General Introduction - Integrated Assessment of Health and Sustainability of Agroecosystems - page 13

vulnerability as indicators of soil conservation impact. They indicated that a partici-
patory approach was used to elicit information but not how these data were objectively
reorganized into such compound attributes as resource degradation, resilience, and
vulnerability. Lightfoot and Noble (1993), based on a farming systems approach,
focused on integration, efficiency, and recycling. Their list of indicators includes
the number of interlinkages between and within systems, labor allocation, and the
quantity of bioresources flowing between resource systems.
It can be argued that some “nonquantifiable” indicators provide more impor-
tant information than more objective ones (Harrington, 1992). But, if the aim of
a health assessment is to detect changes in the health status of agroecosystems, to
compare one system with another, or to assess the potential impact of various factors
on health, indicators must be amenable to an objective assessment. In addition, the
choice of indicators must be tempered by practicality and the cost of measurement
in terms of time and money. An assessment may be categorized as either descriptive
or predictive of the system's health status (Ruitenbeek, 1991). The purpose of an
assessment may be to assist management and decision making, set policy standards,
determine policy compliance, or assess progress toward a goal (Boyle et al., 2001).
The level of precision required may vary based on the purpose of the assessment as
well as who the end user is.

1.5 tHe KIambu aGRoecosystem

1.5.1 e x t e r n A l e n v i r o n m e n t
Only a third of Kenya is arable, and a shortage of suitable farmland is a severe
constraint to the expansion of agricultural production. An ever-increasing human
population further worsens this situation. In an attempt to increase per capita food
production, two strategies have been sought (Food and Agricultural Organisation,
1981; Government of Kenya, 1983). One is to intensify production on cultivated
lands; the other is to extend cultivation to marginal areas. It is now apparent that the
low fertility of marginal areas allows little or no surplus to be produced (Mohamed-
Saleem and Fitzhugh, 1995). In addition, these environments are too fragile to sup-
port more intensive and long-term agricultural production (Mwonga and Mochoge,
1989). Intensification in the zones of high agricultural potential remains the alterna-
tive with minimum environmental and social costs (Winrock International, 1992).
With a favorable high-altitude climate and a highly diversified agricultural
system (Odingo, 1971), the Kenyan highlands are the most productive lands in the
country. Scarcity of arable land, the high human population, and traditional prac-
tices continue to encourage subdivision of the farmlands into small units. Because
of this and other sociocultural factors, smallholder farms dominate land use in the
highlands and represent the largest farming population in the country (Woomer,
1992). In 1983, it was estimated that there were about 1.5 million smallholders in the
country (Stotz, 1983).
Most of the land in smallholder farms is permanently under crops. This gener-
ally involves the continuous cultivation of maize (Ransom et al., 1995). Most small-
holders in the highlands own and manage animals (Powell and Williams, 1993).