RIO DE JANEIRO, Brazil — High on a hillside west of Rio, workers in the Tijuacu favela smooth mortar on bricks near shiny sewage treatment tanks, and carry bags of concrete on their shoulders to a new gravity-fed water system at the edge of the forest. Soccer fields punctuate the base of the steep slope, cluttered with makeshift homes.

A couple hundred miles away, at an undeveloped subdivision in Sao Paulo occupied by 56,000 people, residents have been relocated from the muddy banks of a stream to make way for proper drainage and a ribbon park; the area, called Paraisopolis, also got a music school and outdoor cinema.

And then there are the slums in Medellin, Colombia's second largest city, that now have access to cable trams, playgrounds and libraries so well-designed the young people living there had to be assured that the facilities were indeed for them.

In the face of a dizzying global crisis — an estimated 1 billion people living in informal settlements, shantytowns, slums and favelas make up about 30 percent of the global urban population — planners and politicians have found success with more incremental steps toward improving conditions for the urban poor.

Instead of mass evictions and bulldozing, local governments are working with vast, illegally occupied settlements where they are trying to make life a little better with basic services such as electricity, water, sewer and sanitation systems, as well as what some are calling “socio-ecologic” infrastructure.

The problem of slums has been worsening in recent years, as millions from rural areas flood into burgeoning mega-cities that lack the economic, housing and infrastructural capacity to accommodate them.

The place “where the pavement ends,” as many of these areas are known, have been besieged by high child mortality, disease and, of course, crime. The subject was central at the UN-Habitat’s World Urban Forum 5, held last week in Rio de Janeiro, where organizers wrestled with how to provide basic services for the most urban poor.

A form of urban renewal — bulldozing shantytowns and in the best cases, relocating residents in public housing — was a popular solution dating at least back to the 1970s. But then slum removal became politically untenable, and a new way of thinking about informal settlement emerged, shared by Jane Jacobs and others: That the places “where the pavement ends,” as many slums are known, were organic, ingenious and resourceful urban systems that should somehow be respected and built upon.

That is the philosophy behind high-profile programs such as Favela-Bairro, with targeted investments in infrastructure, services, open space and community facilities, as well as relocations from the most risky areas, such as floodplains or mudslide-prone sites.

The idea is to consolidate, establish a boundary to protect bordering environmental resources, and while falling short of giving squatters title to their land, bring them closer to being part of the formal city — even with something as simple as an address or concrete stairs.

“It makes a big difference in quality of life. It tells them they will not be evicted,” said Rio architect Adrianna Larangeira, who has worked in housing and for Favela-Bairro.

An additional feature addresses sustainability — painting rooftops white, or using natural systems to cleanse polluted waterways, such as growing hyacinth in one slum in Nairobi; the typically invasive plant is harvested and dried for making crafts. Planners even use the term “communities” these days to refer to favelas.

Yet the process, generally known as “regularization,” is by no means a panacea. Many favelas are rocked by drug-related violence first and foremost. Upgrading initiatives are highly targeted, and a drop in the bucket given the massive numbers of slum dwellers; some have been labeled publicity stunts that reward local politicians unwilling to tackle the more ambitious provision of new public housing.

The U.N. has estimated that the costs of upgrading can be $7,000 per family — far too expensive on its face, let alone for large-scale interventions.

In addition, the improvements can send the signal to newcomers that they should occupy new areas of the city, however inappropriate for human settlement — with the expectation that they will be regularized in time.

Upgrading can only work if coupled with the prevention of new favelas, and that means the construction of more public or “social” housing or, better yet, the provision of serviced lots. There is, of course, less of an appetite for those kinds of projects, especially when it comes to paying for them.

If major cities are serious about acting on slums — and Rio, preparing for the World Cup and the Olympics, surely falls into this category — ultimately they must rethink how to finance infrastructure and housing for the poor, possibly with new systems such as a land value tax in more privileged areas of the city.

In the meantime, though, there is no denying the impact of improvements, even if it improves the lives of only a handful of children at a time. As Martim Smolka, who has been doing training for years on regularization as part of the Lincoln Institute’s Latin America program, has noted, the only action that is not an option is to do nothing.

Anthony Flint is a Boston-based writer at the Lincoln Institute of Land Policy, and author of "Wrestling with Moses: How Jane Jacobs Took On New York's Master Builder and Transformed the American City" (Random House).

Editor's note: This story has been updated to reflect the name of the Tijuacu favela.

Related Stories