ABSTRACT
Throughout the world fertile land is scarce and subject to a wide range of claims on its use. In view of the growth in world population it is impossible to meet all usage claims to the extent that would be desirable. Instead, careful decisions must be made to give precedence to certain claims and reduce the dominance of others. Human society currently uses around 34 per cent of the world’s land surface for agricultural purposes, primarily for food and feed production (Sections 4.2.2 and 5.2). Added to this is the growing importance of cultivating plant biomass for feedstock uses in products (Section 5.3). The potential availability of agricultural land is restricted by the need to conserve the natural environment, particularly seminatural and natural areas (Section 5.4) and the need to mitigate climate change (Section 5.5). Other limitations arise from overuse – particularly advancing soil degradation – and problems of increasing scarcity and pollution of freshwater resources (Section 5.6). Human-induced changes in natural surface run-off, such as occur when large reservoirs are built, add to the shortage of land suitable for growing crops. The global spread of urbanization and expansion of the associated infrastructure have a similar effect. Cities, urban agglomerations and their infrastructure tend to be concentrated in the most fertile regions of the world (such as river deltas, alluvial fans, riverbank areas and places where rivers divide or converge). This tendency is primarily at the expense of agricultural land. Further expansion of urban structures therefore competes directly with the use of land in the vicinity of settlements for agriculture. Towns, cities and urban agglomerations currently cover – depending on the method of calculation used – between 1.5 per cent and 2 per cent of Earth’s terrestrial surface (calculated from data from Salvatore et al., 2005; Girardet, 1996). Urban structures occupy 4.8 per cent of the land area in Germany (UBA, 2003a) and around 5 per cent in the EU-24 (EEA, 2006). On a global scale, therefore, the direct effects of urbanization in terms of land take are relatively small and so will be ignored here. The following section describes the background to globally competing uses and their future dynamics in the light of the increasing importance of energy crop cultivation.
