Rising sea levels, melting glaciers, floods and hurricanes: global warming means urban planners need to rethink how and where to build cities, water experts warned at a conference in Stockholm this week.
Almost 80 percent of the world's population lives less than 50 kilometers (30 miles) from a coastline, a jarring fact given that one of the effects of global warming is rising sea levels, according to the Stockholm International Water Institute (SIWI).
"Thermal expansion of the oceans and melting of glaciers and ice-sheets might endanger low-lying coastal cities if adaptation and mitigation measures are not taken now," SIWI said.
Some 2,500 international experts are gathered in the Swedish capital to discuss water issues, with climate change as the main theme.
"Water management is one important tool to deal with climate change. If you manage water well, you also prepare well for climate change," Kuylenstierna said.
He said the world was facing the double-whammy of a rapidly growing population and global warming.
"For example, Bangladesh a hundred years ago had a quarter of its population today. So if you had floods then the effects were smaller ... Now climate change is added to this," he explained.
Flooding in India, Nepal and Bangladesh since June has affected millions of people and claimed 1,900 lives.
According to SIWI, "climate change combined with continuing population growth and expanding urban centres presents a recipe for disaster."
Kuylenstierna suggested one measure would be to "move people from low-lying areas who live close to the rivers, close to the seas."
"These are attractive areas but maybe we have to finally understand we cannot only work against nature," he added.
He welcomed recent announcements by insurance companies in the United States that they would no longer insure homes if they were built in zones considered to be at risk.
Getting people to change their ways is difficult but "money talks", he said.
According to Sunita Narain, the head of the Centre for Science and Environment in India and a prominent expert at the Stockholm conference, India is in the midst of a major urbanisation process and is experiencing a construction boom in its cities.
She said urban planners needed to take advantage of the possible impact of climate change to reinvent "new models" for clean, sustainable cities.
"Climate change is going to mean more and more uncertain events, more and more floods. There is a need to plan for the water and where it will go," she said, noting that until now urban planning has focused primarily on buildings and not on water.
"We must make our cities more resilient to climate change," she said, stressing the need to implement ways of reducing carbon dioxide emissions to combat global warming, for example in the transport sector.