Landscape Diversity and Agroecosystem Management - Agroecology: The Ecology of Sustainable Food Systems - page 315

A B C

Natural ecosystem

Areas of moderate or reduced human distrubance

Areas of agricultural production

FIGURE 22.2 Examples of three common patterns in the arrangement of the components of the agricultural landscape.
A natural ecosystem and an agroecosystem can be separated by an area of intermediate human influence (a); a natural ecosystem
can form a corridor, strip, or patch within an agroecosystem (b); and areas of less-intense human management can be dispersed
within a larger area of agricultural production (c).

The heterogeneity of the agricultural landscape varies
greatly by region. In some parts of the world (e.g., the
Midwestern U.S.), the heavy use of agricultural chemicals,
mechanical technology, narrow genetic lines, and irriga-
tion over large areas have made the landscape relatively
homogenous. In such areas, the agricultural landscape is
made up mostly of large areas of single-crop agricultural
production. In other areas (e.g., the Jiangsu Province of
the Yangtze in China), the use of traditional farming prac-
tices with minimal industrial inputs has resulted in a varied,
highly heterogeneous landscape — possibly even more
heterogeneous than would exist naturally.
The typical agricultural landscape, because of its
mosaic makeup, is ecologically a fragmented environ-
ment. Each patch is a fragment, isolated from other similar
patches by some other type of ecologically dissimilar com-
munity. On one hand, this fragmentation can have negative
effects on populations restricted to a particular type of
habitat. On the other hand, a fragmented, heterogeneous
landscape has high gamma diversity. As we will explore
in the next section, effective management at the level of
the landscape involves enhancing gamma diversity and
taking advantage of its benefits, while at the same time
mitigating the possible negative consequences of habitat
fragmentation.

known as landscape ecology . Because it helps us under-
stand how the different parts of the landscape mosaic are
formed and how they interact, landscape ecology provides
a good basis for management of the agricultural landscape
(Turner et al., 2001; Odum and Barrett, 2004).
Three important tools of landscape ecology are aerial
photography, satellite imagery, and geographic informa-
tion system (GIS) analysis. Using these tools, present
landscape patterns can be contrasted with those that were
observed in the past. The changes that have occurred can
then be correlated with farming systems data to understand
the role of agroecosystems in maintaining the stability and
sustainability of landscape systems, which provides a
basis for designing management schemes that take into
account all landscape elements (Ellis, 2004).
Any form of historical data on landscape patterns can
be useful in analyzing the agricultural landscape. Census
data, such as that from the U.S. Census of Agriculture,
can be particularly important in determining the types of
crops that have been grown in a region and where they
were grown. These data can be given quantifiable values
when combined with aerial photographs, allowing the analyst
to determine the number of landscape elements present at
different times (e.g., crop fields, pastures, riparian corri-
dors, and forest patches). When these data are subjected
to GIS analysis, they can become a dynamic way of visu-
alizing the patterns and relationships of landscape struc-
ture through time.
For example, the GIS images in Figure 22.3 show
changes that have occurred over several decades in an
agricultural region of Guangdong Province in China. As
this region underwent a shift from a primarily agricultural
economy to a more industrialized economy, agricultural
land underwent significant change. Through a combina-
tion of forest recovery, planted forestry, and the develop-
ment of orchard crops, woody vegetation recovered, and

A NALYZING THE L ANDSCAPE

At the landscape level, the movement of organisms and
substances between habitat patches becomes a critical
factor in the maintenance of overall ecological processes.
Also important is the interaction of organisms and physi-
cal processes located in different habitat patches. What
happens in one area of the landscape can have an impact
on other areas. The study of these factors, and how they
are shaped by the spatial patterning of the landscape, is