habitats and biodiversity (FAO, 2006d). Additionally, livestock require regular access to water resources, which they deplete and contaminate. On the other hand, extensive pastoral systems like game ranching, are more compatible with biodiversity conservation than most other forms of agriculture (Homewood and Brockington, 1999).

Intensive agricultural systems can damage agroecosystem health.

Agroecosystem health is important for nutrient, water and carbon cycling, climate regulation, pollination, pest and disease control and for the maintenance of biodiversity (Altieri, 1994; Gliessman, 1998; Collins and Qualset, 1999). Intensive production systems, such as the rice-wheat system in the Punjab, have led to deterioration in agroecosystem health, as measured by soil and water quality (Ali and Byerlee, 2002). This deterioration has been attributed to unsustainable use of fertilizer and irrigation, though whether this is due to intensification per se or to mismanagement is unclear. For example, in China, grain yield would have increased by 5% during 1976-89 given less erosion and less soil degradation (e.g., increased salinity) (Huang and Rozelle, 1995). More evidence is needed about the relationships between total factor productivity and long-term agroecosystem health. In some cases, intensified production on prime agricultural land may reduce negative impacts on ecosystem health by reducing the incentive to extend production onto marginal lands or into natural areas (e.g., highly erodible hillslopes).

Poor irrigation management causes land degradation with negative impact on livelihoods.

Irrigation increases crop productivity in dry areas, but can result in land degradation. Poor drainage and irrigation practices have led to waterlogging and salinization of roughly 20% of the world's irrigated lands, with consequent losses in productivity (Wood et al., 2000). While livelihoods have improved through increased production and employment, demands for irrigation water have degraded wetland biodiversity (Huber-Lee and Kemp-Benedict, 2003 quoted in Jinendradasa, 2003). Poorly conceived and implemented water management interventions have incurred high environmental and social costs, including inequity in benefit allocation and loss of livelihood opportunities. Common property resources such as rivers and wetlands, important for poor fishers and resource gatherers, have been appropriated for other uses, resulting in a loss of livelihood opportunities. Communities have been displaced, especially in areas behind dams, without adequate compensation. A large proportion of irrigation's negative environmental effects arise from the diversion of water away from natural aquatic ecosystems (rivers, lakes, oases, and other groundwater dependent wetlands). Direct and indirect negative impacts have been well documented, including salinization, channel erosion, declines in biodiversity, introduction of invasive

alien species, reduction of water quality, genetic isolation through habitat fragmentation, and reduced production of floodplain and other inland and coastal fisheries.

In some river basins, water scarcity due to irrigation has become a key constraint to food production.

Fifty years ago water withdrawal from rivers was one third of what it is today, with 70% of freshwater withdrawals (2,700 km3 or 2.45% of rainfall) attributable to irrigated agriculture (CA, 2007). About 1.6 billion people live in water-scarce basins. Water availability is a worldwide problem (Figure 3-4) despite a decline in water withdrawal for agriculture over the past 20 years (FAO AQUASTAT, 2007) in developed (58 to 39%) and developing countries (76 to 71%), a decline of 69 to 61% globally (FAOSTAT, 2006). In both irrigated and rainfed areas, a decline in water available for irrigation, without compensating investments and improvements in water management and water use efficiency, has been found to reduce production with a consequent increase in international cereal prices and negative impacts on low-income developing countries (Rosegrant and Cai, 2001). Global investment in water distribution systems for agriculture has declined relative to other sectors during recent decades.

Agriculture contributes to degradation and pollution of water resources.

Traces of the herbicide "Atrazine" and other pesticides are routinely documented in shallow ground and surface waters in industrialized countries. Recent surveys in the U.S. suggest that pesticides concentrations exceed human health and wildlife safety standards in approximately 10% of streams and 1% of groundwater wells (USGS, 2006). In intensive agricultural regions, streamwater nitrogen concentrations have been found to be nearly nine times higher than downstream from forested areas (Omernik, 1977). Increasing concentrations of nitrate nitrogen in the Mississippi River have also been linked to hypoxic conditions in the Gulf of Mexico (Rabalais et al., 1996).

3.2.1.1.3 Impacts on diet and health

Patterns of food consumption are becoming more similar throughout the world,

The Green Revolution did not focus on nutrient-rich foods like fruits, vegetables, legumes and seafood. The focus on cereals led to an increased per capita consumption of cereals, while in most developing countries, consumption of vegetables remained far below the minimum requirement level of 73 kg per person (Ali and Abedullah, 2002). Likewise, per capita consumption of pulses in south Asia fell