Landscape Diversity and Agroecosystem Management - Agroecology: The Ecology of Sustainable Food Systems - page 320

FIGURE 22.5 A second-growth edge habitat at Finca Loma Linda, Coto Brus, Costa Rica. Low, diverse vegetation at the forest
edge can serve as a habitat for beneficial organisms that, once established there, can move out into the crops.

THE AGRICULTURAL LANDSCAPE AS A
PROVIDER OF ECOLOGICAL SERVICES

existing in one patch may be isolated from other popula-
tions; unless frequent interchange of individuals can occur
between patches, each subpopulation can become subject
to either genetic isolation or extirpation.
Because natural ecosystem patches provide refugia for
agriculturally beneficial organisms and can provide vari-
ous other environmental services, there is considerable
advantage in determining the optimum density, abun-
dance, and configuration of natural ecosystem patches in
relation to areas of agricultural production. Corridors linking
habitat patches may be necessary for facilitating movement
of beneficial organisms across the landscape. A certain
width of edge may provide the optimal edge effect without
creating pest problems for both natural and agricultural
systems. Promoters of integrated pest management often
claim that successful pest management without the use of
pesticides will require regional or landscape-level man-
agement programs that strive to take advantage of both
the isolating mechanisms and facilitating mechanisms of
a patchy environment (Settle et al., 1996). Ecologists are
being called upon to apply their knowledge of ecological
processes in natural ecosystems to solving such problems
(Kareiva, 1996).

When the agricultural landscape is viewed as an integrated
whole, combining all of the nonfarmed and farmed areas
in a region, it can be managed so that it functions as an
integrated ecosystem and provides environmental services
in much the same way that natural ecosystems would
provide alone. The agroecological knowledge and prac-
tices described in Sections II and III of this topic provide
much of the theoretical and practical basis of this
management.
Environmental services are the many “goods” and ser-
vices provided by natural ecosystems that are essential
for human survival and welfare and the global biosphere
(Costanza et al., 1997; Matson et al., 1997; Millennium
Ecosystem Assessment, 2003). Until recently, we have
tended to take them for granted because they are perceived
as free and abundant. Ecosystem services that are particu-
larly important for sustainable agroecosystem function
include nutrient cycling, biological control of pests and
diseases, erosion control and sediment retention, water regu-
lation, and maintenance of the genetic diversity essential
for successful crops and animal breeding. Outside of the