Are urban areas endangering the availability of rainfed crop suitable land?

Many concerns have been raised about urban sprawl and the subsequent disappearance of agricultural land. Regulations have been put in place to reduce urban sprawl and protect agricultural areas in many countries, but how much potentially crop suitable land really is endangered by urban areas on a global scale has not been addressed so far. In this study, we compare the extent of urban areas as produced by the Center for Sustainability and the Global Environment, Madison, WI, USA, with a map of potential crop suitable areas produced by us. We show that, of the postulated 0.5% of the Earth's surface currently covered by urban areas, Asia, Europe and North America take away the largest shares and that 1% of the globally available highly crop suitable areas are currently taken up by cities, with Japan and California being extreme examples of up to 15% of highly suitable areas covered with cities.