Water for people.pdf - WHO Thailand Digital Repository

2 1 8 / C H A L L E N G E S T O L I F E A N D W E L L - B E I N GSecuring Food for a Growing World PopulationBy 1997, this had changed to 56 percent, 7 percent and 37 percent.Per capita cereal production nevertheless increased owing to higheryields. Irrigation systems designed for cereal cultivation often do nothave sufficient regulation and the effective water control structuresrequired for crop diversification. Diversification also calls for higherlevels of management capacity, as it is not enough to produce avariety of crops: in addition to being produced, these have to bemarketed. Policy and economic factors such as market incentivesand availability of labour influence the crop choice of farmers.Availability of low-cost pumping technology has supported theexpansion, under private initiative and finance, of diversifiedcropping systems.Agricultural Water Use, Environmentand HealthEnvironmental aspectsAgriculture may have distinct negative externalities in terms of waterquantity and quality. Pasture and crops take up 37 percent of theearth’s land area. Agriculture is the largest water user and the mainsource of nitrate pollution of ground and surface waters, as well asthe principal source of ammonia pollution. It is also a majorcontributor to the phosphate pollution of waterways and of releaseto the atmosphere of the greenhouse gases methane and nitrousoxide. Land degradation, salinization, overabstraction ofgroundwater and the reduction of genetic diversity in crop andlivestock affect the basis of agriculture’s own future. The vanishingAral Sea is a clear example of the irreversible impacts of excessivewithdrawals. The irrigation sector is coming under increasing publicscrutiny as amenity and ecosystem values are lost while theexpected economic and social benefits of irrigation systems are notfully realized. Competition between urban dwellers and agriculture isalso a growing issue and may worsen environmental pressure. Indeveloped countries, environmental concerns have been a key driverfor modernizing irrigation systems.Historically, reclamation of wetlands has made a majorcontribution to agricultural growth. Because of the presence of waterduring a large part of the year and in view of the relative fertility oftheir soils, many wetlands have a good potential for agricultural use.However, this use leads to serious environmental damage, and theimportance of protecting them has been recognized by the adoptionof the Convention on Wetlands (Ramsar, 1971). The developingcountries still have some 300 million hectares of wetlands that maybe suitable for crop production but only a relatively small percentageis currently used to this end. Where no alternative additional landresources are available to exploit, wetlands will inevitably beconverted to crop production. This is the case in many parts of sub-Saharan Africa, where the nutritional situation is bad and wetlandsrepresent an attractive opportunity for agricultural development.However, unwise use of wetlands may result in environmentaldegradation. Draining of wetlands has often been carried out underthe wrong assumption that wetlands are useless and worthless.Sustainable use of wetlands can be achieved by selecting cropsadapted to wetland conditions, using appropriate water and soilmanagement technologies and planning wetland development andmanagement carefully within the framework of the watershed area.Wetlands of particular international or national importance onaccount of their significance in terms of ecology, botany, zoology orbiodiversity should be protected from any agricultural use and fromthe influences of agricultural activities in upstream areas.Water pollution, habitat degradation and massive waterwithdrawals can deprive fishing communities of their livelihood andpush them into food insecurity. The resulting environmental impactsaffecting fishery resources in inland waters can be devastating. Evenin estuarine and coastal zones at the lower end of river basins,fishery resources are impacted by pollution, habitat degradation andupstream water withdrawal and use. It is increasingly recognized thatagriculture also has positive externalities, including environmentalservices and products. The multifunctional nature of agriculture isincreasingly acknowledged and encouraged, so that farmers are seennot only as commodity-producers but also appreciated as selfemployedcitizens, stewards of the landscape and stakeholders invibrant communities. Trade-offs between food security and theenvironment can be further reduced through already available oremerging technologies and land management practices. By usingmore sustainable production methods, the negative impacts ofagriculture on the environment can be attenuated. Agriculture canplay an important role in reversing negative impacts by, for example,environmentally sound water use, biological treatment of waste,enhancing the infiltration of water to reduce flood runoff, preservingagricultural and natural biodiversity, and storing carbon in soils.Water quality deteriorationWith rising demands for water, concerns over water quality haverisen rapidly. Pollutant loads have increased enormously, and at thesame time, the amounts of water available for dilution aredecreasing. The situation is particularly alarming in developingnations while, in developed countries, the enforcement of waterquality measures has resulted in improved conditions for most rivers.Deterioration of water quality poses a serious threat to thesustainability and the safety of food produced by intensive farmingsystems upon which global food security has become increasinglydependent. Security and stability in food supplies in this century willbe closely linked to success in water quality control. Organic matter,if free of pathogens, can actually be beneficial to irrigated