Talking Sea Level Rise

James G. Titus is generally recognized as the principal advocate for preparing for accelerated sea level rise in the United States. His publications include the first reports to project future sea level rise, the first estimates of the cost of sea level rise and maps depicting the land that will be inundated, and the first legal analysis of mechanisms to enable wetlands to migrate inland as the sea rises He is a member of the Maryland Bar and project manager for sea level rise at the US EPA. In this interview with CA-CP he shares his expertise and outlook, developed over the course of more than two decades hands-on work at the EPA, on global warming-induced sea level rise.

Let’s start with the basics. One of the projected and increasingly-evident impacts of global warming is sea level rise. The rise in sea level is brought on by thermal expansion (as water warms it increases in volume), melting of glaciers and melting of Greenland’s ice sheet. How great an effect are we talking here?

JT: A one to three foot rise in average global sea levels, which is considerably better news than the two- to three- meter rise scientists were forecasting twenty years ago. That said, the U.S. Atlantic and Gulf coasts are more vulnerable to sea level rise than other places in the world, both because the land is very flat, and because it is sinking. The land is sinking as a result of both natural geological influences and human ones (isostatic rebound resulting from the retreat of glaciers at the end of the last ice age, and land subsidence due to extraction of oil and water).

So when you talk about sea level rise to people, is it about mitigating climate change, adapting to what we already know is coming – or some combination of the two?

JT: I focus on the causes, effects, and adaptation to sea level rise. And for many audiences, I try to uncouple global warming from sea level rise. Within the most vulnerable coastal states, especially Florida, Texas, Louisiana, and North Carolina, many people reject the premise that greenhouse gases will probably accelerate sea level rise in sea level, but agree that they need to do something about the current rise in sea level--and even the possibility that it may accelerate. So I come in and say: here is the data on the current trend, here is a map of all the low-lying land--you need to do something. And global warming is one more reason to do something. Impacts and adaptation are closely related, so it makes sense for the same person to talk about both. Emissions reduction is a separate topic.

Now the term "adaptation" seems to mean three different things to different people. First, there are those who are mostly interested in the grand question about whether we enact policies to reduce emissions. Some of those folks think we have to choose between adaptation and mitigation. We have those who think that if in fact global warming does have serious impacts, we can rely on technology to adapt, instead of reducing emissions. Others in that group oppose adaptation for largely the same reason, fearing that adaptation diverts the message away from the true solution. A second group of people--which include most scientists and other middle-of-the-road people who say that no matter what we do about greenhouse gases, we are going to see some global warming, so we have to look at adaptation seriously, from a cost-benefit analysis, and do what we need to do. To those folks, adaptation is compatible with emission reduction.

Then there are those who mainly deal with the consequences of sea level rise, not the question about whether or not we mitigate. This is basically where I’m spending most of my time these days. The shores are eroding, floods are getting higher, wetlands are encroaching on farms and front yards. The Mayor of a small coastal community has to deal with these issues. For these folks, it is not a question of whether to adapt, but how to adapt. People who oppose adaptation are no friend to the coastal zone, or any of the near-term victims of climate change.

What do you mean by "adaptation"?

JT: Adaptation involves tens of thousands of individual decisions that reach a different result because the sea is rising. But those decisions fall into three fundamental pathways: A) hold back the sea with walls (and lose the habitat), B) elevate your coastal property and possibly even the habitat, or C) migrate inland.

People are adept at using technology to adjust to changes in their surroundings; we usually go with plan A or B. In low-lying areas, we are seeing a lot of homes being elevated after recent storms. In eroding areas with higher ground, a structure that stops the erosion is more common. Even when you elevate, there are some planning and infrastructure issues. You need to elevate the street, but that might cause someone's yard to flood unless they elevate first, but if you wait for the last house to elevate before bringing up the street, then the street may be impassable in an emergency--but we really hate to force someone to elevate their yard. But if their yard floods it will have standing water, mosquitoes--a public health problem. This is all manageable if there is a coherent plan--and that's why coastal communities need to think about sea level rise now.

My fear, however, is that the human tendency to dig in and adjust prevents ecosystems from being able to successfully cope with sea level rise, because the response of a natural ecosystem to dramatic changes is generally that third option, migration. So our current approach puts human settlements and natural ecosystems on a collision course, and we’re seeing intertidal habitat being squeezed out as a result.

We protect our wetlands by not letting people build on them. But because we are ignoring the fact that the sea is rising and shores are retreating, in the long run, we are going to end up with the same wetland loss as if we had allowed people to build on them. The only difference is that we can blame it on the sea, not the development. That doesn't make much difference to a horseshoe crab or sea turtle.

The following cartoon summarizes the situation. We protect our wetlands by not letting people build on them. But because we are ignoring the fact that the sea is rising and shores are retreating, in the long run, we are going to end up with the same wetland loss as if we had allowed people to build on them. The only difference is that we can blame it on the sea, not the development. That doesn't make much difference to a horseshoe crab or sea turtle.

So coastal habitats like wetlands are vulnerable?

JT: The estuarine beaches are most vulnerable, because they are often ten or twenty feet wide. Put a structure inland of a beach, and the beach may be gone in 10-20 years. Tidal marshes may last longer. If the spring tide range is 6 feet, then most wetlands are less than three feet above mean sea level. So the sea will have to rise three feet to inundate them at mean tide--and wetlands can keep pace with sea level rise to some extent. So in these areas where we are building just inland of large expanses of wetlands, it may take a century or so before they are mostly lost. But many coastal areas have only a 2-foot tidal range, so the sea will not have to rise as much to drown them. In those areas where the dry land remains undeveloped, there is a good chance that some wetlands will survive indefinitely. Of course, there are complicating factors even there---it depends partly on how the land is being used before it is inundated.

I’ve heard a term brought up in discussion of land conservation and I’m hoping you can explain it to me: What are "rolling easements"?

JT: A rolling easement is a legal arrangement in which the public's right (or the right of a private conservancy) to see the wetlands and beaches migrate inland as shores retreat, takes precedence over the desire of the shorefront land owner to hold back the sea. This can be accomplished as a type of conservation easement, as a "reversionary interest in land", or by regulation. You can think of it as a free-market alternative to a setback policy or large-scale governmental purchase of coastal land. Under a rolling easement policy, the private land owners assume the risk of sea level rise. Under the current policy, the coastal environment assumes the risk. Incidentally, the general term came out of the common law of Texas. People drive on the beaches, and so if the shore erodes, a single house could block the transportation route. The courts found that no one could have assumed that their home took precedence over the public right to traverse the beach, and hence that public easement to the beach is a "rolling easement" that goes inland as the shore erodes. The rule does not apply along wetland shores, only some of the beaches along the Gulf of Mexico.

Can you give us a pragmatic reason why global-warming induced sea level rise matters?

JT: You have the right to beach your boat on any beach--even Maine and Massachusetts where property owners have title down to mean low water. If there is no beach, that's impossible. Also, water quality depends on healthy wetlands. And, in terms of biodiversity, many species of finfish and shellfish depend on marshes for part of their life cycle. Migratory birds depend on horseshoe crab eggs, which the crabs lay mainly on estuarine beaches.
The problem of global warming-related sea level rise is probably less urgent in New England than the rest of the US Atlantic Coast. The coastal land is much higher [in New England]. You have northeasters, but you do not have hurricanes. John Teal has indicated that the peat-based wetlands are more able to vertically accrete in New England, than the sediment-based wetlands that one finds farther south. And to your credit, three of the five states have adopted policies that at least start to enable wetlands to migrate inland as sea level rises.

Thank you, Jim.

For more on sea-level rise and global warming, check out Jim's site or the EPA’s site.