A man walks between charcoal burning pits in a squatter community where 300 families subsist by making charcoal.
Slum dwellers in general, Ballesteros said, are prone to poorer health and school performance as well as lower productivity, and they are vulnerable to crimes and violence. They also pay more for basic services such as drinking water. In many cases, there's no electricity, no clean water, and no toilets, and the squatters live in little more than makeshift shelters.
"The people living in slums are highly vulnerable to different forms of risk —both natural and man-made," she said. Such conditions deepen poverty, and make slum dwellers even more vulnerable to disasters and climate change.
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But urban squatters often have nowhere else to go, or resist government resettlement efforts.
"Because of their lack of resources and political clout, the residents of slums often have no choice but to occupy places otherwise unfit for habitation—for example, the rubbish dumps in Manila, the Philippines; flood-prone lands in Dhaka City, Bangladesh, or Mumbai; the polluted shorefronts of Asuncion, Paraguay; or the steep hillside favelas of Rio de Janeiro, Brazil," according to a 2003 UN-Habitat report on slums.
The report said that on average, three-quarters of those living in Manila's slums were long-term residents, meaning they had lived there more than five years.
The Philippines government established a national shelter program for the poor in the 1970s. But until the 1990s, the efforts were largely constrained by cost and the lack of private-sector participation, according to Ballesteros.
Since the 1990s, the government has focused on resettlement efforts and a mortgage financing program that enables urban squatters to purchase lots. There also have been efforts to turn over public areas to qualified groups, Ballesteros said in her report.
The programs have faced a number of challenges, she noted. Resettlement sites are often far from squatters' current jobs, and don't provide enough economic opportunities, especially for women. In some cases, the working member of the family will rent a place in the city, while the family stays in the resettlement area.
Another problem: It is difficult for the the poor to obtain housing assistance, and government support is lacking in providing services to the new communities.
"Over time, some communities have become overcrowded and depressed because the communities are unable to provide for themselves the infrastructure" needed, according to Ballesteros.