The physical impacts of climate change on coastlines are bad, but the human impacts could be even worse. The reason is that humans put more pressures on coasts than any other area. Using a definition of the coastal zone as those areas within 100 km (62 miles) of the coastline and with an elevation below 100 m (328 feet), then 23 percent of the global population lives in the coastal zone. There are 24 coastal cities with populations in excess of 5 million people, and there are 10 cities with more than 10 million people, including such major metropolitan areas as Los Angeles, New York, Sao Paolo, London, Mumbai, Shanghai, and Tokyo. Sea level rise, therefore, puts enormous populations at risk. It also puts many trillions of dollars of the built environment at risk, including entire settlements. Experts agree that the impacts of billions of people are greater than the impacts of climate change on the coastal zone, but that climate change is making things worse.
To understand the human risks of climate change in the coastal zone, it is useful to examine the vulnerability of coastal people and places to climate change impacts. Recall that there are three dimensions of vulnerability: exposure, sensitivity, and adaptive capacity. Exposure usually relates to physical vulnerability, whereas sensitivity and adaptive capacity relate to social vulnerability.
As described in the account of physical impacts above, exposure of coastal people and places is increasing. Climate change is exposing billions of people and their built environment to rising sea levels, more intense storms, enhanced storm surge, and worse coastal erosion. These people are exposed to degrading and reduced ecosystems, upon which many people depend for their livelihoods.
How much this increased exposure harms people and places depends on their sensitivity. In underdeveloped and developing countries, hundreds of millions of people residing in the coastal zone live in poverty, and their meager livelihoods are at risk of harm by climate change. Many of these people are very young or very old, which makes them even more sensitive. In addition, these impoverished people tend to live in substandard housing, without running water or adequate sanitation, nutrition, and health care; burgeoning poverty, corruption, and overcrowding mean that many of these areas are getting worse, rather than better over time. Coastal hazards associated with climate change exacerbate these infrastructural challenges, sometimes greatly.
Impacts on Coastal Environs in Developing Countries
In developed societies, socioeconomic safety nets are much greater and far fewer people are directly sensitive to the impacts of climate change. Instead, the sensitivities relate to the built environment and can still be great. Inundation from sea level rise and storm surge are the greatest threats. Consider the case of New York City, where trillions of dollars in sophisticated infrastructure -- subways, telecommunications, sewers, and water systems -- exist below ground and could easily be submerged by storm surge in the short run and permanent inundation in the long run. If such flooding occurred, the impacts would cascade around the world. For instance, if workers in the financial district could not get to work because the subways were closed, and if the telecommunications connecting to the New York Stock Exchange were to go down, financial chaos and crisis would spread worldwide. Given that the world’s three major financial centers (New York, London, and Tokyo) are coastal cities, it is clear that in the long term even rich societies are sensitive to coastal zone impacts of climate change.
In sum, it is possible to say that sensitivity to climate change is increasing in the coastal zones of undeveloped, developing, and developed countries. In poorer societies, sensitivities tend to involve direct impacts on people, but in richer societies, sensitivities are to infrastructure and therefore are felt by individuals and households indirectly. The interconnectedness of the global society means that coastal zone sensitivities and impacts propagate throughout the world. This sensitivity to climate change is mounting, sometimes dramatically, in all coastal areas because of the ever-growing populations and their infrastructure.
Adaptive capacity provides the means to decrease vulnerability by either reducing exposure or lessening sensitivity. In the coastal zone, adaptive capacity varies greatly at all scales, from person to person, household to household, neighborhood to neighborhood, settlement to settlement, and country to country. Many factors affect adaptive capacity -- financial resources, technological resources, political resources, and many more. All things being equal, people and places with greater financial resources have greater adaptive capacity. For instance, a rich city might be able to afford to build a sea wall around the city, but a poorer city might not. The rich city is more likely to have a strong intellectual and educational heritage and the technological means to design the sea wall, whereas the poorer city might still possess these characteristics, but it cannot apply them without access to funding. However, even the rich city might not be able to build the sea wall if the political elite are ideologically opposed to doing so; if the poorer city does not follow that ideology and has strong political connections to the nation’s rulers and access to national funds, then they might, in the end, be able to build the sea wall.
From coasts to cities
Now that we've spent some time understanding the ways in which climate change will affect our coastal environment, let's take a closer look at the vulnerabilities of our cities.