By 2025, more than half the developing world's population - an estimated 3.5bn people - will be urban. For policy makers and urban planners in poor countries, greener cities could be the key to ensuring safe, nutritious food, sustainable livelihoods and healthier communities.
The concept of "green cities" is usually associated with urban planning in the more developed world. But it has a special application, and significantly different social and economic dimensions, in low-income developing countries.
As cities grow, valuable agricultural land is lost to housing, industry and infrastructure, and production of fresh food is pushed further into rural areas. The cost of transport, packing and refrigeration, the poor state of rural roads, and heavy losses in transit add to the scarcity and cost of fruit and vegetables in urban markets.