As more of Asia's population heads for the cities, Singapore can offer clues for planning urban spaces to ensure they remain livable, including by controlling pollution.
"If the city is not well done, immediately you get air pollution. You get traffic congestion and also you spend a lot of time on roads, rather than spending time at home or on recreation," said Dr. Liu Thai-Ker, chairman for the Centre for Liveable Cities and a former head of Singapore's Urban Redevelopment Authority and its Housing Development Board.
"On top of that, the cumulative long-term effect of such a city multiplied by many, many cities obviously will spell the doom for our planet," he said on the sidelines of CNBC's EnergyFuture brainstorming event Tuesday.
Planning for growing urbanization is an urgent topic. A hundred years ago just 2 out of 10 people on Earth lived in cities. Today more than half the world's population lives in cities and that number is expected to rise to around 70 percent by 2050, according to Hot Spots 2025, a report prepared by the Economist Intelligence Unit for Citibank.
In China alone, more than 100 million more people are expected to move to the mainland's cities by 2020, with the country planning to have around 70 percent of its around 1.4 billion population living in urban areas by 2025.
While Singapore is one of the world's most densely populated cities, it's ahead of the curve on green city planning. It has been ranked the most livable city in Asia based on factors including health, safety, demographics and transportation, according to a survey by consultancy PwC.
"In terms of Singapore, we did plan very, very long-term. Because being an island, I feel that we cannot afford to make any mistakes," he said, adding the plan he helped create was meant to stretch out to around 100 years.
But overall, he's not optimistic about the outlook for most Asian cities.
"I see the future of cities as quite worrying because most city officials look at short-term effects," Liu said.
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"A city is a piece of industrial design like a car," Liu said. "If you feel like taking this screw and put it over there, the car will not function. Nobody dares to do that to a car because you see the immediate effect. But people do that to a city (plan) because the effect will not be seen until 30 years later."
To be sure, Lui noted even the best laid plans for cities can go pretty far awry. His master plan was prepared when the city-state's population was around 3 million, with expectations it would rise to 5.5 million by 2091. The current population is already around 5.4 million.
Yet his original plan left a lot of land unused. "If I did not make that long-term plan and allowed the density to be very low, I think today we would be in serious trouble," Liu noted.
Countries across Asia will face similar issues as they plan for higher populations, higher density living and to protect agricultural land, even in places that don't at first appear as land-starved as Singapore, he said.
"China, being a huge country, is equally short of land because a big part of China is a plateau. It's not good farmland," he said, noting cities need to be planned to preserve agriculture. "China is already importing food," he noted.
In addition to planning for traditional issues such as housing, transportation and energy efficiency, cities also must plan for less tangible factors, like livability, he noted.
"I used to live in West End Avenue (in Manhattan) on the second or third floor, facing a light well. And every day, I could get this wide of sunray for half an hour," he said, holding up his hands about 12 inches apart. "We moved to Astoria, which is in Queens, and the first thing I realized is how much my spirit was uplifted by the ability to see the sky, to see the light."
That's why during his 10-year tenure as the head of Singapore's public-housing developer, "I cared a lot about people being able to see the sky, to see the sun."
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter