Chapter 2 described the basic physical sources of seasonality and the way in which these manifest themselves in broad climatic patterns. Were these the only sources of seasonality in agricultural production conditions, it would indeed be difficult to design counter-seasonal production strategies on a less than continental scale. Fortunately, the impact of climate is strongly influenced by the environment in which it takes effect, so that seasonal diversity in production possibilities may exist within a relatively small area. Unfortunately, not all of the diversity created by environment is favourable, for pests and diseases of crops, livestock and people are also environmental variables. Some understanding of such relationships is necessary, as a first step towards understanding the technical basis for meeting the challenge of seasonality. (Social factors are considered in later chapters.)

Environment can modify climate, and so help determine production conditions in agriculture, in at least four different ways. First it can modify climate itself, as in the case of orographic lifting and the rain shadow effect discussed in Chapter 2. Second, such features of the physical environment as rocks, soils and landforms, can modify the biological effects of a given climatic regime – as can features of the biological environment itself, such as trees. Third, different species – indeed different varieties of the same species – which themselves form part of the biological environment, react differently to any given combination of climate and physical environment, so that their combined impact on agriculture may in turn be modified.