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66

ECOSYSTEM SERVICES

Ecosystems have been described as the life support system of

the Earth – for humans as well as all life on this planet (MA

Health Synthesis Report 2005). Ecosystem services, the bene-

fits that humans derive from ecosystems, are considered “free”,

often invisible, and are therefore not usually factored into de-

cision-making. This chapter discusses the role of the diverse

forms of living species – biodiversity – in food production, fo-

cusing on agriculture and marine capture fisheries, as these

provide the bulk of global food production.

Agriculture (livestock and foodcrops) require a range of con-

ditions for optimum productivity. These conditions are gener-

ated by natural ecological components and processes as well as

through artificial enhancement.

Water resources for agriculture are highly dependent on natu-

ral ecosystems and biodiversity, in particular vegetation such as

forests in terms of flow regulation. This is crucial for providing

a dependable water supply to crop areas, such as through reten-

tion of water in wetlands and forests buffering both droughts

and floods (Bruijnzeel, 2004; UNEP, 2005). At present 75% of

globally usable freshwater supplies comes from forested catch-

ments (Fischlin

et al

., 2007), therefore water is critically linked

to forests. These ecosystems also help buffer global climate

change (Nepstad

et al

., 2007).

Genetic diversity plays a critical role in increasing and sustain-

ing food production levels and nutritional diversity. Diverse

organisms contributing to soil biodiversity perform a number

of vital functions that regulate the soil ecosystem, including de-

composition of litter and cycling of nutrients such as nitrogen.

Crop rotations or agroforestry increase yield stability and soil

fertility; grassland and pasture/crop systems tend to be more

sustainable because they provide opportunities for rotation di-

versity. Biodiversity may create “pest suppressive” conditions

and greater resistance to invasion of farming systems by nox-

ious species. Pollinators are essential for the production of a

large number of crops (e.g., cereal, orchard, horticultural and

forage production), and contribute to improvements in qual-

ity of both fruit and fiber crops; this service is ensured by an

abundance and diversity of pollinators, in large part provided

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.