The Properties of Agroecosystems 127normative indicators of performance, rather than neutral descriptors, then agricul-
tural development will involve significant trade-offs between them. For example, a
large-scale irrigation project may achieve greater overall productivity yet be at the
expense of sustainability and equitability. Similarly, too much emphasis on equita-
bility may inhibit productivity. Within a farm, high stability and sustainability
may depend on a complementary diversity of crop fields and livestock systems,
each of which produces less than its maximal potential and is more variable in yield
and individually less sustainable than is the total farm. A similar situation can
occur between the nation and its agricultural regions.
The trade-offs can be seen clearly in the history of agriculture. Each combina-
tion of properties can be thought of as an agroecosystem strategy, successive phases
of agricultural development reflecting different priorities and hence strategies. The
following selected examples from agricultural history are intended to illustrate
these points.
Table 6.2 Key variables and processes affecting the system properties of villages in
northern areas of Pakistan (after Conway et al, 1985)Positive Negative
Productivity
Construction of Karakoram Highway Shortage of cultivable land
Development of new land Shortage of water
Inorganic fertilizers Weeds, pests and diseases
New wheat and fruit varieties Seasonal labour shortage
Introduction of seed potato cultivation
New credit loan system
Stability
Integration of crops and livestock Crop pests and diseases
Cooperative marketing Livestock diseases
Improvement of irrigation channels Temperature fluctuations
Sustainability
Farmyard manure Glacier movement
Crop rotation (wheat, potatoes) Mudflows, avalanches
Training of village livestock specialists Earthquakes
River bank erosion
Virus of seed potatoes
Overuse of pesticides
Equitability
Traditional cooperation Sale of land
Creation of Village Organizations Education
Rotation of pasturing Emigrant labour
Development of new land