Demographer Richard Bilsborrow found that population pressures in Latin America contributed to an expansion of cropland area or a reduction in the time fields are allowed to lie fallow. Bilsborrow also saw evidence that populations may respond to the shortage of agricultural land by reducing their fertility, changing technology, or migrating to another area. 48 Water Quality and Scarcity Water, like land, is a renewable resource on which human life depends. Water is one of the most plentiful of the Earth's resources, yet it is unevenly distributed throughout the globe. Vast supplies are frozen in glaciers or stored underground in aquifers that may be tapped only through deep wells.
Waterways often cover wide areas that encompass more than one nation.
Upstream uses can have a significant impact on downstream conditions in another country. In the Ganges River basin, for example, deforestation and water use in Nepal and India have reduced river flows and caused dry-season water shortages, salinization, and depletion of fishery resources in Bangladesh. 49 Much of the increase in agricultural production in recent decades has depended upon large and constant quantities of water. Many less developed countries have made substantial investments in irrigated agriculture, which have boosted yields at a cost to the environment. In some parts of the Indus plains in Pakistan, for example, irrigation led to waterlogging and salinization of the soil.