Megacities face a growing risk from the planet
ON MONDAY, the world’s population will officially reach 7-billion according to the United Nations. Reaching that historic landmark reminds us of the challenges, including here in Africa, created by an ever-increasing number of humans on the planet.
Growing populations are also driving another trend — urbanisation through migration. In 1800, less than 3% of the world’s population lived in cities, yet by the end of 2008, this had risen to more than 50%, and there were 26 megacities (cities of 10-million or more inhabitants), including Lagos, Cairo and Istanbul.
Despite the economic success of megacities, governments are preparing for the growing risks these urban centres pose. For instance, will it be possible to continually meet the everyday demands for food, water and healthcare, and also deal with the vulnerability of megacities to environmental stresses, made worse by the effects of climate change?
There is already cause for some alarm. The tsunami in Japan this year forced Tokyo to reconsider its approach to nuclear power and to protecting its cities. The 2003 heat wave in Paris was so devastating because the public and authorities were unprepared for dealing with such extreme weather conditions, which were made worse by building practices, especially the lack of air-conditioning.
Megacities across the world will continue to grow, as will other large urban conglomerations. Energy demands will increase. The associated increased carbon emissions are contributing to global warming and pose their own climate risks. In China, where people are subsidised to move from the countryside, cities have grown by a factor of two in only five 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 floodwarning systems.
The larger the urban area, the greater the damage 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, 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. 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, and how these should be connected to the wider urban system.
Because of the failures to deal with some of the recent hazards affecting megacities, governments are planning for multiple hazards and are developing strategies for managing the range of environmental factors that could emerge. Other research teams are collaborating in construction of “system dynamics” models for the operation of infrastructure, environment and the socioeconomic aspects of megacities.
These models resemble well-known computer programmes for global climate change and its interconnections to economic developments. These will help cities to predict which hazards they face and help them decide how to prepare.
What these models need is improved availability of relevant environmental and socioeconomic data. Here, international agencies such as the World Health Organisation and the World Meteorological Organisation, as well as governments, need to collaborate with a wider range of organisations and make maximum use of new media. This will better enable data showing how people experience rapidly occurring hazards such as tornadoes and phenomena such as loss of crops from rising sea levels and salt penetration.
Fortunately, megacities have a global organisation for information exchange and collaboration called C40 Cities.
The agenda includes enhanced intercity co-operation on policies for dealing with hazards and putting more pressure on governments to assist, especially with finance, data and strategic priorities.
Hunt is Vice-chairman of Global Legislators Organisation for a Balanced Environment. Li is Professor of Mechanical Engineering at the University of Hong Kong.