Complex or Interactive? New Perspectives in Ecological Modeling

Michael Hauhs, Ecological Modelling, University of Bayreuth

Modelling offers two perspectives at environmental systems and ecosystems. The first one originated from Newtonian physics and is based on the theory of dynamic systems. Its central physical notion is that of state; mathematically it represents an algebra. This first approach is widespread among environmental modellers and is sometimes even identified with the scientific method as such. The second (new) approach has recently been derived within computer science. Its central notions are behaviour and interaction, which can be implemented with today’s computers. Mathematically such models represent a coalgebra. The notion of interactive computation extends the physical notion of functions into the realm of decision making, e.g. in a growing organism. Difficulties and limits of ecological modelling have often been described as resulting from the high complexity of these systems. Such an interpretation can now be challenged with the view, that principle limits may be linked with the interactive nature of Life rather than with its complexity. The alternate perspectives will be illustrated in an example from hydrology.