Richard Forman and Jianguo Wu identify several zones around the world that might be suitable for future urbanization (Nature 537, 608–611; 2016). We suggest that the problem of supporting a growing population needs to be considered from a biological as well as an urban-planning perspective: 'suitable' is not necessarily synonymous with 'biologically sustainable'.
The authors propose that urbanization should avoid biodiversity hotspots — regions that are rich in endemic species and undergoing rapid habitat loss. But this would exclude highly biodiverse yet well-conserved areas, which also need environmental protection.
Forman and Wu also call for global-scale planning. Until that is properly coordinated, governments should not view natural ecosystems as offering potential accommodation for the next billion people. Instead, they need to maximize land-use potential while minimizing its biological impact — for example, by improving cities and the surrounding lands that feed them, and by promoting biodiversity research and protection in conserved areas.
We probably do not need more “suitable” land: we need to make sustainable and efficient use of the land we already live on.