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A five-part, multimedia series on the coming dystopia that is urbanization.
80 percent of the garment industry’s 3 million workers in Bangladesh are women.
When describing why they came, migrants tell stories of flood and famine.
Biologist Stewart Brand argues that megacity slums are a boon for planet Earth.
The population of Bangladesh's capital is expected to hit 20 million by 2025.

Dhaka: fastest growing megacity in the world

A five-part, multimedia series on the coming dystopia that is urbanization.

While a third of the newcomers see their incomes fall after arriving in the slums, Islam’s research suggests that over time, the majority hold steady or see their wages rise. “For some people it is a trap,” he said. “But for many people it’s also a platform to move up economically and also socially.”

Some researchers say there are also sound ecological reasons to welcome the dawn of an urban planet. To start with, a planet of cities could avert a scenario where an ever-rising human population is doomed to fight over ever-dwindling resources.

Here’s why: As countries urbanize, birthrates tend to decline. In most industrialized, urban countries, birthrates consistently remain at or below replacement levels, defined as 2.1 children per couple.

The incentives behind the trend are simple, argues Phillip Longman in his 2004 book, “The Empty Cradle.” Rural families need large numbers of children to help raise crops and livestock. But in a city high-rise or crowed slum, there is little or no economic incentive to have children. In fact, for women considering childbearing versus working, the incentives are reversed. The world’s cities are still growing in absolute terms but, as the pool of potential mothers shrinks, population growth will slow and, finally, fall.

“If this seems counterintuitive, think of a train accelerating up a hill,” Longman writes. “If the engine stalls, the train will still move forward for a while, but its loss of momentum implies that it will soon be moving backwards, and at even greater speed.”

Regardless of present birthrates in third-world slums, Longman says the migrants will soon submit to the same pressures that are driving fertility down everywhere else. Urbanization is among the factors the U.N. cites when predicting that Earth’s population will eventually level off around 9 billion.

The trend has led environmental theorists like Stewart Brand to declare that third-world urbanization has “defused the population bomb.”

“The Whole Earth Catalogue” co-founder said the mass shift from rural village to urban slum is good for the planet in other ways, too. Cities — even slum cities — use energy more efficiently than villages do, Brand says, and leaving villages behind helps blunt the environmental devastation wrought by subsistence farming.

“There’s a hell of a lot of landscape growing back. Ecologically that’s great and in terms of climate that’s great,” Brand said.

Rather than fighting informal communities, Brand says governments ought to embrace them, and give slum-dwellers better security, connect them to utility grids and encourage entrepreneurs.

“The old thinking is that slums were the problem,” Brand said. “The new way of thinking is they’re the solution.”