The direct causes and symptoms of environmental degradation associated with agriculture abound. With the rapid increase in the use of technologically-enhanced agricultural inputs have multiplied the number of environmental and resource problems. The natural productivity of an estimated one half of the world's cropland is declining because of soil erosion, waterlogging, salinization, and other environmental problems. In certain regions, the misuse of pesticides has led to the development of pesticide-resistant strains of pests, destroyed natural predators, killed local wildlife, and contaminated human water supplies. Improper application of fertilizers has changed the types of vegetation and fish species inhabiting nearby waterways and rivers. The availability of water may become the single most important constraint to increasing yields in the developing countries.
The principal indirect determinants of the environmental impact of agricultural production and processing are many. They include the level of economic development and the extent of poverty; the macroeconomic framework, including monetary/fiscal policies, exchange rate policies, sectoral policies and debt pressure; internation market conditions, including price levels and trade and agricultural policies; the legal framework, in particular property rights; and environmental regulations, not only in the producing country but also in the consuming country in the form of quality requirements and product standards.
Trends documented by the the World Bank and Worldwatch Institute, and reported to the Rio+5 conference in 1997, at that food production has doubled world-wide in the past quarter century, but at the price of loss of crop diversity, natural habitats, and increased chemical contamination. Every major food-producing country is also facing a heavy erosion of its topsoils.