Stability of Grazing Systems: An Application of Predator-Prey Graphs

In a now classical paper, Rosenzweig Maly 1969; McAllister, Le Brasseur Holling 1965). But herbivore ('predator')-plant ('prey') interaction is sufficiently similar in its general features to make the same approach useful. Some important modifications are necessary, on the basis of biological considerations, but some results are directly transferable between predator-prey and herbivore-plant systems. Grazing systems have some advantages as relatively simple test cases for general ecological theories: the number of species is limited (usually only one herbivore, in some cases one or a few plant species), environmental heterogeneity within a system is often low and movement of animals is controlled. There is a large and increasing number of observations and experiments on pasture and range systems in many parts of the world. On the other hand, grazing systems are one of the types of ecosystems which are of greatest importance to man; if theoretical ecology could contribute to their understanding and to the solution of their practical management problems, this would be a very useful contribution indeed.