Viewing invasive species removal in a whole-ecosystem context.

Zavaleta, ES; Hobbs, RJ; Mooney, HA. 2001. TRENDS IN ECOLOGY & EVOLUTION 16 (8): 454-459.

This paper is mostly geared toward restoration practitioners who are designing invasive species eradication projects. The authors highlighted the possibility of creating secondary impacts on and/or unexpected changes in the ecology of a place after eradication of an invasive plant or animal species. Examples of secondary impacts included trophic cascades in a multiple invader system in which the eradication of one invader may be to the unintended advantage of a different invader in the same landscape. A trophic cascade influencing secondary impacts could be the unintended increase of an invasive herbivore pressure by releasing the invasive them from the pressure of an invasive predator after eradicating the predator. The paper described several possible permutations of cascades at various trophic levels. The authors also included other unintended impacts of invasive eradication such as the removal of habitats niches which natives may have become dependent on if an invasive had been long established.

The paper was a very good overview of how “successful” invasive eradication projects may impact a system in sometimes unexpected and negative ways. In this way it served the purpose of illuminating the need for pre- and post assessment of sites for better identification of possible feedback loops and for adaptive management purposes. However, although the authors gave real world examples to illustrate different secondary impacts the paper discussed, they did not give details on time frames of monitoring or give specific recommendations that might help a practitioner design better projects. The take home message was purely that future projects should combine eradication methods with larger ecological principles and goals. If you don’t know much about eradication projects and possible secondary impacts this paper would be a good overview.