downstream communities, national citizens and the global population. These issues of scale are seldom incorporated into ROR calculations or other decision-making tools, and thus they exclude the critical elements of "who pays, who benefits". Second, reconciling different levels of aggrega­tion to obtain reliable estimates is complex. For example, movement of pesticides through soil is determined by sev­eral factors such as specific soil characteristics (physical and chemical), properties of the soil, the climate, crop manage­ment practices, and so on. The problem is how to generate information that reflects the complex of physical, biological and technical factors. One of the more difficult areas to esti­mate is the value of impacts on and by biodiversity, because the links between biodiversity and ecosystem functions and services is less understood than many other environmental interactions. Moreover, no monetary values can be given to it and the value is also context-specific and relative to the livelihoods and uses given to biodiversity. The willingness is related to the knowledge of the impacts of biodiversity loss, including the impact of climate change (Turpie, 2003).
        New development in economic science, such as eco­logical economics, can bring promising tools in the future to measure externalities and tackle the problems identified above (Proops, 1989; Jacobs, 1996). One example is the evaluation of one century of agricultural production in the Rolling Pampas of Argentina by analysing energy flows within systems (Ferreyra, 2006). The ecological footprint quantifies the amount of resources required by a produc­tion method or a technology related to AKST, and thus can give an idea of the environmental impact (Wackernagel and Rees, 1997) and was used to assess the resource use and development limitations in shrimp and tilapia aquaculture (Kautskyetal., 1997).
          Due to the complexity of agriculture and the links with the food chain, most studies, particularly ecological eco­nomic studies, examine the impacts of food systems and not the technologies in isolation. There is a significant paucity of data and studies on environmental impacts (see below as well as Table 8-14).

8.2.5.1 Agriculture
Biodiversity loss. Reduction in the use of biodiversity in ag­riculture is driven by the increased pressures and demands of urban and rural populations and by the global develop­ment paradigm, which favors specialization and intensifica­tion (FAO, 2003). Most studies combine influences and im­pacts from crop and livestock systems. The total economic benefits of biodiversity with special attention to the services that soil biota activities provide worldwide is estimated to be US$1,542 billion per year (Pimentel et al., 1997). The es­timated total damage to UK's wildlife, habitats, hedgerows and drystone walls was £125 million in 1996 (Pretty et al., 2000).

Soil erosion. Scientists estimate the global cost of soil ero­sion at more than US$400 billion per year. This includes the cost to farmers as well as indirect damage to waterways, infrastructure, and health (Pimentel et al., 1995). In the UK, the combined cost of soil erosion with organic carbon losses was £106 million in 1996 (Pretty et al., 2000).

Pesticides and chemical fertilizers. Agricultural runoff pol­lutes ground and surface waters with large amounts of ni­trogen and phosphorus from fertilizers, pesticides and agri­cultural waste. Agriculture is the main cause of pollution in US rivers and contributes to 70% of all water quality prob­lems identified in rivers and streams (Walker et al., 2005). In the UK the cost of contamination of drinking water with pesticides is £120 million per year (Pretty et al., 2000).

Carbon sink. Agricultural systems contribute to CO2 emis­sions through several mechanisms: (1) the direct use of fos­sil fuels in farm operations; (2) indirect use of fossil fuels through inputs, such as fertilizers; and (3) the loss of soil organic matter. On the other hand, agricultural systems ac­cumulate carbon when organic matter is accumulated in the soil, or when above-ground woody biomass acts either as a permanent sink or is used as an energy source that sub­stitutes for fossil fuels (Pretty and Ball, 2001). A 23-year ongoing research project by the Rodale Institute in the US found that if 10,000 medium-sized farms in the US con­verted to organic production, the carbon stored in the soil would equal taking 1.2 million cars off the road, or reduc­ing car travel by 27 billion kilometers (The Rodale Insti­tute, 2003). Forty sustainable agriculture and renewable-resource-management projects in China and India (Pretty et al., 2002) increased carbon sinks in soil organic matter and above-ground biomass; avoided carbon emissions from farms by reducing direct and indirect energy use; and in­creased renewable energy production from biomass. The potential income from carbon mitigation is $324 million at $5 tonne-1 of carbon (Pretty et al., 2002).

Water use. Agriculture consumes about 70% of fresh water worldwide. For example, the water required for food and forage crops growing ranges from about 300 to 2,000 li­ter kg-1 dry crop yield, and for beef production 43,000 liter kg-1 (Pimentel et al., 2004). Virtual water refers to the water used in the production process of an agricultural product (Chapagain and Hoekstra, 2003). Using a virtual water ap­proach, some countries are net importers of water while others are exporters. It is expected that in the future, ap­proaches to quantify the amount of water used by different countries or regions will be extremely important.

8.2.5.2 Livestock The livestock sector has enormous impacts on the environ­ment: it is responsible for 18% of GHG emissions measured in CO2 equivalents, and 9% of anthropogenic CO2 emis­sions, including the combustion of fossil fuels to make the additional inputs. Globally, it accounts for about 8% of human water use, mostly for the irrigation of feed crops (Steinfeld et al., 2006). It is estimated that 1 kg of edible beef results in an overall requirement of 20 to 43 tonnes wa­ter per kg of meat (Smil, 2002; Pimentel et al., 2004). The total area occupied by grazing is equivalent to 26% of the world land; the total agricultural area dedicated to feedcrop production is 33%. In all, livestock production accounts for 70% of agricultural land and 30% of land globally (Stein­feld et al., 2006). It is probably the largest sectoral source of water pollution. In the US, livestock are responsible for