storm disasters has gone up 7.4% every year in recent decades, according to the Centre for Research on the Epidemiology of Disasters. (Between 2000 and 2007, the growth was even faster, with an average annual rate of increase of 8.4%.) Of the total 197 million people affected by disasters in 2007, 164 million were affected by floods.

It is tempting to look at the lineup of storms in the Atlantic Ocean (Hanna, Ike, Josephine) and, in the name of everything green, blame climate change for this state of affairs. But there is another inconvenient truth out there: We are getting more vulnerable to weather mostly because of where we live, not just how we live.

In recent decades, people around the world have moved en masse to big cities near water. The population of Miami-Dade County in Florida was about 150,000 in the 1930s, a decade fraught with severe hurricanes. Since then, the population of Miami-Dade County has rocketed 1,600%, to 2,400,000.

So the same-intensity hurricane today wreaks all sorts of havoc that wouldn't have occurred had human beings not migrated. (To see how your own coastal county has changed in population, check out this cool graphing tool from the National Oceanic and Atmospheric Administration.)

If climate change is having an effect on the intensities of storms, it's not obvious in the historical weather data. And whatever effect it is having is much, much smaller than the effect of development along coastlines. In fact, if you look at all storms from 1900 to 2005 and imagine today's populations on the coasts, as Roger Pielke Jr., and his colleagues did in a 2008 Natural Hazards Review paper, you would see that the worst hurricane would have actually happened in 1926.

If it happened today, the Great Miami storm would have caused from $140 billion to $157 billion in damages. (Hurricane Katrina, the costliest storm in U.S. history, caused $100 billion in losses.) "There has been no trend in the number or intensity of storms at landfall since 1900," says Pielke, a professor of environmental studies at the University of Colorado. "The storms themselves haven't changed."

What's changed is what we've put in storms' way. Crowding together in coastal cities puts us at risk on a few levels. First, it is harder for us to evacuate before a storm because of gridlock. And in much of the developing world, people don't get the kinds of early warnings that Americans get. So large migrant populations — usually living in flimsy housing — get flooded out year after year. That helps explain why Asia has repeatedly been the hardest hit area by disasters in recent years.

Secondly, even if we get everyone to safety, we still have more stuff in harm's way than ever before. So each big hurricane costs more than the big one before it, even controlling for inflation.

But the most insidious effect of building condos and industry along water is that we are systematically stripping coasts of the protection that used to cushion the blow of extreme weather. Three years after Katrina, southern Louisiana is still losing a football field's worth of wetlands every 38 minutes.

Human beings have been clearing away our best protections all over the world, says Kathleen Tierney, director of the Natural Hazards Center at the University of Colorado, Boulder. "The natural protections are diminishing — whether you're talking about mangrove forests in areas affected by the Indian Ocean tsunami, wetlands in the Gulf Coast or forests, which offer protection against landslides and mudslides."

Before we become hopelessly lost in despair, however, there is good news: we can do something about this problem. We can enact meaningful building codes and stop keeping insurance premiums artificially low in flood zones.

But first we need to understand that disasters aren't just caused by FEMA and greenhouse gases. Says Tierney: "I don't think that people have an understanding of questions they should be asking — about where they live, about design and construction, about building inspection, fire protection. These just aren't things that are on people's minds."

Increasingly, climate change is on people's minds, and that is for the better. Even if climate change has not been the primary driver of disaster losses, it is likely to cause far deadlier disasters in the future if left unchecked.

But even if greenhouse gas emissions miraculously plummet next year, we would not expect to see a big change in disaster losses. So it's important to stay focused on the real cause of the problem, says Pielke. "Talking about land-use policies in coastal Mississippi may not be the sexiest topic, but that's what's going to make the most difference on this issue," he says.