Landscape Diversity and Agroecosystem Management - Agroecology: The Ecology of Sustainable Food Systems - page 313

22 Landscape Diversity and Agroecosystem

Management

Since the beginning of agriculture, agroecosystems have
been altering and displacing naturally occurring terrestrial
ecosystems across the face of the earth. The ongoing pro-
cess of converting land to agricultural production has had
a dramatic and usually negative impact on the diversity of
organisms and the integrity of ecological processes.
Although other forms of human exploitation of the envi-
ronment, such as urbanization and mining, have also con-
tributed to large-scale habitat modification and the loss of
biodiversity and ecosystem function, agricultural produc-
tion — including grazing and timber production — bears
much of the responsibility for causing environmental
changes at the biosphere scale that threaten the world's
life-support systems.
One of the major goals of developing a sustainable
agriculture is to reverse this legacy of destruction and
neglect, to conserve biotic resources and protect environ-
mental quality. Indeed, this goal is built into our definition
of agricultural sustainability. More-sustainable agroeco-
systems — more diverse, relying less on external inputs
and intensive modification of the environment — will, by
their very nature, be more environmentally friendly.
However, a variety of important management principles
come to light when we focus on the relationship between
agroecosystems and natural ecosystems. In particular, we find
that crops and farms can benefit as much as natural ecosys-
tems when we design and manage agroecosystems with natu-
ral habitats, native species, and regional ecological processes
in mind. Carrying out agricultural production so that it works
with, rather than against, natural ecosystem processes is nec-
essary not just for the sake of the natural environmental itself,
but for the long-term welfare of human society. We depend
on healthy, functioning ecosystems to moderate weather
extremes, cycle nutrients, protect riverbanks from erosion,
filter our drinking water, detoxify our waste water, generate
new soil, pollinate crops, reduce the impacts of droughts and
floods, and provide us with a variety of other ecosystem
services . By replacing most of the earth's natural environ-
ments with systems managed for agricultural and timber pro-
duction, we have seriously threatened the foundations of
these ecosystem services. From a sustainability perspective,
therefore, we must work toward two goals: (1) protect
remaining natural environments, ecosystems, and biodiver-
sity from the effects of our intensive management, and (2)
design and manage agroecosystems so that they can function
as providers of ecosystem services themselves.

THE AGRICULTURAL LANDSCAPE

Developing agroecosystems that protect and enhance
biotic diversity and ecological processes — and in turn
derive benefits from the natural environment — requires
a shift of perspective to the regional or landscape level.
So first we will examine the basic aspects of the agricul-
tural landscape.
Agricultural development within a formerly natural
environment tends to result in a heterogeneous mosaic of
varying types of habitat patches spread across the land-
scape. The bulk of the land may be intensely managed
and frequently disturbed for the purposes of agricultural
production, but certain parts (wetlands, riparian corridors,
and hillocks) may be left in a relatively natural condition,
and other parts (borders between fields, areas around
buildings, roadsides, and strips between fields and adja-
cent natural areas) may occasionally be disturbed but not
intensely managed. In addition, natural ecosystems may
surround or border areas in which agricultural production
dominates.
Although the level of human influence on the land
varies on a continuum from intense disturbance and man-
agement to relatively pristine wildness, we can divide this
continuum into three sections to derive three basic kinds
of components of the agricultural landscape:

1. Areas of agricultural production. Intensely

managed and regularly disturbed, these areas
are made up mainly of nonnative, domesticated
plant species.

2. Areas of moderate or reduced human influ-

ence. This intermediate category includes
pastureland, forests managed for timber
production, hedgerows and other border
areas, and agroforestry systems. These areas
are typically made up of some mixture of
native and nonnative plant species and are
able to serve as habitat for many native ani-
mal species.

3. Natural areas. These areas retain some resem-

blance of the original ecosystem structure and
species composition naturally present in the
location, although they may be small in size,
contain some nonnative species, and be subject
to some human disturbance.

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