As climate change makes itself felt through heatwaves and floods, are our mega-cities ready?

World Population Day is an occasion to reflect on how the world can best address the challenges posed by the combination of urbanisation and climate change

Andrew Hammond

Published: 1:00am, 10 Jul 2021

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As the UK government finalises plans for the forthcoming COP26 climate summit, World Population Day tomorrow will underline how much demographic issues have risen up the political radar in recent years, especially on the sustainability front.

In part, this is driven by the fact that many countries, especially in the developing world, are seeking to redefine what sustainability means with their economic and population growth. This is helping drive the continued rise of the world’s population from around 7.7 billion today, to nearly 10 billion in 2050.

Yet this growth will not be distributed uniformly. According to the United Nations, more than half of it will be concentrated in nine countries, mainly in the developing world, but also including the United States, while in more than 50 countries or areas population is expected to decline, including potentially China.

Overall, growing populations are also driving another mega trend too: urbanisation. In 1800, less than 3 per cent of the population lived in cities, yet by the end of 2008, this had risen to 55 per cent, and there were 33 mega-cities (cities of 10 million or more inhabitants). The percentage of world population living in cities is expected to grow further from 55 per cent to 68 per cent by 2050.

Despite the economic success of mega-cities, governments are preparing for the growing risks that these massive urban centres pose. Key questions to be addressed include whether it will be possible to continually meet the everyday needs of food, water and health, and also deal with the growing vulnerability of large urban areas to environmental stresses exacerbated by the effects of climate change.

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There is already cause for some concern, as shown by the heatwave earlier this month which saw temperatures reaching 20 degrees Celsius higher than normal in parts of the northwestern United States and southwestern Canada. Portland, a typically cool, wet US city, reached 46.6 degrees, which was hot enough to see roads buckling and power cables melting.

This highlights the key issue of preparedness. One reason other heatwaves, such as the one in Paris in 2003, were so devastating is because both the public and authorities were unprepared for dealing with such extreme weather, which was exacerbated by building practices, especially the lack of air-conditioning.

The main risk for riverine mega-cities on coastal plains is their increasing vulnerability to rising sea levels and river flooding. There will be further episodes, such as the one in New Orleans in 2005 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 types of problems. This includes state-of-the-art early warning and monitoring systems, including for the effects of subsidence, to protect coastal communities.

A man stands in floodwater as fire burns down a home in the seventh ward of New Orleans in the aftermath of Hurricane Katrina on September 6, 2005. Photo: Reuters

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 good warning system. As major hurricanes in cities such as Houston have shown, despite the known dangers from combined hazards, such as winds and floods, there is now sometimes insufficient time to evacuate some cities safely, even highly developed ones.

So there is a pressing need for cities to develop emergency refuge areas, which in some cases may already exist, but in most cases 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 transport.

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Training populations to use the centres effectively is also essential. Emergency energy supplies for communities, which are essential for medical emergencies, need to improve in future too, including by using advanced solar power.

Because of the failures to deal with some recent hazards affecting mega-cities, governments are planning for multiple challenges and developing strategies for managing the range of environmental factors which could emerge. Several cities are also experimenting with air quality hazard indicators based on complex system models to apprise citizens of how the environment in their cities varies hourly and over the longer term.

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What these models need is improved availability of relevant environmental and socio-economic data. Here, international agencies such as the World Meteorological Organisation, as well as governments, need to collaborate more and make maximum use of digital technology and communications.

This will better enable data showing how people experience both rapidly occurring hazards, such as tornadoes, and slower – but still deadly – phenomena such as loss of crops from rising sea levels and salt penetration.

Fortunately, mega-cities have a global organisation for information exchange and collaboration called C40 Cities. The future agenda here includes enhanced intercity cooperation on policies for dealing with hazards, and putting more pressure on governments to assist, especially with finance and data, plus strategic priorities.

Andrew Hammond is an associate at LSE IDEAS at the London School of Economics