example, waste disposal and wastewater discharges have been the main causes of soil contamination (UNDP, 2000).
     Soil productivity is closely linked with soil organic mat­ter. In some ESAP areas, long-term experiments have shown declining rice and wheat yields (Nambiar, 1994; Cassman et al., 1995; Brar et al., 1998; Yadav et al., 1998, 2000; Duxbury et al., 2000). The major causes observed were a gradual decline in soil nutrients because of inappropriate fertilizer application, a decline in soil organic matter, atmo­spheric pollution, pest and disease infestation and negative changes in the biochemical and physical composition of soil organic matter (Nambiar, 1994; Yadav et al., 1998, 2000). Observations also have shown that accumulation of nitro­gen in soil was better in farms using organic fertilizer than synthetic fertilizer, possibly from a slow release of nitrogen reducing losses (Bhandari et al., 1992; Yadav et al., 2000). Organic fertilizers are known to stimulate nitrogen fixation in soil and may also be responsible for increasing total soil nitrogen (Roper and Ladha, 1995).

2.4.3.2   Water resource depletion and intensification of water scarcity
Increasing water withdrawal for irrigation has led to serious environmental consequences, particularly water resource depletion and ecosystem degradation. In an area represent­ing 21% of the world's land, ESAP has 28% of its freshwa­ter resources. However, as the region is home to 53% of the world's population, the water resources for each inhabitant are only slightly above half the world's average.
     The hydrology of ESAP is dominated by the monsoon climate, which induces large interseasonal variations in rain­fall and river flow. In the absence of flow regulation, most of the water flows during a short season, when it is usually less needed. In Bangladesh, for example, the surface flow of the driest month represents only 18% of the annual average; in Indonesia, 17%. In India, flow distribution of some rivers during the monsoons is 75 to 95% of the annual flow. In north China, about 70 to 80% of the annual rainfall and runoff is concentrated between May and September (FAO, 2006b). This means that irrigation is important for crops produced the rest of the year. Winter wheat, which accounts for over 90% of total wheat sown areas and production in China, is grown between October and the following June. As there is little rainfall during this period, production is heavily reliant on irrigation, which is the largest water user in the water-stressed North China Plain (Yang and Zehnder, 2001).
     In many rivers in the region, annual discharge declined from increasing water withdrawal. Some rivers have been completely tapped out during the drier part of the year. The Yellow River, the cradle of China's civilization, stopped flowing in its lower reaches for several months every year during the 1990s. The longest dry-up occurred in 1997—a record of 226 days (Postel, 1999). The consequences of re­duced river flows and river dry-ups are serious. The capacity of the river to carry sediment load is reduced, potentially increasing the risk of floods in the lower reach. The dry-ups also adversely affected the aquatic, wetland and estuary eco­systems downstream, in particular the coastal fisheries.
     Overextraction of groundwater and consequent ground-water depletion have been widespread problems, especially

in semiarid areas. In the North China Plain, the ground-water table has declined over one meter each year (Yang and Zehnder, 2001). In Punjab State in India, the situation has been similar. The rapid decline in groundwater tables reduces availability, on the one hand, and increases the cost of accessing the groundwater, on the other. Poorer farmers have been the most affected. When near the sea or in prox­imity to saline groundwater, overpumped aquifers are prone to saline intrusion.
     Water scarcity has become a major concern in many countries in the region. Increased competition for water be­tween sectors has affected agriculture in China, India, the Republic of Korea, Malaysia and Thailand. The problem is intensifying, mainly from population growth and rapid expansion of the domestic and industrial sectors. Major interbasin transfer programs have been reported in many countries, notably China, India and Thailand.

2.4.3.3   Water-quality degradation and nonpoint-source water pollution
Agricultural activities have significantly affected the envi­ronment. Water quality is threatened by intensive applica­tion of fertilizers, herbicides and pesticides that percolate into aquifers. These nonpoint sources of pollution from agriculture have often taken time to become apparent, but their effects can be long lasting, particularly with persistent organic pollutants. Wetlands are also affected by overex­traction of river water and dropping groundwater tables.
     Fertilizer runoff from agricultural production, espe­cially nitrogen, contaminates water supplies. For example, Chinese rice farmers often use inappropriate ammonium bi­carbonate instead of urea and excessive quantities of nitro­gen, 180 kg ha-1 or more, leading to low recovery, 35% or less. In addition to reducing farmer profits, the nitrogen lost from crop and livestock production has contributed "dead zones" being created in the East China Sea at the mouth of the Yangtze River (Li and Daler, 2004). Dead zones can devastate fishing grounds and the livelihoods of those who depend on them for sustenance and income. Improving re­covery efficiencies will require investment in human capital, for both extension agents and farmers.
     In arid and semiarid areas, waterlogging, salinity and alkalinization are serious constraints on agricultural devel­opment in irrigated land. The principal effect of salinity is to reduce the amount of water available to the plant by high osmotic concentration of salts in the soil solution. Saline and alkaline cultivated land in China covers about 7 mil­lion hectares. In India, waterlogging from irrigation covers about 2.46 million hectares. Salination has also been a seri­ous problem in the Murry-Darling Basin in Australia and a number of other countries in the region. Data for areas actually damaged by salination are sporadic and vary widely among sources.
     Animal waste has become a major problem in East Asia and Southeast Asia. With the rapid increases in pig and poultry production in China and Viet Nam, waste run­off from intensive livestock systems has become a major source of nutrient pollution in the South China Sea, one of the most biologically diverse shallow water marine areas. Pig and poultry production has been the primary source of this pollution. Most of this intensive production has been