Indicators of Sustainability - Agroecology: The Ecology of Sustainable Food Systems - page 300

T RADITIONAL A GROECOSYSTEMS AS E XAMPLES
OF S USTAINABLE F UNCTION
Throughout much of the rural world today, traditional agri-
cultural practices and knowledge continue to form the basis
for much of the primary food production. What distin-
guishes traditional and indigenous production systems
from conventional systems is that the former developed
primarily in times or places where inputs other than human
labor and local resources were not available, or where
alternatives have been found that reduce, eliminate, or
replace the energy- and technology-intensive human inputs
common to much of present-day conventional agriculture.
The knowledge embodied in traditional systems reflects
experience gained from past generations, yet continues to
develop in the present as the ecological and cultural envi-
ronment of the people involved go through the continual
process of adaptation and change (Wilken, 1988; González
Jácome and Del Amo, 1999) (Figure 21.1).
Many traditional farming systems can allow for the
satisfaction of local needs while also contributing to food
demands on the regional or national level. Production
takes place in ways that focus more on the long-term
sustainability of the system, rather than solely on maxi-
mizing yield and profit. Traditional agroecosystems have
been in use for a long time, and during that time have
gone through many changes and adaptations. The fact that
they still are in use is strong evidence for a social and
ecological stability that modern, mechanized systems
could well envy (Klee, 1980).
Studies of traditional agroecosystems can contribute
greatly to the development of ecologically sound manage-
ment practices. Indeed, our understanding of sustainability
in ecological terms comes mainly from knowledge gener-
ated from such study (Altieri, 1999).
What are the characteristics of traditional agroecosys-
tems that make them sustainable? Despite the diversity of
these agroecosystems across the globe, we can begin to
answer this question by examining what most traditional
systems have in common. Traditional agroecosystems:

TA B L E 2 1 . 1
Properties of Natural Ecosystems, Sustainable
Agroecosystems, and Conventional Agroecosystems

Sustainable
Agroeco-
systems a

Conventiona
l Agroeco-
systems a

Natural
Ecosystems

Production (yield) Low Low/medium High

Productivity (process) Medium Medium/high Low/medium

Diversity High Medium Low

Resilience High Medium Low

Output stability Medium Low/medium High

Flexibility High Medium Low

Human displacement
of ecological
processes

Low Medium High

Reliance on external
human inputs

Low Medium High

Autonomy High High Low

Interdependence High High Low

Sustainability High High Low

a Properties given for these systems are most applicable to the farm
scale and for the short- to medium-term time frame.

Source: Modified from Altieri M.A. 1995b, 2nd ed. Westview Press:
Boulder, CO; Gliessman S.R. 2001, Advances in Agroecology. CRC
Press: Boca Raton, FL.; Odum and Barrett, 2004. Fundamentaly of
Ecology. 5th edition, Thomson Brooks/Cole:Belmont, CA.

Table 21.1 compares these three types of systems in
terms of several ecological criteria. As the terms in the
table indicate, sustainable agroecosystems model the high
diversity, resilience, and autonomy of natural ecosystems.
Compared to conventional systems, they have somewhat
lower and more variable yields, a reflection of the varia-
tion that occurs from year to year in nature. These lower
yields, however, are usually more than offset by the advan-
tage gained in reduced dependence on external inputs and
an accompanying reduction in adverse environmental
impacts.
From this comparison, we can derive a general
principle: the greater the structural and functional
similarity of an agroecosystem to the natural ecosys-
tems in its biogeographic region, the greater the like-
lihood that the agroecosystem will be sustainable . If
this principle holds true, then observable and measur-
able values for a range of natural ecosystem processes,
structures, and rates can provide threshold values, or
benchmarks, that describe or delineate the ecological
potential for the design and management of agroeco-
systems in a particular area. It is the task of research
to determine how close an agroecosystem needs to
be to these benchmark values to be sustainable
(Gliessman, 2001).

• do not depend on external purchased inputs

• make extensive use of locally available and

renewable resources

• emphasize the recycling of nutrients

• have beneficial or minimal negative impacts on

both the on- and off-farm environment

• are adapted to or tolerant of local conditions,

rather than dependent on massive alteration or
control of the environment

• are able to take advantage of the full range of

microenvironmental variation within the crop-
ping system, farm, and region