Indicators of Sustainability - Agroecology: The Ecology of Sustainable Food Systems - page 309

markets, and pesticide use has been gathered from multi-
ple agencies and organizations connected to agriculture
and food issues. Data sets for some factors come from
many years of data gathering and have considerable quan-
titative validity. They can be used to project forward into
the future the kinds of changes that might be needed to
offset negative trends, or to promote more sustainable
activities, practices, or policies. These data sets, however,
are limited in two ways: they have focused on the current
food system, not the one we want to move toward, and
they are not very well integrated and able to give a full
view of how the component parts of a sustainable food
system might be assembled.
An approach that can begin to overcome this prob-
lem and better integrate the separate parameters of
sustainability is the system Marco para la Evaluación
de Sistemas de Manejo de Recursos Naturales (MESMIS)

for evaluating natural resource management systems,
developed by Masera and others in Mexico (Masera and
Lopéz-Ridaura, 2000). Indicators are chosen, ideal val-
ues for each are determined, and two or more systems
are analyzed to determine how close, in percentage
terms, each aspect of the system comes to the ideal
value set for its indicator. The result is an “amoeba”
diagram, or radar graph, like the one shown in
Figure 21.3. The assumption is that the greater the per-
centage of the optimal area covered by an amoeba the
higher the level of sustainability of the agroecosystem
it represents. Areas of relative strength and weakness
can thereby be compared. This system can be used to
show how close each indicator is to a theoretically ideal
value, offering a measure of progress toward sustain-
able function. Both qualitative and quantitative
measures can be used. In addition, when applied in a

SUSTAINABILITY IN A CHINESE VILLAGE AGROECOSYSTEM

Although it is often easy to identify processes that are degrading a system, it is much more difficult to determine
what processes are necessary for sustainable productivity. Because the term “sustainable” describes a managed
system that will maintain productivity over an indefinite period of time, it is difficult to find indicators of sustain-
ability that can be measured over the short term.
One way to look for these indicators is to study systems that have a track record, systems that have sustained
constant production of food for human consumption over a long period of time without degrading their ecological
foundations. Many types of traditional agriculture around the world meet this requirement, but their relevance for
the study of ecological sustainability is limited because their yields are much lower than those of modern systems.
Not so for village agroecosystems in the Tai Lake region of China, located in the Yangtze River Delta. Sustained
high yields under intensive human management have been documented in this area for more than nine centuries.
The suitability of these systems for study of sustainability attracted researcher Erle Ellis in the 1990s.
Since traditional management practices have now in part been supplanted by modern practices, Ellis looked at
the history of the region's agriculture, examining a multitude of factors, including landscape features, climate, soils,
and human management practices. In order to elucidate the ecological mechanisms underlying the sustainability of
the area's agriculture, Ellis studied the cycling of nutrients at the level of an entire village. This scale of study
allowed him to compensate for the variability that exists between the practices of individual farmers and the
variability of the landscape, and thereby draw more accurate conclusions. It also enabled him to discern overall
processes that might be invisible at the field level.
With evidence suggesting that nitrogen was the limiting factor in traditional Chinese agroecosystems, Ellis made
the cycling and management of this nutrient the focus of his research. He identified the specific practices and natural
processes in the system that historically maintained adequate levels of soil nitrogen in the absence of inputs of
inorganic fertilizer.
Ellis identified several aspects of traditional management practices that he believes were essential in maintaining
nitrogen fertility (Ellis and Wang, 1997). One of the most important of these was the use of natural inputs, such as
sediments from local waterways. Biological nitrogen fixation also played a significant role. A third factor, perhaps the
most important, was the thorough recycling of organic matter. Nearly all organic wastes — including human
excrement — were recycled in the village system, either by being returned to the fields directly or composted and
then returned. Another important contributor to sustainability was the integration of animals to create a cyclical nutrient
flow: farmers raised pigs specifically for their manure, and a portion of the animals' diet was food and agricultural waste.
Although these practices continue, they have been largely replaced by the application of inorganic fertilizers.
This change, initiated in the 1960s, has made nitrogen a problematic source of pollution instead of a limiting nutrient.
Although the use of inorganic inputs has boosted productivity even higher, feeding an ever-growing population, this
change in management makes the continued sustainability of the region's agricultural systems an open question.