Environmental Management: Principles and practice

Agroecosystem analysis
Basically this is a form of rapid rural appraisal (Conway, 1985a; 1985b; Conway
and Barbier, 1990:162–193) and a type of ecosystem approach. An agroecosystem
is an ecosystem modified by humans in order to produce food or other agricultural.
Four agroecosystem properties were recognized by Conway (1985b):

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1
Productivity—output, yield or net income from a valued product per unit of
resource input. This can be measured as yield or income per hectare, total
production per household or farm, or at a regional or even national scale.
Alternatively, it may be expressed as calories.
2
Stability—the constancy of productivity in the face of climatic fluctuations,
market demand, etc.
3
Sustainability—the capacity of an agroecosystem to maintain productivity in
the face of environmental challenges and degradation arising from its
exploitation.
4
Equitability—the evenness of distribution of the productivity benefits among
humans.
The agroecosystem can be managed in ways that give optimum levels of each of
these properties: maximizing productivity is likely to reduce agroecosystem
sustainability; ensuring sustainability might reduce productivity.
Agroecosystem management
This demands an understanding of ecosystems and of how natural processes are
modified by agricultural objectives. To manage agroecosystems effectively requires
application of knowledge from a range of disciplines, and the approach supports this
(Risser, 1985; Gliessman, 1990). Because the main goal is to improve socioeconomic
conditions, some feel the agroecosystem approach is more socioeconomic than
ecological in orientation (Armitage, 1995).
Landscape ecology approach
The landscape ecology approach focuses on spatial patterns at the landscape scale
(Vink, 1983; Forman and Godron, 1986; Vos and Opdam, 1993; Ze’ev, 1994). The
response of an ecosystem to disturbance frequently depends on its neighbouring
ecosystems: for example, organisms may escape if there are suitable nearby
ecosystems and recolonize after disturbance ceases; also, energy or materials may
be transferred between ecosystems. An ecosystem seldom functions in isolation
and its ability to withstand stress may depend on how a nearby ecosystem is being
managed, or on whether the boundaries are altered—a road or cleared area of
forest may prevent animal or plant dispersal to a favourable alternative site. The
landscape ecology approach extends ecosystem management to a group of more-
or less neighbouring or linked ecosystems (Jensen et al., 1996). An International
Association of Landscape Ecology (UK-based) was founded some years ago to
help advance the field.
GIS and quantitative techniques have been applied to the landscape ecology
approach (and it has also been applied to agroecosystems management and to
conservation) (Hassan and Anglestam, 1991; Turner and Gardiner, 1991; Bunce et
al., 1993; Haines-Younge et al., 1993). Interesting applications of landscape ecology
and GIS have been: the prediction of the occurrence of Lyme Disease, a growing

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public health problem in the USA (New Scientist 15 November 1997), and the spread
of Chagas Disease in South America. In the UK the Countryside Commission has
been exploring the value of landscape character mapping.