Rapidly rising sea level and the future of our coasts

Humans have been adapting to changes in the environment for thousands of years. Probably since the beginning of time, we have roamed the Earth looking for the best place to settle based on our needs as farmers, herders, hunters or fishers. Today, however, we face a challenge that is unprecedented in human history. Our fixed infrastructure, particularly our cities, are too large, too populous and too expensive to move in the face of accelerating sea-level rise.

As a result, we need to come up with new ways to address the changes we see going on around us, including those forecasted in the short- and long-term. 

A new mapping tool by Climate Central presents the potential impacts due to flooding from projected sea-level rise on coastal communities around the world. The results are useful for planning, but even before it was released Boston and New York City had already taken actions to plan and mitigate sea-level rise impacts, and Florida recently appointed its first Chief Resilience Officer. Other coastal communities, large and small, would do well to follow those examples and consider the future presented in the Climate Central analysis.

There are a few undeniable truths about our current situation that underscore the need to act. First, sea level is rising, and it is rising at an accelerating pace in many locations. We can see this in the observational record provided by tide gauges up and down our coasts, as well as in the projections generated by any number of computer models. Second, the exact amount and rate of rise is both difficult to predict and highly variable depending on any number of local and regional factors. 

These simple truths are clouded by the fact that interactions between humans and nature in the coastal zone are, and will continue to be extremely complex. This is particularly true with respect to natural disasters, which need to be seen as the joint product of environmental and human processes at work. Damage caused by coastal storms, for example, are affected by the frequency and magnitude of storm events, which are themselves influenced by human activity, as well as human management decisions and the socio-economic conditions of coastal communities. 

Because of this, there are likely to be no perfect or permanent solutions — a harbor storm-surge barrier could be functional for a few decades up to a designed sea level limit before it needs to be rebuilt, moved, or abandoned. Instead, we should view sea-level rise adaptation from the context of sustainable hazard mitigation, which holds that sustained actions, before, during and after disasters, should be taken to reduce or eliminate the long-term risk to life and property from hazards. These actions should consider longstanding, social-environmental effects, rather than addressing individual problems in isolation.

In the near term —  less than 30 years — plans and actions are needed that will improve the resilience of coastal communities. These include gray (seawalls) and green (living shoreline) coastal protection, preservation of coastal wetlands and mangroves that provide natural defenses, improvements in social capital, disaster training and education, land use planning, enforcement of building codes and diversification of economies, to name just a few of the options. 

Each community should evaluate the environmental resources available and the potential hazards it faces, choose future losses that it is willing to bear, and then take steps to ensure that development and other community actions and policies adhere to their plan.

Over the long term, disaster management and planning require that we take into account the overall effect of mitigation efforts on current and future generations. In this context, managed retreat is likely to be the only course of action available in many places. In the meantime, communities will have to take responsibility for decisions about where and how development proceeds through land use planning and with an eye towards a future that many of us will likely never see. 

Finally, any action we take to address either short- or long-term goals, will greatly benefit from, if not require, input from the scientific research community to ensure that we are making the best investments possible for the most effective coastal protection systems available.

Dr. Di Jin is a senior scientist at the Marine Policy Center of the Woods Hole Oceanographic Institution, where he specializes in the economics of marine resources management and marine industries.