Millions are without power in Florida after Irma—one of the most powerful Atlantic hurricanes on record—swept through the state this weekend before weakening to a tropical storm. It caused its fair share of damage, but Florida’s most ominous fears did not play out; extremely vulnerable eastern coastal areas, including Miami, were spared the worst.

But meteorologist and disaster risk expert Stephen Strader says the state is still in a very dangerous position, due to intense population growth and overdevelopment of its low-lying coastal zones. He predicts it is only a matter of time before another storm devastates the Sunshine State and some of its major cities. And he adds that it is not the only state facing this threat: Overdevelopment and expanding populations across the U.S. mean natural disasters now pose a greater risk to many other places, such as Houston and Oklahoma City.

Scientific American spoke with Strader, an assistant professor of geography and the environment at Villanova University, about why Florida and many other places now face a graver risk from natural disasters—and what officials, developers and the public can do to address the problem.

[An edited transcript of the interview follows.]

You research risk and disaster potential in storm-vulnerable areas. What have you discovered about places like Florida?
A few years ago, Walker Ashley at Northern Illinois University and I started developing this idea called the expanding bull’s-eye effect. It basically says that as cities grow and there are more people, we’re seeing increased disaster potential—more and more people are being affected by disasters.

Florida is a perfect example of where we’re seeing this expanding bull’s-eye effect. We’ve seen a building up of lands in vulnerable or risky areas, starting in the 1920s with Miami Beach. We’ve seen high-rises built on barrier islands, which are the first to be affected by hurricanes. We’ve seen developers take out marsh and swamp land and fill it in, and create areas of dry land to build homes and other structures. All this has resulted in Florida increasing its odds of disaster over time, because we shouldn’t be in these locations. Ultimately, when we look at disasters it’s not always about how strong the hurricane, tornado or wildfire is—it’s also about how society is changing to influence disaster potential.

How does climate change play into this problem?
What we are trying to tease out is, which has a greater effect: society or changing hazards because of climate change? Climate change is affecting our hazards, but at the same time society has also increased its ability to be [harmed] by a hazard as well. So these two issues are coming together more and more often, resulting in disasters like we’ve seen with Irma and Harvey, and out West with the wildfires. What we’re finding out is that hazard plays a role, but societal growth is much more important—not necessarily in terms of how bad the impacts are but how frequent the impacts might be.

What’s happened along our coast, in Florida and Houston as well as all the way up the coast into [North Carolina’s] Outer Banks, is we’ve seen growth in coastal population. You can imagine if the worst hurricane on record went through, say, Miami Beach in 1900, it wouldn’t affect as many people. Now there are 20 times more people in Miami Beach, and that’s going to make the impact much worse. The societal effects are something we also need to consider in the future as the climate changes.

You have said that overdevelopment, population growth and poor planning have made Miami and southern Florida a “ticking time bomb.” What do you predict will happen in this region?
Disaster amnesia is a real thing. Take 1992, with Hurricane Andrew: It devastated parts of Miami and Coral Gables. However, we seem to have forgotten what happened and started building right back to where we were before. As long as we keep filling up natural wetlands and marshes, building [expensive] hotels and resorts in these areas prone to hurricanes, it’s only a matter of time before a hurricane creates another disaster in this area worse than Hurricane Andrew. We see this in a number of places along the coast—the hubris of humans building in locations that are extremely vulnerable to storm surge or wind hazards.

Are these same issues also occurring in other parts of the U.S.?
Houston is a good example of a city that has had unchecked urban sprawl. The natural areas around that city are coastal prairie, which are very good at soaking up lots of water. [Developers] replaced that with concrete, and created a concrete jungle where the water has nowhere to go. We saw this exacerbate flooding in Houston [during Hurricane Harvey]. We’ve seen this issue with not just tropical storms but also with tornadoes in places like Oklahoma City—it is one of the highest tornado-prone regions in the country. We’ve seen urban sprawl in every location across the U.S.

What's the best way for forward for places like Houston and Miami?
The logical choice here is to have better zoning and land-use practices. But more importantly, when we do build structures, we need to make them extremely wind-resistant, flood-resistant—whatever it may be. We need to build them to the best building codes possible. Those are the protective measures we can take—little things on the engineering side can go a long way in protecting people and buildings from extreme damage.

With hurricanes in places like Miami, we can simply stop building on wetlands or barrier islands, which are very risky locations for people to be. The damage that can occur with storms can be astronomical. We can keep people from building in these locations—or if they do build there, make them pay their true risk in terms of flood insurance.

Would it be better for these regions to just retreat to low-lying coastal lands? If so, how do you get people to do that?
In a perfect world, people wouldn’t live right against the coast—we’d live a mile or two inland. Unfortunately, about 39 percent of the U.S. population lives in a coastal county. It’s unrealistic to say developers will stop building. They’re not going to move Miami or Houston. So you have to think of protective measures in terms of engineering solutions, communication and getting people to evacuate.

What will it take to change the minds of officials and the public about how Florida and other coastal areas should be developed?
The only thing that will change our minds is to have an extremely bad disaster. We sort of dodged a bullet here—not to speak unempathetically about the people who were affected by Irma—but if Irma had been a category 5 into the heart of Miami, that would have been the worst-case scenario, where you’re putting insurance companies out of business and there’s tons of loss of life. It will take something on the scale of [Hurricane] Katrina or larger to change the public’s mind.