POPULATION MOMENTUM AND THE DEMAND ON LAND AND WATER-RESOURCES

Future world population growth is fuelled by two components: the demog raphic momentum, which is built into the age composition of current po pulations, and changes in reproductive behaviour and mortality of gene rations yet to come. This paper investigates, by major world regions a nd countries, what we know about population growth, what can be projec ted with reasonable certainty, and what is pure speculation. The expos ition sets a frame for analysing demographic driving forces that are e xpected to increase human demand and pressures on land and water resou rces. These have been contrasted with current resource assessments of regional availability and use of land, in particular with estimates of remaining land with cultivation potential. In establishing a balance between availability of land resources and projected needs, the paper distinguishes regions with limited land and water resources and high p opulation pressure from areas with abundant resources and low or moder ate demographic demand. Overall, it is estimated that two-thirds of th e remaining balance of land with rainfed cultivation potential is curr ently covered by various forest ecosystems and wetlands. The respectiv e percentages by region vary between 23 % in Southern Africa to 89 % i n South-Eastern Asia. For Latin America and Asia the estimated share o f the balance of land with cultivation potential under forest and wetl and ecosystems is about 70 percent, in Africa this is about 60 %. If t hese were to be preserved, the remaining balance of land with some pot ential for rainfed crop cultivation would amount to some 550 million h ectares. The regions which will experience the largest difficulties in meeting future demand for land resources and water, or alternatively have to cope with much increased dependency on external supplies, incl ude foremost Western Asia, South-Central Asia, and Northern Africa. A large stress on resources is to be expected also in many countries of Eastern, Western and Southern Africa.