From Sustainable Agroecosystems to Sustainable Food Systems - Agroecology: The Ecology of Sustainable Food Systems - page 346

is harnessed and affected by the process. A number of
researchers have developed theoretical models that help
us conceptualize these complex relationships. These mod-
els offer alternative conceptions of how agroecosystems
exist in the intersection between nature and society —
how they come about and change as a result of a complex
interaction between ecological and social/economic fac-
tors. And each model suggests particular requirements for
sustainability. Three of these models are presented below.
In the 1970s, when agriculture was dominated by
Green Revolution thinking and most farmers and research-
ers were ignoring both the ecological basis of agriculture
and its social ramifications, the Mexican agronomist and
ethnobotanist Efraím Hernandéz Xolocotzi introduced a
model that pictured agroecosystems as the outcome of
constant coevolution between ecological, technological,
and socioeconomic factors (Figure 24.4). Each factor
influences the design and management of the agroecosys-
tem while simultaneously interacting with the others. A
complex set of feedbacks between factors and influences
shapes the agroecosystem over time. Implicit in this model
is the notion of balance, and imbalance becomes a matter
of concern and a barrier to sustainability. For example, if
market demands (a socioeconomic factor) cause farmers
to put irrigation (a technological factor) into place so that

limited rainfall (an ecological factor) can be ignored, the
system can be thrown out of balance. The factor interac-
tion may be confined to a back and forth interplay between
socioeconomic pressures and technological fixes, and
ecological sustainability is sacrificed.
Cornelia Flora offers a model focused on the rural
communities in which agricultural production is based. In
her model (Figure 24.5), agroecosystems come about as
human communities use the potential of the local landscape
to extract value and maintain themselves. In this process,
they use four basic types of resources. Since these basic
resource types are used to create new resources, she defines
them as forms of capital. As with the Hernandez X. model,
balance is required for sustainability. Specifically, all four
forms of capital must be constantly replenished, not
depleted. For example, a strategy that emphasizes the short-
term accumulation of financial capital through intensive
irrigated agriculture can decrease natural capital by causing
salinization or loss of natural wetlands.
From the perspective of environmental sociology, Gra-
ham Woodgate proposes a model in which nature (the
ecological foundation of agroecosystems) is wholly
enclosed within society, and the relationship between the
two recalls the coevolution of Herndandez X.'s model. In
this model, agroecosystems — which occupy the interface

Ecological
factors

Agroecosystem

Socio-economic
factors

Technological
factors

FIGURE 24.4 Efraím Hernandéz Xolocotzi's model of the factors influencing the design and management of agroecosytems.
[Modified from Hernandez Xolocotzi, E. (ed.) 1977. Agroecosistemas de México: Contribucciones a la Enseñanza, Investigación, y
Divulgación Agrícola . Colegio de Postgraduados: Chapingo, México.]

Human
Capital

Social
Capital

Communities
healthy ecosystems
vital economy
social equity

Financial/
built
Capital

Natural
Capital

FIGURE 24.5 Cornelia Flora's model of agroecosystems as products of human communities mediated by factors conceived
as varying forms of capital. [Modified from Flora, C. ed., 2001. Interactions between Agroecosystems and Rural Communities .
Advances in Agroecology. CRC Press: Boca Raton, FL.]