ABSTRACT
There is a growing concern that large cities in the Third World will reach a size where the beneficence of nature will be surpassed in terms of providing freshwater, breaking down pollution loads (or through dilution, rendering them less hazardous), providing raw materials and yielding cheap and easily exploitable energy sources. The preceding pages have noted many examples of local ecosystems’ carrying capacities being exceeded: freshwater withdrawals exceeding aquifers’ natural rate of recharge; the level of organic pollutants from industries, sewers and urban run-off exceeding the capacities of rivers and estuaries to break them down; and city-based demands for fuel, timber and bricks exacerbating deforestation, soil erosion and loss of agricultural land. Urban areas often expand over prime agricultural land; so, too, do waste dumps to cope with the increasing volume of solid wastes generated by city-based producers and consumers. In many cities, there are problems of acid rain which damages soils, trees and crops in surrounding areas.
