International Encyclopedia of Systems and Cybernetics

The net of interconnections in an ecosystem between the resources and their users (microorganisms, vegetals and animals)

Practically in any ecosystem there is a multiplicity of resources (energetic, mineral, spatial) and users, most of them direct (or primary) users and various levels of indirect users. Many or these become in turn resources for the higher levels users, that must be considered as predators.

In a trophic net, the same resource can be used by different users and, conversely a specific user can use various types of resources.

The trophic net includes also wastes, that are generally recycled by some specialized users and are reincorporated as primary resources. The general motor of the net is energy, normally solar, in a direct or undirect way, but also sometimes geothermal.

The trophic net is in fact a complex network wherein some correlations are impossible or prohibited, and others possible in some ways and under some conditions.

It can be represented by graphs, more or less complex according to their aggregation or disaggregation levels.

Trophic nets are generally nonlineal. A vegetal or animal species can be eaten by different predators. Conversely the same predator may eat different preys.

This explains some failures in biological control of pests: An introduced species may very well switch to a prey different from the one it was supposed to feed on.

Also, the evolution of populations can turn chaotic if some instability threshold is crossed. In such a case also the global trophic net can be deeply- and sometimes, irreversibly- disturbed

Most trophic nets have been deeply altered by man, who pretends to be the global and universal user, generally without a good understanding of their local and/or general conditions of dynamic stability. As a result, crashes and collapses could become inevitable and quite disastrous.

The whole subject has been exhaustively researched by some ecologists, as for instance the Catalan R. MARGALEF (1982)

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