(Corrects billion to million in para 6)
By Sophie Davies
BARCELONA, Nov 15 (Thomson Reuters Foundation) - Many cities are being overwhelmed by growing numbers of people migrating to them, and will become highly vulnerable to floods, storms and other disasters unless authorities receive more support, urban experts said on Wednesday.
The proportion of the global population living in urban areas has risen from half in 2000 to 55 percent now, and is predicted to reach 70 percent by 2050, according to the U.N. agency for human settlements.
"If we don't start supporting local and national authorities in (the) task of hosting more and more people in their cities, we are going to have cities that are highly vulnerable," said Esteban Leon, chief technical advisor at U.N.-Habitat.
"In most cities ... authorities are overwhelmed by this migration and they don't have the time nor the resources to react," he told the Thomson Reuters Foundation on the sidelines of the Smart City Expo World Congress in Barcelona.
Rapid and unplanned population growth puts pressure on transport, infrastructure and sanitation systems in cities around the world, experts say.
Future urban population growth will not be restricted to megacities of 10 million people or more, said Robert Muggah, co-founder of the Brazil-based think tank Igarapé Institute.
"The vast majority ... is going to be rural folks moving into smaller and medium sized cities ... It's less spectacular but no less significant," Muggah said.
"We're also going to see an incredible amount of growth in the coming decades in informal settlements as a result of the speed of population growth," he added.
About a quarter of the world's urban population live in slums, says U.N.-Habitat.
That amounts to more than 1.2 billion people, which could rise to nearly 2 billion by 2030, Muggah said.
Many of the world's fastest growing cities lack sufficient transport and infrastructure to cope, he said.
"This is putting extraordinary stress on the ability of services to be able to deliver the goods and infrastructure that is so desperately needed by the citizens," he said.
Joan Clos, executive director of U.N.-Habitat, said that urban living is responsible for 70 percent of greenhouse gas emissions.
When a person moves from a rural area to an urban area, their energy consumption increases tenfold, he said.
Problems related to urban population growth must be addressed sooner rather than later, noted Candace Byrd, chief of staff for the U.S. city of Atlanta.
"The time is now to shape the future," she said. (Reporting by Sophie Davies, Editing by Alex Whiting.; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, climate change, resilience, women's rights, trafficking and property rights. Visit http://news.trust.org/climate)
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