ECOSYSTEM SERVICES
Ecosystems have been described as the life support system of globally usable freshwater supplies comes from forested catch-
the Earth – for humans as well as all life on this planet (MA ments (Fischlin et al., 2007), therefore water is critically linked
Health Synthesis Report 2005). Ecosystem services, the bene- to forests. These ecosystems also help buffer global climate
fits that humans derive from ecosystems, are considered “free”, change (Nepstad et al., 2007).
often invisible, and are therefore not usually factored into de-
cision-making. This chapter discusses the role of the diverse Genetic diversity plays a critical role in increasing and sustain-
forms of living species – biodiversity – in food production, fo- ing food production levels and nutritional diversity. Diverse
cusing on agriculture and marine capture fisheries, as these organisms contributing to soil biodiversity perform a number
provide the bulk of global food production. of vital functions that regulate the soil ecosystem, including de-
composition of litter and cycling of nutrients such as nitrogen.
Agriculture (livestock and foodcrops) require a range of con- Crop rotations or agroforestry increase yield stability and soil
ditions for optimum productivity. These conditions are gener- fertility; grassland and pasture/crop systems tend to be more
ated by natural ecological components and processes as well as sustainable because they provide opportunities for rotation di-
through artificial enhancement. versity. Biodiversity may create “pest suppressive” conditions
and greater resistance to invasion of farming systems by nox-
Water resources for agriculture are highly dependent on natu- ious species. Pollinators are essential for the production of a
ral ecosystems and biodiversity, in particular vegetation such as large number of crops (e.g., cereal, orchard, horticultural and
forests in terms of flow regulation. This is crucial for providing forage production), and contribute to improvements in qual-
a dependable water supply to crop areas, such as through reten- ity of both fruit and fiber crops; this service is ensured by an
tion of water in wetlands and forests buffering both droughts abundance and diversity of pollinators, in large part provided
and floods (Bruijnzeel, 2004; UNEP, 2005). At present 75% of by wild biodiversity.
Pest control is another key ecosystem service underpinned by
biodiversity; it is greatly determined by the abundance of natural
enemies of the pest species involved.Improved pest control is
dependent on a diversity of natural enemies of pests, and non-
crop habitats are fundamental for the presence and survival of
these biological control agents (predators, parasitoids) (Zhang
et al., 2007). Landscape diversity or complexity, and proximity
to semi-natural habitats tend to produce a greater abundance
and species richness of natural enemies (Bianchi et al., 2006;
Kremen and Chaplin-Kramer 2007; Tscharntke et al., 2007;
Balmford et al., 2008). Thus, the main threat to the provision of
biological control as an ecosystem service seems to be habitat
loss and degradation, now exacerbated by potentially disruptive
climate change. Indeed, Balmford et al., (2008) suggest that
there is a medium to high probability that the provisioning of
biological control is subject to thresholds/tipping points in the
foreseeable future (by 2025), particularly in regions of very in-
tensively managed agriculture.
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