The long-term consequences of human activities on the natural resource base. The most important ways in which human activity is interfering with the global ecosystem are: a) fossil fuel burning which may double the atmospheric carbon dioxide concentration by the middle of the next century, as well as further increasing the emissions of sulphur and nitrogen very significantly; b) expanding agriculture and forestry and the associated use of fertilizers (nitrogen and phosphorous) are significantly altering the natural circulation of these nutrients; c) increased exploitation of the freshwater system both for irrigation in agriculture and industry and for waste disposal.