Indicators of Sustainability - Agroecology: The Ecology of Sustainable Food Systems - page 299

21 Indicators of Sustainability

What is a sustainable agroecosystem? We answered this
question in the abstract in Chapter 1. A sustainable agro-
ecosystem is one that maintains the resource base upon
which it depends, relies on a minimum of artificial inputs
from outside the farm system, manages pests and diseases
through internal regulating mechanisms, and is able to
recover from the disturbances caused by cultivation and
harvest.
It is a different matter, however, to point to an actually
existing agroecosystem and identify it as sustainable or
not and determine why, or to specify exactly how to build
a sustainable system in a particular bioregion and socio-
cultural context. Generating the knowledge and expertise
for doing so is one of the main tasks facing the science
of agroecology today, and is the subject to which this
chapter is devoted.
Ultimately, sustainability is a test of time: an agro-
ecosystem that has continued to be productive and support
local livelihoods for a long period of time without degrad-
ing its resource base — either locally or elsewhere — can
be said to be sustainable. But just what constitutes “a long
period of time”? How is it determined if degradation of
resources has occurred? What tells us that all the compo-
nents of the system are healthy and viable? How well
integrated are the social and ecological components of
sustainability? And how can a sustainable system be
designed when the proof of its sustainability remains
always in the future?
Despite these challenges, we need to determine what
sustainability entails. In short, the task is to identify
parameters of sustainability — specific characteristics of
agroecosystems that play key parts in agroecosystem func-
tion — and to determine at what level or condition, and
for how long, these parameters must be maintained for
sustainable function to occur. Through this process, we
can identify what we will call indicators of sustainability
— agroecosystem-specific conditions necessary for and
indicative of sustainability. With such knowledge it will
be possible to predict whether or not a particular agro-
ecosystem can be sustained over the long term, and to
design agroecosystems that have the best chance of prov-
ing to be sustainable. This knowledge will also help us
work to change the external forces that have kept most
agroecosystems from being sustainable in the first place.

LEARNING FROM EXISTING SUSTAINABLE
SYSTEMS

The process of identifying the elements of sustainability
begins with two kinds of existing systems: natural ecosys-
tems and traditional agroecosystems. Both have stood the
test of time in terms of maintaining productivity over long
periods, and each offers a different kind of knowledge
foundation. Natural ecosystems provide important refer-
ence points, or benchmarks, for understanding the ecologi-
cal basis of sustainability; traditional agroecosystems offer
abundant examples of actually sustainable agricultural
practices as well as insights into how social systems —
cultural, political, and economic — fit into the sustain-
ability equation. Based on the knowledge gained
from these systems, agroecological research can devise
principles, practices, and designs that can be applied in
converting unsustainable conventional agroecosystems
into sustainable ones.

N ATURAL E COSYSTEMS AS R EFERENCE P OINTS

As discussed in Chapter 2, natural ecosystems and con-
ventional agroecosystems are very different. Conven-
tional agroecosystems are generally more productive but
far less diverse than natural systems. And unlike natural
systems, conventional agroecosystems are far from self-
sustaining. Their productivity can be maintained only
with large additional inputs of energy and materials from
external, human-produced sources; otherwise they
quickly degrade to a much less productive level. In every
respect, these two types of systems are at opposite ends
of a spectrum.
The key to sustainability is to find a compromise
between the two — a system that models the structure and
function of natural ecosystems yet yields a harvest for
human use. Such a system is manipulated to a high degree
by humans for human ends, and is therefore not self -
sustaining, but relies on natural processes for maintenance
of its productivity. Its resemblance to natural systems
allows the system to sustain, over the long term, human
appropriation of its biomass without large subsidies of
industrial cultural energy and without detrimental effects
on the surrounding environment.

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