The present-day vegetation in South Asia is the product of millennia of human activity and exploitation. Trees have been felled for timber, for use in constructing buildings and ships, for making furniture, tools, and other artifacts, or for fuel for domestic and industrial purposes. Forests have been cleared to open up land for settlement and cultivation. Modern tree cover is therefore far less dense and far less widespread than in ancient times, and the moist deciduous forests of trees growing up to 120 feet tall that once covered most of the greater Indus region have widely been replaced by dry deciduous forest, with shorter trees, and by scrubby thorn forest, associated with poorer soil fertility, lower water retention, reduced plant cover and diversity, and greatly reduced fauna. Forest regeneration has been inhibited by grazing herds of domestic animals, which have also had a marked effect on other vegetation. Firing the enormous quantity of baked bricks used in constructing Indus cities could have decreased the extent of vegetation cover, although studies have shown that even the present-day scrubby vegetation of the region could have provided a sustainable source of fuel adequate for the purpose. Manufacturing charcoal for the fuel used in smelting copper may have had a more significant impact: During the Harappan period at Lothal, charcoal was made from a variety of trees from the local deciduous forests, but by the latest Harappan levels it was being made only from scrubby acacia, and animal dung was also in use as fuel, suggesting that tree felling had significantly affected the local forest cover by this time.
Deforestation and overgrazing over the millennia have caused considerable erosion, increasing runoff and hence increasing the volume and speed of water in the Indus, in turn increasing the risk of excessive and devastating floods. These activities have also brought about environmental degradation and a reduction in moisture retention by soils and plants, as well as the reduction or local extinction of much of the native fauna. This process may have begun by the Indus period: Evidence of environmental strain by the second millennium BCE has been found in some areas such as the Kachi plain. Nevertheless the severe degradation of much of the flora and fauna of the subcontinent is by and large a more recent development.
In ancient Mesopotamia and in parts of South Asia in historical and recent times, regular irrigation over a prolonged period caused salinization, eventually turning land into a salt waste where cultivation became increasingly
A view of Mohenjo-daro through the morning mist. The modern environment of the Indus Valley bears little resemblance to that in Harappan times. Agriculture, animal grazing, and forest clearance have taken their toll on the once-lush natural vegetation and abundant, diverse fauna. The river has repeatedly changed its course and canals and dams have been added. (J. M. Kenoyer, Courtesy Department of Archaeology and Museums, Government of Pakistan)
Difficult and eventually impossible. Although this cycle would also have taken place in the ancient Indus Valley if artificial irrigation had been employed, there is no evidence from the Indus period either of large-scale irrigation or of salinization there: The annual river floods and limited rainfall seem to have been adequate to support agriculture in the plains.
World History
