Landscape Diversity and Agroecosystem Management - Agroecology: The Ecology of Sustainable Food Systems - page 322

direct agroecosystem context, ecosystem services are
important at a global scale. They regulate the gaseous
composition of the atmosphere (especially through
sequestration of CO2), create and maintain biodiversity,
affect climate and weather, and maintain watershed func-
tion. Table 22.1 provides a list of ecosystem services
important in an agroecosystem context, each paired with
the ecological processes responsible for it.
A natural ecosystem provides ecosystem services
when its biochemical, biophysical, and biological pro-
cesses are functioning in a healthy manner, allowing it
to be biologically productive (Swift et al., 2004). The
same principle holds for agroecosystems. If an agroeco-
system is to be a provider of ecosystem services, it must
be designed and managed so that its diversity, stability,
and complexity approach that of a natural ecosystem.
In other words, increasing agroecosystem diversity
(Chapter 16) and allowing greater successional development
(Chapter 17) are the bases for creating an agricultural
landscape that can attain its potential for full ecosystem
function.

Diversification of agroecosystems, as we know, comes
about through multiple cropping, rotations, fallows,
mulching, minimum tillage, and livestock integration, and
successional development can be achieved through agro-
forestry, more extensive use of perennials, and the creation
of successional mosaics. And when diverse, succession-
ally developed agroecosystems are managed in concert
with the noncrop components of the landscape through
the practices discussed earlier in this chapter, the ecologi-
cal processes of nutrient cycling, population regulation,
and energy exchange are integrated across the whole land-
scape, ensuring the robust functioning from which
ecosystem services arise.
When we use ecologically based management prac-
tices to enhance the ability of agroecosystems to provide
ecosystem services, we are clearly working toward the
goal of agricultural sustainability at the same time. But it
is only when we expand our thinking to the landscape
level that sustainability and ecosystem services converge
with the conservation of biodiversity (Swift et al., 2004).

ROLE OF AGRICULTURE IN PROTECTING
BIODIVERSITY AND ECOSYSTEM
FUNCTION

TA B L E 2 2 . 1
Ecosystem Services and the Ecosystem Processes
that Provide them in an Agroecosystem Setting

Agricultural development has fundamentally changed
the relationship between human culture and the natural
environment. Not long ago in human history, when all
agriculture was traditional and in a small scale, agroeco-
systems were interspersed as small patches across the
larger natural landscape. Managed habitats maintained
the integrity of natural ecosystems while diversifying the
landscape. Today, in contrast, agricultural land uses pre-
dominate, making natural habitats the dispersed patches
over much of the earth's land surface.
As a consequence, much of the terrestrial earth is
now covered by a cultural landscape rather than a natural
one. According to some estimates, 95% of the world's
terrestrial environment is urbanized, managed, or used
in some way for agriculture, animal husbandry, or for-
estry (Daily et al., 2003; Pimentel et al., 1992; Vitousek
et al., 1997). More than half of the land devoted to
agricultural production depends on large-scale, intensive,
monocultural, or irrigated management, maintaining
very little if any of the ecological processes characteristic
of the natural landscape that preceded it. Less than 5%
of the world's terrestrial surface area is in protected parks
or preserves (Figure 22.7).
On an earth with a cultural landscape, efforts to
preserve our remaining ecosystem diversity can no
longer be focused primarily on the small areas of land
that are still wild. Managed lands, particularly those that
are agricultural, have an enormous untapped potential
for supporting a diversity of native species and providing

Ecosystem Services Responsible Ecosystem Processes

Production of food Primary production, herbivore

consumption, pollination

Production of fiber
and latex

Primary production, secondary
metabolism

Production of
pharmaceuticals

Secondary metabolism

Production of
agrochemicals

Secondary metabolism

Nutrient cycling Herbivore consumption, predation,

decomposition, mineralization, other
elemental transformations

Regulation of water
flow and storage,
flood control

Soil organic matter synthesis, physical
and biological soil processes, plant
growth above and below ground

Regulation of soil and
sediment movement,
erosion control

Soil organic matter synthesis, physical
and biological soil processes, plant
growth above and below ground

Regulation of biological
populations

Plant secondary metabolism,
pollination, herbivory, parasitism,
microsymbiosis, predation

Water and soil purification Metabolism, decomposition, elemental

transformations

Regulation of atmospheric
composition and climate

Photosynthesis, metabolism, and
primary production

Source: Modified from Swift, M. J., A. M. N. Izac and M. van
Noordwijk. 2004. Agri Ecosyst Environ 104: 113-134.