forage for livestock, wildlife habitat, and a host of other resources (White et al., 2000).

     Grasslands provide feed for livestock farming across the globe as well as a wide range of ecosystem services. For instance, grasslands provide part of the cover to some of the world's major watersheds. Most of the world's meat comes from animals that forage on grasslands. World meat production has doubled since 1975, from 116 million to 233 million tonnes in 2000 (UNEP, 2002). Grasslands are also a major component of important areas of bird endemism and wildlife sanctuaries, and store approximately 34% of the global stock of carbon in terrestrial ecosystems.

     Nearly 49% of grasslands are lightly to moderately degraded and at least 5% are considered strongly to extremely degraded (White et al., 2000). The degree of degradation is dependent on geographical location and management practices as well as on characteristics of the soil, vegetation, and grazing patterns. Cultivation and urbanization of grasslands, and other modifications can be a significant source of carbon to the atmosphere. For instance, biomass burning, especially on tropical savannas, contributes over 40% of gross global carbon dioxide emissions (Baumert et al., 2005).

Fisheries

Fish play a key role as an economic commodity of significance to a great number of farming households and rural poor people. Inland fisheries and aquaculture-for example in irrigated rice agroecosystems-are not only important as a direct food source: fish are also a high value commodity that can be traded for cash, for other needs and cheaper foods, by small-scale farmers and the poor, and provide a source of direct employment for 38 million and indirect employment for about 160 million people (FAO, 2004b; ICTSD, 2006). The highest share of fish workers (fishers and aquaculture workers) is in Asia (87%), followed by Africa (7%), Europe, North and Central America and South America (about 2% each) and Oceania (0.2%) (FAO, 2004b).

     In 2002, about 76% (100.7 million tonnes) of estimated world fisheries production was used for direct human consumption. The remaining 24% (32.2 million tonnes) was destined for non-food products, mainly the manufacture of fishmeal and oil, slightly (0.4%) above levels in 1999 but 5.8% below levels in 2000 (FAO, 2004b). In 2002, total capture fisheries production amounted to 93.2 million tonnes. Marine capture fisheries production contributed 84.5 million tonnes. Between 2000 and 2003, the reported landings of marine capture fisheries have fluctuated between 80 and 86 million tonnes: a slight increase over the preceding decade (mean = 77 million tonnes). Production from different capture and culture systems varies greatly (CA, 2007).

     At the global level, inland capture fisheries have been increasing since 1984. In 1997, inland fisheries accounted for 7.7 million tonnes, or almost 12% of total capture available for human consumption, a level estimated to be at or above maximum sustainable yields (Revenga et al., 2000). In 2000-2002, inland capture fisheries were estimated at around 8.7 million tonnes. However, there is still a lack of reliable data on global inland fisheries production, which are therefore estimated to be underreported by two or three times (FAO, 2004b).

     In 2004, aquaculture accounted for 43% of the world's food fish production and is perceived as having the greatest potential to meet the growing demand for aquatic food (FAO, 2006c). World aquaculture has grown at an average annual rate of 8.8% from 1950 to 2004. In recent years, Asia and Africa have shown the highest growth with Latin America displaying only moderate growth. Production in North America, Europe and the former Soviet states has however declined. The average growth rate for the Asia and the Pacific region was 9.8%, while production in China, considered separately, has grown at a rate of 12.4% per year (FAO, 2006c).

     In 2004, freshwater aquaculture was the predominant form of aquaculture, accounting for 56% of the total production while mariculture contributed 36% and brackishwater aquaculture 7.4% (FAO, 2006c). During the last decade, inland capture production has remained relatively stagnant. For instance, during the period 2000-2005, production ranged between 8.8-9.6 million tonnes. During the same period, aquaculture grew from 21.2 to 28.9 million tonnes. Similar trends have been observed in marine environments. Thus overall, the total aquaculture production grew from 35.5 to 47.8 million tonnes. Despite this increase in landings, maintained in many regions by fishery enhancements such as stocking and fish introductions, the greatest overall threat for the long-term sustainability of inland fishery resources is the loss of fishery habitat and the degradation of the terrestrial and aquatic environment.

     About 40% of the world's population lives within 100 km of a coast. Because of the current pressures on coastal ecosystems, and the immense value of the goods and services derived from them, there is an increasing need to evaluate trade-offs between different activities that may be proposed for a particular coastal area. This important habitat is increasingly becoming disturbed due to human activity. Many coastal habitats such as mangroves, wetlands, sea-grasses, and coral reefs, which are important as nurseries, are disappearing at a fast pace. About 75% of all fish stocks for which information is available are in urgent need of better management (Burke et al., 2001; FAO, 2004b).

     A recent assessment of fish stocks by the FAO indicates that only 20% of fish species is moderately exploited and only 3% is underexploited. Of the remaining 76%, 52% of stocks is fully exploited, 17% is overexploited and 7% is depleted (FAO, 2004b).

     Depletion of marine resources is so severe that some commercial fish species, such as the Atlantic Cod, five species of tuna, and haddock are now threatened globally, as are several species of whales, seals, and sea turtles. The scale of the global fishing enterprise has grown rapidly and exploitation of fish stocks has followed a predictable pattern, progressing from region to region across the world's oceans. As each area in turn reaches its maximum production level, it then begins to decline (Grainger and Garcia, 1996).

     Apart from being an important food source, fish can also be a source of contamination. In heavily polluted areas, in waters that have insufficient exchange with the world's oceans, e.g., the Baltic Sea and the Mediterranean Sea, in estuaries, rivers and especially in locations that are close to industrial sites, concentrations of contaminants that exceed natural load can be found. These increasing amounts may