hence the distribution of rainfall (Salati and Vose, 1984). Regional-scale advection of atmospheric moisture is adversely affected by removal of woody vegetation (natural and crops), because of greater water losses to surface runoff, groundwater and a reduction of evaporation and transpiration from the canopy (Salati and Vose, 1984; Rowntree, 1988; Shuttleworth, 1988). Thus the maintenance of perennial vegetation has positive effects on rainfall patterns that enhance hydrological processes (Meher-Homji, 1988) affecting the amount of moisture that can be advected downwind to fall as rain somewhere else (Salati and Vose, 1984). Mixed perennial agricultural systems can probably mimic these hydrological functions of natural forests (Leakey, 1996).

Estuarine habitats are the interface between terrestrial freshwater and marine environments. They are important nursery grounds for the production of commercially important marine fishes, but are subject to detrimental agricultural, urban and industrial developments.

Qualitative evidence of the use of estuarine habitats by juvenile marine fishes is plentiful (Pihl et al., 2002), but recent quantitative research, including stable isotope analysis and otolith chemistry (Hobson, 1999; Gillanders et al., 2003), has confirmed and emphasized the importance of river estuaries in the connectivity between freshwater and marine habitats (Gillanders, 2005; Herzka, 2005; Leakey, 2006). While few marine fish species are considered to be dependent on estuaries, substantial energetic subsidies to fish populations are derived from their juvenile years living and feeding in estuaries (Leakey, 2006). Given the continued vulnerability of estuaries to the loss of water quality from degradation, pollution and other detrimental human impacts, information about the behavior and resource use of juvenile fishes is crucial for future fisheries management and conservation (Leakey, 2006). In the tropics, mangrove swamps are particularly important (Mumby et al., 2004).

3.2.2.2.2 Conserving biodiversity (in situ, ex situ) and ecoagriculture

Biodiversity is the total variation found within living organisms and the ecological complexes they inhabit (Wilson, 1992) and is recognized as a critical component of farming systems above and below ground (Cassman et al., 2005; MA, 2005c). It is important because there are many undomesticated species that are currently either underutilized, or not yet recognized as having value in production systems. Secondly, terrestrial and aquatic ecosystems contain many species crucial to the effective functioning of foodchains and lifecycles, and which consequently confer ecological sustainability or resilience (e.g., regulation of population size, nutrient-cycling, pest and disease control). The conservation of genetic diversity is important because evolutionary processes are necessary to allow species to survive by adapting to changing environments. Crop domestication, like this evolution requires a full set of genes and thus is grounded in intraspecific genetic diversity (Harlan, 1975; Waliyar et al., 2003).

Biological diversity plays a key role in the provision of agroecological function.

Ecological processes affected by agroecosystem biodiversity include pollination, seed dispersal, pest and disease management, carbon sequestration and climate regulation (Diaz et al., 2005; MA, 2005c). Wild pollinators are essential to the reproduction of many crops, especially fruits and vegetables (Gemmill-Herren et al., 2007). To maintain a full suite of pollinators and increase agricultural productivity requires the protection of the habitats for pollinators (forests, hedgerows, etc.) within the agricultural landscape. A number of emerging management approaches to diversified agriculture (ecoagriculture, agroforestry, organic agriculture, conservation agriculture, etc.) seek to preserve and promote biodiversity (described above in 3.2.2.1).

The conservation of biological diversity is important because it benefits humanity.

Humans have exploited plant diversity to meet their everyday needs for food, medicine, etc., for millennia. Agrobiodiversity is increasingly recognized as a tangible, economic resource directly equivalent to a country's mineral wealth. These genetic resources (communities, species and genes) are used by breeders for the development of domesticated crops and livestock (IPGRI, 1993). Species and ecosystems can be conserved for their intrinsic qualities (McNeely and Guruswamy, 1998), but biodiversity conservation is increasingly recognized for its importance in combating malnutrition, ill health, poverty and environmental degradation. Collecting and conserving the world's germplasm in gene banks has been estimated at US$5.3 billion (Hawkes et al., 2000), but the cost is greatly outweighed by the value of plant genetic resources to the pharmaceutical, botanical medicine, major crop, horticultural, crop protection, biotechnology, cosmetics and personal care products industries (US$500-800 billion per year) (ten Kate and Laird, 1999).

Agrobiodiversity is threatened.

Agrobiodiversity is rapidly declining due to the destruction and fragmentation of natural ecosystems, overexploitation, introduction of exotic species, human socioeconomic changes, human-instigated and natural calamities, and especially changes in agricultural practices and land use, notably the replacement of traditional crop varieties with modern, more uniform varieties. Nearly 34,000 species (12.5% of the world's flora) are currently threatened with extinction (Walters and Gillett, 1998), while 75% of the genetic diversity of agricultural crops has been lost since the beginning of the last century (FAO, 1998a). On 98% of the cultivated area of the Philippines, thousands of rice landraces have been replaced by two modern varieties, while in Mexico and