The role of restoration in the management of alien plants invasions
Invasions can reduce ecosystem resilience – that is to say the magnitude of disturbance that a system can absorb before it changes to alternative (stable) state. If resilience is reduced below a certain threshold, the system will change to an alternative state. Alternative ecosystems can shift (often very abruptly) between two or more states and may have dynamics that are fundamentally different from those of pristine ecosystems. The trajectory to recovery will therefore differ in unpredictable ways from a pristine state to a degraded state. If the invaded ecosystem reaches a certain degree of degradation, it might shift to a hybrid or even to a novel ecosystem state; depending on the interactions between biotic and abiotic changes triggered by invasive species.
Traditional restoration practices have focused on re-establishing historical biotic and abiotic conditions. However, in view of the significant changes caused by invasive species, new approaches recognize the existence of alternative (stable or transient) ecosystem states.
The author highlights the growing challenges in restoring ecosystems affected by invasive alien plants, to illustrate a framework for restoring ecosystems degraded by invasions adopting concepts of alternative states, thresholds and novel ecosystems, and to identify new questions and research needs for the development of a general framework for restoring ecosystems affected by alien plant invasions.
Sources
Gaetner M, Holmes P M, Richardson D (2011) Managing alien plant invasions: the role of restoration – Insights from South Africa. In Brunel S, Uludag A, Fernandez-Galiano E, Brundu G (Eds.) Proceedings of the 2nd International Workshop on Invasive Plants in the Mediterranean Type Regions of the World, 2010-08-02/06, Trabzon, Turkey pp. 256- 266.