Agricultural pressures on the ECO system

In any one place over short periods of time in the absence of modern agriculture, there is a more or less balanced population of plants and animals living on and in a given soil type. More or less because climatic conditions are not static and change with time. The flora and fauna and composition of the soil respond to these changes both in terms of the existing population of animals and plants and by genetic variation giving rise to new varieties, species, and so on. A “short period of time” could be as little as a few years.