Response to Strubbe et al. (2011): Impact scoring of invasive birds is justified

摘要

In their recent paper, Strubbe et al. (2011) raise concern regarding the scoring of impact and ranking of alien birds in Europe performed by Kumschick and Nentwig (2010). Their major points are that we might have overestimated impacts of alien birds in Europe in the respective study, and therefore came to the “premature” conclusion that some birds should be considered for eradication. Strubbe et al. re-scored the literature provided and reached lower impact scores, even though their order of the ranking was the same as in our study. This actually speaks for the robustness of our impact scoring system. They also statistically compare their scores with the scores reached in our study, and they are either barely (p = 0.042 for environmental) or not (p = 0.062 for economic impact) significantly different; still they talk about “considerable differences” between the two scoring procedures, which in our understanding is not the case. Furthermore, Strubbe et al. compared these scores with the impact scores for mammals provided by Nentwig et al. (2010), without re-scoring the impacts for mammals however. For reasons of consistency, they should rather have re-scored all the species considered for their analyses and statements. Furthermore, since both the bird and mammal study were mainly performed by the same people, it is likely that both were scored according to similar criteria. So it might be naive to assume that bird impacts were scored too high and therefore inaccurate and mammal impacts on the other hand were scored in the sense of Strubbe et al., so rather low.