The third in a series of stories on Bangladesh and climate migration.

DHAKA, Bangladesh – The towering new orange condominium glistens in the sun, beckoning the city's wealthy to enjoy its luxurious rarities: central air conditioning and a heated pool. In the trash-strewn, sprawling shantytown just below, thousands of the city's poorest live crammed in rows of metal shacks the size of packing crates.

There are sharp contrasts here. The newest-model BMW competes for lane space with ancient wooden rickshas. Stylish teenagers flock to the gleaming mega-mall, watched by shirtless beggars crouched in gutters. The physical space between rich and poor is already narrow. It's going to get even thinner.

Nearly 500,000 people – about the population of Washington, D.C. – move to this city on the banks of the Buriganga River each year, mostly from coastal and rural areas. More than 12 million people live in Dhaka, twice as many as just a decade ago. It's one of the world's most densely populated countries on a planet that is seeing rapid urbanization.

No one knows how many people are being driven to cities by environmental factors exacerbated by climate change, but experts agree that before long we will find out. Global warming will be the dominant factor in moves from rural to urban regions in most developing countries.

"It definitely will play a greater role," said Fatima Shah, a World Bank expert who co-authored a sweeping study last year on climate change impacts on the world's so-called megacities.

"Daily, you hear stories that because of seasonal patterns changing, farmers are not able to sustain the same level of production as in the past," she said.

In Dhaka, migration experts say, climate change already is fueling urban arrivals. Coastal flooding is occurring with more frequency. Rice crops, in particular, are slowly dying because of creeping salinity levels, and in the worst cases, entire homes and villages are lost to fearsome storms.

City growth is most explosive in the slums, where an estimated 3.5 million now live, like 37-year old ricksha driver Omar Faruk.

'I don't have the means to go home'

Standing among the mazes of corrugated metal shacks with no running water or sanitation services, Omar said he left the town of Sherpur, north of Dhaka, "to earn a living." He came from a family of farmers, but when floods ruined the crops in his village last year, he borrowed 500 taka (about $7) to take the bus to Dhaka.

Now he, his wife and their two daughters live in a single room and share a flimsy wooden plank latrine with about 35 other families in the Karail slum, across the river from Dhaka's upper-class Gulshan neighborhood. He isn't likely to go back to Sherpur.

"I don't have the means to go home. I don't have a house or anything over there. It's not possible," he said.

According to the International Organization for Migration, about 70 percent of slum dwellers in Dhaka moved to the city because they experienced some form of environmental hardship.

"This year has been the worst so far because of the flood. The rising water just ruined all the crops," said Mohammad Abdus Salam.

Mohammad, 56, has lived in the Karail slum for nearly 20 years, watching the ebb and flow of migration. In the past, he said, people came to Dhaka, earned some money and returned home. Now, he said, fewer people are leaving.

Just a few months earlier, a storm in Mohammad's hometown of Barisol – a southern Bangladesh town that local scientists say is experiencing higher levels of tidal inundation linked to climate change – devastated the crops.

"Through the years, it's been getting worse and worse, but recently it's gotten very bad," Mohammad said. "This is the time when crops start growing, and these storms just flatten them out. People have come to the city because it's very hard for them to recover from these losses."

A microcosm of rapid urbanization

Abul Hashem, 35, who also came from the Barisol district about seven years ago and drives a ricksha in Dhaka, said he for years went back to his village in crop season. Late last year, though, a storm swallowed his family's house.

"There's nothing to do over there anymore," Abul said. In Dhaka, he shares a room in the Karail slum with his wife and two daughters and works 12 hours a day pedaling a ricksha through the city's cacophonous streets to earn a daily wage of between 150 and 200 taka ($2 and $3). Life is hard here, but Abdul said it's better than the one he left.

"I earn more over here. But even if I had the chance to go back, I wouldn't, because I don't have work," he said.

According to research from the World Bank and other studies, the growth in Dhaka is a microcosm of a rapid urbanization occurring across Asia and Africa. The U.N. Development Programme estimates that 60 percent of the world's population could be living in cities by 2030, and the number of urban slum-dwellers worldwide already has broken the 1 billion mark.

A number of experts worry that fast-growing urban areas will bear the brunt of climate change-related disasters over the coming century, particularly because so many of them, like Dhaka, are located in coastal zones. The World Bank and others say coastal cities could be at greater risk of floods, storms and cyclones. Weather disasters, meanwhile, will be exacerbated by poverty, disease and inadequate housing.

Nancy Kete, a senior fellow at the World Resources Institute, said cities have the potential to be far more resource and energy efficient than rural counterparts, and can even be a haven from climate impacts. But in order for that to happen, she said, "there needs to be planned governance."

More people, more cars, no mass transit and never enough electricity

That's not in evidence in Dhaka, where it's always rush hour and taxi drivers keep both eyes on the road and one hand on the horn at all times. Nearly 15,000 new cars were sold here in 2008, a record high in Bangladesh. But cars share the road with buses, bicycles, rickshas, hand carts, the occasional tractor, and tiny, green compressed-natural-gas taxis. Local experts worry that with no mass transit system nor even adequate pedestrian sidewalks, the traffic system is on the brink of collapse.

Meanwhile, power lines are wrapped like spaghetti over electric poles, and nearly every home and businesses has a backup generator. The government says the country's power generating capacity is at a maximum 4,000 megawatts, which covers only 35 percent of the total population. The newly elected government has vowed to increase power generation to boost economic development.

"We have acute shortages," said Shireen Sayeed, assistant country representative in Dhaka for the U.N. Development Programme. She estimated that by 2015, electricity demand in the city will rise to 10,000 megawatts.

That, she said, creates an enormous opportunity for clean energy projects to promote energy efficiency and renewables at a household level. But she noted that resistance to spending precious dollars on more expensive low-carbon technologies in Bangladesh remains strong. Here, economic growth and fighting poverty remain the top priorities.

"We are one of the most negligible emitters of greenhouse gas," Sayeed noted. But even Bangladesh needs to recognize that its emissions are growing and make a choice. "We can either say, 'We have every right to take on dirty energy; others have done it, and we are a negligible polluter.' Or we can be on moral high ground and also get new, modern technologies that are much better."

Shah said she still has hopes for mega-cities and said leaders need to start viewing land use and other aspects of city planning as critical components of preparing for climate change.

"Properly managed, urbanization can be a good thing," she said. "Improving urban management is itself an adaptation strategy."

Reprinted from Greenwire with permission from Environment & Energy Publishing, LLC., 202-628-6500