General Introduction - Integrated Assessment of Health and Sustainability of Agroecosystems - page 5

sustainability (Harrington, 1992). Some problems, such as soil nutrient depletion,
are best studied over the medium term. Some, such as erosion and salinization, are
best studied over longer time frames (Harrington, 1992).
Last, sustainability can be realized (and measured) at several different levels. In
agriculture, such levels could include the plot, the farm, village, catchment, geopolit-
ical or geoclimatic zones, national, and finally global. The various levels are nested
within each other, forming a conceptual hierarchy of concentric layers. Although
the sustainability of a specific level in the hierarchy is directly related to the func-
tional state of the sublevels within it, not all the sublevels need be sustainable. Some
resources may be used in excess of sustainable levels in some units, and the overall
sustainability of the system may be maintained by substituting among resources and
between sublevels over time (Graham-Tomasi, 1991).

1.3.2 A s s e s s m e n t A n D i m p l e m e n t A t i o n

The inability to find a concise definition of sustainability has been viewed as the
obstacle in integrating sustainability concerns in practical decision making (Pearce
et al., 1990; Izac and Swift, 1994; Lynam and Herdt, 1989; Graham-Tomasi, 1991). It
has been argued that scientific research necessitates refining holistic concepts such
as sustainability to a more specific and rigorous one (Izac and Swift, 1994; Pearce
et al., 1990). The countering argument is that various components and factors in
such complexes as agricultural systems have extensive, complex, and dynamic inter-
relationships. Any activity or reaction therefore has a high degree of unpredictabil-
ity on both the spatial and temporal scales (Holling, 1986, 1992). Furthermore, the
action-reaction chain flows—in most cases—in the stochastic, nondeterministic, and
often counterintuitive fashion characteristic of soft systems. Attempts at assessing
agricultural sustainability as if it is an objectively verifiable state of a nonhierarchi-
cal hard system can therefore only result in a great deal of frustration and confusion
(Waltner-Toews, 1996).
The use of indicators to assess sustainability is a widely accepted approach
(Swindale, 1992; Izac and Swift, 1994; Winograd, 1994; van Bruschem, 1997; Aldy
et al., 1998; Smit et al., 1998). There have been attempts to develop generic indica-
tors of sustainability. Such processes have been complicated by the fact that sus-
tainability issues are system and scale specific. The choice of indicators and their
interpretation depend largely on the context in which they are used. What is needed
to implement the broad ideas about sustainability is not so much another list of indi-
cators to measure, but an integrated framework within which such indicators can be
developed and interpreted (Waltner-Toews, 1991).

1.4 aGRoecosystem HealtH
Ecosystem health is an emerging science paralleling human and veterinary medi-
cine with, as its goal, the systematic diagnosis and treatment of stressed agroecosys-
tems (Schaeffer, 1991). It extends and modifies the concept of sustainable agriculture
(Waltner-Toews, 1994) to provide a systematic method for diagnosis, prognosis, and
rehabilitation of agricultural ecosystems (Rapport, 1995).