Agro Ecosystems

As the term clearly implies, an agro-ecosystem is an ecosystem within the conceptual and biological boundaries of agriculture. It is a natural ecosystem that has been modified by our own cultural developments. It has many of the characteristics of a wild ecosystem, but it differs in the control exerted over it by people. This human aspect of agro-ecosystems cannot be over emphasised. Both farmers and agricultural scientists are components of the agro-ecosystem. So too are amateur plant breeders. So too are the fertiliser and pesticide manufacturers, and their salesmen.

The control exerted by these various people leads to the cultivation of domesticated species of plants and animals, usually in homogeneous populations, in an environment modified by human activities such as clearing, cultivation, artificial fertilisers, irrigation, weeding, and crop protection chemicals.

There are nearly as many different agro-ecosystems as there are wild ecosystems. Climate is probably the most important of the factors that determine what crops can be grown, and agro-ecosystems are often named after their predominant crop. Thus, we speak of the 'corn belt', 'wheat-lands', 'coffee country', 'cocoa climate', etc. Within these broad divisions are many subdivisions, often defined by the epidemiological competence of crop parasites.

In the context of crop parasites, the formal definition of an agro-ecosystem is the area in which one horizontally resistant cultivar can be cultivated without crop protection chemicals, and without significant loss from parasites. That is, each of the many different horizontal resistances of the cultivar, to its many different parasites, is in balance with the epidemiological competence of each of those parasites, in that agro-ecosystem.

As the title of this book implies, it is now suggested that our agro-ecosystems should be allowed to self-organise, in the same way that Adam Smith recommended that markets should be allowed to self-organise (see 11).

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