A view of Karachi, the largest city in Pakistan.Water Aid/Khaula Jamil
Map shows global drying and wetting hotspots.
A new report has revealed how the 100 most populated cities globally are becoming increasingly exposed to flooding and drought.
The study, led by WaterAid with academics from the University of Bristol and Cardiff University, shows widespread drying throughout European cities including the Spanish capital Madrid, which was ranked second among the 49 drying cities, and UK capital London, ranked 44th.
Cities across Africa and Asia are emerging as most at risk to extreme climate shifts, preventing access to clean water and affecting water security for urban communities bearing the brunt of climate change, according to the report.
Findings also indicate almost one in five (17%) of the cities studied are experiencing 'climate whiplash', defined as intensifying floods and droughts. A similar proportion (20%) have seen a major switch from one extreme to the other, known as 'climate hazard flips.'
Co-lead scientist Katerina Michaelides, Professor of Dryland Hydrology at the University of Bristol, said: "The findings from our study illustrate just how differently and dramatically climate change is expressing around the globe – there is no one-size-fits-all."
All European cities analysed exhibit drying trends over the past 42 years, including Madrid, the French capital Paris, and London, which could lead to more frequent and long-lasting droughts.
Of the cities facing 'climate hazard flips', around 13% are switching to a more extreme wet climate, while the remaining 7% are shifting to a more extreme dry climate. This affects more than 250 million people globally in cities including Kano in Nigeria, Bogota in Colombia, and Cairo in Egypt, significantly limiting access to safe and clean water.
Professor Michaelides said: "Places that were historically wet are becoming dry and vice versa. Other places are now increasingly battered by both extreme floods and droughts. A deeper understanding of localised climate hazards can support more intelligent and bespoke planning in major cities."
The study compares each city's social and water infrastructure vulnerabilities alongside new data on climate hazards spanning 40 years to identify which are the most vulnerable to extreme climate changes and the least equipped to handle them.
Vulnerabilities examined range from poverty to poor water and waste systems. Severe urban flooding can damage sanitation facilities, spreading diseases such as cholera and typhoid, whilst water shortages during droughts can leave millions of families without essential water.
Dr Sean Fox, Associate Professor in Global Development at the University of Bristol, who also contributed to the research, said: "as the nature and intensity of natural hazards change, their impacts on urban communities will be significantly shaped by social and infrastructural vulnerabilities. In other words, risk isn't just about the chance of a flood or drought occurring, it's also about how prepared communities are to deal with these hazards."
Hotspots of heightened risk comprised two key regions: south and southeast Asia, and north and east Africa. Cities identified as the most vulnerable include Khartoum, in Sudan, Faisalabad and Lahore in Pakistan, Baghdad in Iraq, and Surabaya in Indonesia, Nairobi in Kenya, and Addis Ababa in Ethiopia.
The report also places European cities like Barcelona, Berlin and Paris at a higher risk than those in North America and Australia, due to the continent's aging water and waste infrastructure, potentially leaving urban populations more exposed.
Co-lead scientist Michael Singer, Professor of Hydrology and Geomorphology, and Deputy Director of the Water Research Institute at Cardiff University, said: "One interesting outcome of this study is how many of the climate hazard trends appear to spread over broad regions, suggesting that there may be significant adaptation challenges to new hazard regimes, but also regional opportunities for collaboration between nations to become more resilient to climate change in urban centres."
From recent drought in cities like Madrid and Cape Town in South Africa, to large-scale flooding across cities in Bangladesh and Pakistan, WaterAid claims 90% of all climate disasters are driven by too much or too little water. It warns that weather-related disasters such as flooding and drought have grown four-fold in the last 50 years, putting major pressure on vital water access and sanitation systems and making it harder for communities and economies to prepare for, recover from, and adapt to climate change.
In light of global aid cuts, Water Aid – the world's leading water, sanitation and hygiene charity – is calling on the UK, global governments, multilateral banks, and the private sector to work together to unlock investment and implement solutions to tackle climate change and water crises, strengthening global security.
Tim Wainwright, WaterAid UK's Chief Executive, said: "We urge the UK to show leadership and maintain its influential role in tackling global climate and health challenges -– essential to creating a secure world free from poverty. Now, we need to turn commitments into action – for leaders to build and invest in systems worldwide that can withstand extreme weather and keep clean water flowing globally."
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