Throwing water on urban growth projections?

The opening ceremonies for the 2016 Rio Olympics were notable for many reasons, including the half mile runway strut of supermodel Gisele Bündchen to the tune of Girl from Ipanema. But for those interested in urbanization, the segment on global warming also drew attention. In the clip viewed by millions around the globe, rising sea levels were shown encroaching across six coastal areas — Amsterdam, Dubai, Florida, Shanghai, Lagos, and Rio de Janeiro. The visualizations were based on a hypothetical four degree Celsius increase in temperature, which could happen by the end of the century if significant policy changes fail to be enacted. Climate Central estimates that 760 million people’s homes (or almost 10% of the world’s population in today’s terms) would be lost in such a scenario.

And, in fact, we are already seeing environmental refugees — the proverbial canaries in the coal mine. Athlete David Katoatau danced at the Olympics weightlifting competition to highlight the environmental plight of his small island state of Kiribati, which has been in the process of resettling its population due to rising seas.

These observations bring me to the subject of urban growth forecasts. Data from the United Nations (UN) World Urbanization Prospects work are widely cited in all sorts of city-focused studies, including the projections that two-thirds of the world’s population will live in cities by 2050 (versus 50% today), and that 90% of that growth will occur in Asia and Africa. The same data is used to say that the number of megacities (those with populations exceeding ten million inhabitants) will grow from 28 today to 41 by 2030. However, as has been noted elsewhere, the methodology used for the UN projections have several shortcomings, including the fact that the projections are comprised of a set of single scenarios for each country and give no sense of the uncertainties inherent to urban transitions. The potential effects of rising sea levels, as well as other climate effects, are one such uncertainty.

Coastal areas have always been highly attractive to humans, for both commercial and aesthetic reasons. Today, roughly two-thirds of the world’s megacities are located in coastal zones. Current studies show that the highest total population exposures to low-elevation coastal zones are in Asia (China, India, Bangladesh, Indonesia, and Vietnam). Africa has significant population exposure in coastal zones including areas in North Africa and along both Sub-Saharan coasts. The U.S. also has a large coastal population, as do Brazil and Argentina. Most of these are areas in which further population growth is expected to take place.

What today’s research doesn’t adequately consider is the potential reversal of coastal population growth due to rising sea levels. The number and scale of projected megacities could be reduced by a combination of out-migration and displacement caused by climate-driven sea levels. It’s feasible to suggest that inland migration could reconfigure the sites and placement of future urbanization. If (or when) the Mekong Delta is inundated by rising sea levels, for example, Vietnam could undergo mass inland migration north to Ho Chi Minh City or the Central Highlands, as well as west into Cambodia. In the U.S., could inland northern states such as Wyoming, North Dakota and Montana receive much more population growth than currently projected?

The 2016 Rio Olympics did a good job at highlighting the impact of rising sea waters on cities, as well as reinforcing the notion that we are one world. Yet even as the closing ceremony was taking place, another alarm bell was sounding by researchers at the University of California at Berkeley. Of all the cities to have ever hosted theSummer Olympic Games, only four will be suitable for acting as host cities by 2085 if aggressive climate change models prove correct. And not a single city in Africa or South America would be viable.

The larger point is this. While population growth is predictable, uncertainty in the form of rising sea levels and other climate effects plague predictions as to the precise future shape of urbanization. Coastal cities have traditionally attracted people with the promise of socioeconomic gains. These cities — with so much to offer — are now on a collision course with climate change-induced forces. This specter should raise the bar for public and private stakeholders around the world to better anticipate and manage coastal areas, as well as to invest resources into creating more intelligent and resilient cities. Making the right policy moves, investments, and other decisions could indeed make today’s urbanization projections prove to be more accurate, but much more importantly, they can ensure that the positive aspects of urbanization for citizens are achieved.

The views reflected in this article are the views of the author and do not necessarily reflect the views of the global EY organization or its member firms.