As world population hits 7 billion, megacities pose growing risks

By Lord Julian Hunt and Professor Yuguo Li
Oct 31, 2011 08:41 EDT The world population has officially reached seven billion, according to the UN. This historic landmark reminds us of the massive challenges, including here in Europe, created by an ever-increasing number of humans on the planet. Growing populations are also driving another mega trend — urbanisation through migration. In 1800, less than 3 percent of the population lived in cities (mainly in Europe), yet by the end of 2008, this had risen to more than 50 percent (much higher still in Europe), and there were 26 megacities (cities of 10 million or more inhabitants), including Moscow, Paris and London. Despite the economic success of megacities, governments at every level are preparing for the growing risks that these massive urban centres pose. For instance, will it be possible to continually meet the everyday needs of food, water, and health, and also deal with the growing vulnerability of megacities to environmental stresses exacerbated by the effects of climate change? There is already cause for some alarm. For instance, the 2003 heat-wave in Paris was so devastating because both the public and authorities were unprepared for dealing with such extreme weather conditions, which were exacerbated by building practices, especially the lack of air-conditioning. Moreover, the tsunami in Japan this year forced Tokyo to re-consider its approach to nuclear power and to protecting its cities. During the 21st Century, megacities in Europe and across the world will continue to grow, as will other large urban conglomerations, such as the Rhine-Ruhr and Po Valley, which have megacity features. Energy demands will thus increase as supplies of food, water, and resources for industries and infrastructure require energy for transportation. The associated increased carbon emissions are contributing to global warming and pose their own climate risks. In China, where people are being subsidised to move from the countryside, cities have grown by a factor of 2 in only 5 years. The local urban ‘heat island’ effect means temperatures are increasing about three times faster than the rate of temperature rise over global and national land areas. The main risk for riverine megacities on coastal plains is their increasing vulnerability to rising sea levels and river flooding, such as those devastating Bangkok right now. There will be further episodes such as the one in New Orleans six years ago when it was hit by Hurricane Katrina, without adequate protection and flood warning systems. In at-risk countries, such as the Netherlands, researchers are preparing for these type of problems. For instance, Delft University’s Hydraulic Engineering Department has been developing a state of the art early warning and monitoring system, including the effects of subsidence, to protect coastal communities. The larger the urban area, the greater the damage that natural hazards can inflict; and increasingly it may be impossible to protect life and property even if there is a perfect warning system. As a recent hurricane in Houston showed, despite the known dangers from combined hazards such as winds and floods, there is now insufficient time to evacuate some cities safely, even highly developed ones. So there is a pressing need for cities to develop emergency refuge areas. In some cases these may already exist. For instance, Canvey Island in England still keeps its mound in case severe floods of the nature of 1953 return. In most cases, however, refuges will need to be built from scratch. Thus, engineers and planners are considering how to identify and design such emergency centres, whether outside or within buildings, and how these should be connected to the wider urban system, including transportation. […]