Danube Rivers Morphology and Revitalization - DANUBEPARKS

Figure 4 – General model of ecosystem performance. An ecosystem or habitat thatis in rudimentary condition with low functioning develops into a system with optimalstructure and functioning. Development can take several pathways, and can oscillatebetween system states (Thom R.M, 2004).Figure 4 also indicates that a system may oscillate between states. This canbe caused by stochastic processes such as human or natural disturbances, as wellas stochastic climate related forcing. This dynamic may be more pronounced in somesystem types than in others. It is important to recognize that the system can movebetween different structural and functional states and still maintain its long-termintegrity.If stressors are removed, the natural recovery (passive restoration) ofecosystems will tend to take place regardless of human intervention, but this maytake a very long time— decades or centuries. Active restoration essentially meansthat humans act beyond stress removal to reduce the period of time required toimprove ecosystem conditions, through a combination of physical intervention andnatural recovery. At the desirable ecosystem condition, the system is fully functional,has an optimal structure, is resilient to disturbances, and is self-maintaining.However, the definition of “optimal” must be made with care and with relevance to thesystem under investigation. In the case presented here, it is assumed that optimalconditions are met with a natural climax community that, because of its persistence,is resistant and maintains itself through the ability to buffer changes. The term“optimal” implies a human value, and the optimal state represents what humans (i.e.,restoration planners) view as the “best” condition for the system.33