IRA FLATOW: This is “Science Friday.” I’m Ira Flatow. You’ve heard the predictions. Temperatures are increasing. Glaciers are melting at alarming rates. Sea levels could rise as much as six feet in the next century, according to the IPCC. What does this mean though for people living on the coast? What are the costs? We always hear about the costs of doing things. What about the cost of not doing things? And how many people will be affected?

Well, there is a new study out that talks about the rising tide that could force, how many? 13.1 million people from their homes, forcing them to flee to higher ground. And the price tag for that migration comes out to $14 trillion. That’s trillion with a T. That’s according to a study out this week in the journal Nature Climate Change.

And how many local communities, how may they use this information to prepare? My next guest is one of the authors on that study. Jason Evans, Assistant Professor of Environmental Sciences at Stetson University in DeLand, Florida. Welcome to “Science Friday.”

Yeah. Hi there. Thank you so much, Ira.

IRA FLATOW: You’re welcome. There are many studies out that have looked at how coastal residents would be affected by sea level change. Your estimate is two to three times higher. How did you come to this number?

JASON EVANS: So what we did, Ira, is we just had kind of a simple observation. So living in a place like Florida, which is where I live– and I’ve watched over the past 20, 30 years, people move into these areas along the coastlines, rapid growth. And what we realized is that this growth, this ongoing that we’re still moving in these areas, has not been factored in.

And so we decided that, OK, let’s go out and see if we can actually look at population growth. And so we came up with a way of doing that, and that’s the reason why– and as it turns out, there’s a lot of people that are moving into coastal areas. And if you factor in this growth, it’s basically on a collision course when thinking about sea level rise. And so that’s the reason why we came up with these much higher estimates.

IRA FLATOW: So this estimate assumes that business is going to go ahead as usual over the decades, that people will continue to move in.

JASON EVANS: Well, that’s exactly right. And so we think about if you go to somewhere like Miami Beach– I just happened to be there last weekend– and we’re seeing things like adaptation, as well. So we don’t actually assume that people are going to move necessarily. We actually very carefully talk about impact, then also things like adaptation actions, and then the cost of these. And so we know that $300 million is right now being spent in Miami Beach on things like pumps and elevating roads.

And so with each community that’s along the coast, and as we’re making decisions about growth, what we really want this study to do– it’s kind of a way of really driving into that conversation. How much is it going to cost? How much risk is there to people to live in these very vulnerable areas? And for infrastructure that we build, how much is it going to cost to maintain it? So that’s really what the study is really intended to look at.

IRA FLATOW: That’s a lot of money, $14 trillion. There are localities, states, building these figures into their budgets, knowing that they’re going to be flooding.

JASON EVANS: They are increasingly. And so it’s really case-by-case as we start seeing the early impacts. And so we talk about king tides a lot. These are the annual high tides that we see each year. And these are very natural occurrences, but as we see with sea level rise, now the king tide that, say, 30 years ago would have just been a minor problem, now you have water going into the streets. In some areas we actually see things like storm sewers run the wrong way.

And so once you start seeing this, that’s when you really get the attention of, say, the local governments. And then we’re starting to do studies to say, OK, how much is it going to cost to adapt? And it becomes very, very case-by-case. So some places are. Some people are not. But we hope that this information is going to help in terms of this conversation.

IRA FLATOW: Is there any evidence that– nature is flexible. It can adapt. Is there any evidence that some of the ecosystems and the natural landscapes might adapt to the sea level change?

JASON EVANS: Well, there is actually evidence of that. As a matter of fact, there’s actually some work that came out just this week as well in Nature Climate Change that was looking at, in fact, things like coastal marshes and dune fields that are along the coast. They actually can respond. And so what we were really looking at is, OK, when we actually build into areas in terms of humans– and we can also adapt. We can build dikes. We can elevate. But terms of nature itself, it does have a natural sort of resilience.

And so this is some of the more exciting work in terms of thinking about sea level rise and also climate change, is how can we work with these systems? And what’s also very good about things like coastal marshes and mangroves is they’re extremely productive, and they also are kind of a negative feedback in terms of taking a lot of carbon in. So it’s very important, thinking about how we can really protect and maintain these ecosystems so that way they can be kind of our ally.

IRA FLATOW: But you have to work in communities that believe that this is a real thing happening. I mean, isn’t North Carolina– isn’t there a law that restricts the kinds of sea level rise projections policymakers can use to protect their communities?

JASON EVANS: Well, there was some legislation. And I think it got a little bit unfairly tarred by the end. They are actually now looking at sea level rise again in North Carolina. As a matter of fact, I work in North Carolina. There is planning that’s happening there, as well. I’ve actually worked with farmers in Hyde County, North Carolina. They have saltwater that’s coming in on their fields. And then so they do know that sea level rise is a real thing, and so there is planning that’s happening up there in North Carolina.

Again, it’s, where do we see these impacts? And then there are kind of local factors, things like subsidence, as well, that certain areas that are starting to see it sooner– of areas that we see impacts, there’s a lot of work that’s being done trying to understand it.

IRA FLATOW: You can’t deny what your eyes are seeing, is what you’re saying?

JASON EVANS: That’s exactly right. And that’s the work in the Florida Keys. I worked on there. And then when you see a king tide and you have water that’s on a street with saltwater, it’s very hard to say, this isn’t a problem. And again, Miami Beach– as I say, southeast Florida has really been one of the leaders.

So they’re very much looking at climate change, and really confronting it head-on, because we know southeast Florida is the area, in terms of just the sheer amount of people, this is a very consistent result, is just the most vulnerable within the entire United States. And so there, there’s not much of a this-isn’t-a-problem. It’s more of a bipartisan sort of consensus down there that this is a problem that we really need to deal with.

IRA FLATOW: Well, we hope the politicians believe that, too when they start talking about Florida. As you say, they talk about southeast Florida as ground zero for climate change.

JASON EVANS: That’s exactly right. That’s exactly right. And then we see that. We do see that. And then really, political science is its own beast. So I try to stay just in the environmental science field, but yeah. But I think that we’re starting to see the tide turn. The pun, I did not mean.

IRA FLATOW: That’s a good pun. No, it fits right in. Thank you, Jason. We’ve run out of time. But $14 trillion and 13 million people– it’s an interesting study. Thanks for being on the show with us today.

JASON EVANS: Great. Thank you so much, Ira.

IRA FLATOW: You’re welcome. Jason Evans is an Assistant Professor of Environmental Sciences at Stetson University in DeLand, Florida.

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