The Indus Civilization (Cambridge History of India, Supplementary Volume) c8.14

c8.14

In summary, it is at least evident that basic climatic change is unlikely to have been the sole or even the main cause in the deterioration of the agricultural conditions of the Indus Valley and its environs. Some reduction in the volume of rainfall within the last 4000 years may indeed be postulated, but there can be little doubt that human neglect or interference was an important contributory factor. Excessive deforestation⁵—possibly effected in part by the Indus brick-makers—inadequate maintenance of such dams and irrigation channels as may have been found necessary, a falling-off in agricultural standards, are all familiar economic and social factors which would result in the reduction of the precipitation of moisture; and, if we add to these domestic potentials the likelihood of ultimate invasion by uncivilized nomads such as the Āryans of the second millennium B.C. and the consequent break-up of organized agriculture altogether, we may safely blame human agency as a major element in the problem. Even the salt-incrustation already referred to is attributable at least in part to human action or inaction: for, if the subsoil-water were absorbed, as it once must have been, by the roots of trees and crops instead of being constantly lifted to the surface by unimpeded solar action, the crust would not be formed to anything like its present deleterious extent.