NAIROBI – My mother, like her mother, her grandmother, and so on, was born into poverty in the rural village of Rarieda, Kenya. I, too, was born in the village, and lived there until it was struck by a brutal famine when I was two years old.

With no food, money, or opportunities, my mother did what thousands of African villagers do every day: she moved us to the city in search of a better life. But, given the lack of jobs and housing in Nairobi, we ended up in Kibera, one of Africa’s largest slums.Located just a couple of miles from downtown Nairobi, Kibera is a heavily polluted, densely populated settlement composed of informal roads and shacks with corrugated tin roofs. Kenya’s government does not recognize Kibera, there is no sewage system or formal power grid. Its residents, estimated to number anywhere from a few hundred thousand to more than a million, do not officially exist.Kibera is just one example of the consequences of the rapid urbanization that is gaining momentum worldwide. More than 44% of developing-country residents already live in cities. The Population Reference Bureau estimates that by 2050, only 30% of the global population will remain in rural areas. But few have stopped to consider this shift’s implications for families like mine.When people think of Africa, they often focus on the hardships of village life – a perception reflected in iconic images of African women on their daily excursions to fetch water. But an increasing number of people – already nearly 300 million – are facing the harsh reality of the urban slum, where resources are scarce and economic opportunities are elusive. More than 78% of the urban population in the world’s least-developed countries, and one-third of the global urban population, lives in slums.Nairobi is a dynamic and growing city, with shopping centres, restaurants, and Western-style companies catering to Kenya’s emerging middle class. Yet no one knows how many people live there. According to the last (highly politicized) census, completed in 2009, Nairobi has a population of over three million; but it is probably closer to five million, with a large percentage living in slums.It is these people, Nairobi’s poorest residents, who build the buildings, staff the restaurants, drive the taxis, and power the city. (From the age of 12 until I was 22, I was part of this group, working at construction sites and in factories.) Indeed, without the poor, Nairobi could not function for a single day.Nevertheless, they remain all but invisible, with no political voice. The world’s enduring perception of Africa as a village exacerbates slum dwellers’ plight, keeping them off the global development agenda.Every day, more people arrive in Nairobi, lured by the promise of employment, resources, and a better life, only to realize that they are not equipped to survive there and that their children will grow up in a slum. At least half of those living in urban slums are under the age of 20. Without access to education, this generation – which will soon be the majority – has little hope of ever escaping its straitened conditions.But for how long will a majority serve a minority? For how long will it accept a lack of water, sanitation, education, and dignity?Urban slums worldwide will soon reach a tipping point, with young people rejecting the lives that they have been offered. Their power lies in their numbers – more than half of the world’s youth shares their fate – and in their anger. They will rise up, refusing to accept their status as second-class citizens of ever-expanding urban settlements, and they will destabilize countries like Kenya, undermining efforts to build more stable, prosperous societies.Cities are not just Africa’s future; they are its present. Unless collective action is taken now to transform cities like Nairobi into the drivers of economic development and sources of opportunity that they are supposed to be, they will become a tinderbox of perpetual inequality. For the sake of the millions of people like my mother – and, more important, for the sake of their children and grandchildren – we must fulfill the promise that attracts the poor to cities in the first place.Kennedy Odede is President and CEO of Shining Hope for Communities, a social-service organization in KiberaCopyright: Project Syndicate