Various meanings are attributed to the word ‘constraint’. In its commonest definition, the notion is synonymous with constraining, and hence, the constraint appears ‘in opposition’ to something. In the theoretical framework of possibilism, constraint is a limiting factor, which society must either adapt to or overcome.
In mechanics, the word constraint is used to qualify any "magnitude measuring a superficial interaction", and in this case, the interaction may be positive or negative-or even null. Thus, extending this meaning to interactions in a territorial system makes it possible to deal simultaneously with an event and with its impact on society. (Marchand 1980) A period of summer drought in the ‘Midi aquitain’ may be a disaster for corn as well as a blessing for Sauternes wines, etc.
Constraints of Nature belong to two types of dynamics: a spatial one involving expanse, conflicts, and pioneer fronts, and another, temporal one, which expresses the differentiated speeds of vegetation growth or of physico-chemical mechanisms. In the field of climate, a classic distinction is made between static and dynamic constraints. The former express interactions between the socio-economic environment and the physical environment. They feature relative stability over time and/or regular occurrence, and society adapts to them ex post facto. As for dynamic constraints, they work without any regularity over time. Their random character may cause irreversible or durable imbalances for societies that are not prepared for these kinds of events.
Using the approach of natural constraints in the geographical framework of the relationship between nature and society thus implies taking into account the plurality and relativity of their expressions in space and time. Within this perspective, it would be erroneous merely to equate the study of natural constraints with that of natural risks. As soon as their nature implies a reflection on the relationships linking the world of ideas in our societies to that of material realities, it becomes necessary to evaluate their role in the creation of myths,
Physical, natural constraints on the one hand, and socio-economic, mental or historical constraints on the other, each having their own rules, work according to different processes, and evolve at varying speeds. But separating them because their processes are of a different nature amounts to overlooking the fact that they share at least two common features: time and space.
Nature and society thus evolve within time-space increments at different speeds and according to processes of self-correlation in space and time. Both take part in organising, elaborating and building the structures of territories. All of these constraints may generate dysfunction, even to the point of territorial systemolysis. The way a territory functions is the outcome of the interplay of a field of constraints, the combined interactions of a set of natural, physical, social, economic, historical, and mental constraints. From a conceptual standpoint, all of these constraints are on the same footing within the system. In principle no single constraint is dominant, but neither is any one of them negligible. Each of them accounts for a part of the total picture of a territory, according to a variable percentage ranging from 0%+epsilon to 100%-epsilon.