The urgent need to reconfigure and transform urban areas to consume fewer resources, emit less pollution, minimize greenhouse gas production, protect natural ecosystems and increase the adaptive capacity to deal with climate risks is widely recognized.

The city of Dar es Salaam, with a population of more than four million, has no climate change adaptation plan. It also has a very large development deficit and lacks adequate provision for infrastructure and services such as piped water, sewers, drains and solid waste collection. Addressing this deficit (and building the institutional and financial capacity to do so) is also important for building resilience to climate change impacts.

Many villages gradually get included in cities and urban people also migrate to villages transforming them into towns. Both phenomena require intensive study, including an examination of the defi ning criteria of a "town", and the estimates of urban population.

Urban land-cover change threatens biodiversity and affects ecosystem productivity through loss of habitat, biomass, and carbon storage. However, despite projections that world urban populations will increase to nearly 5 billion by 2030, little is known about future locations, magnitudes, and rates of urban expansion. Here we develop spatially explicit probabilistic forecasts of global urban land-cover change and explore the direct impacts on biodiversity hotspots and tropical carbon biomass.