As towns and cities enlarge, their demands for space and goods increase continuously. To provide land for housing and cities in tropical areas, forests must be removed. In addition to the demand for space, urban areas require great amounts of wood for construction and fuel. The demands of New Delhi for wood, for example, have extended 700 kilometers from the city perimeter. Cities also require many other forest products, from food to roofing materials to medicines. Many of these cannot or are not harvested sustainably, and the excess consumption leads to forest degradation or destruction.