This paper sets out to review what the term “extinction debt” means, what kind of support do the exisitng empirical studies provide for the term, and what are the main drivers that give rise to extinction debt. While extinction debt clearly has broad implications for conservation, authors emphasize how hard it is to detect extinction debt in natural communities and call for more studies to improve our understanding of the phenomenon.

The authors (quite a group of them!) have managed to pull together a good compilation of studies looking into potential cases of extinction debt (Table 1 in the article). However, the article does not offer any particularly new insights to the matter of extinction debt. Novelty factor is not necessarily an issue for a review article, but good organization and coherence are and these were partly missing from the article. The text is very heterogeneous both in language used and content, which might be a result from a large number of authors. For example, authors give out examples from the literature, but do not compare the studies at all or discuss the potential implications very widely. Why did some studies find evidence for exitinction debt while others did not? Is it because the community studies has no extinction debt to pay or because the methodology used could not detect it? Authors underline the importance of being able to quantify extinction debt in order to “counteract future biodiversity loss by targeted habitat restoration and conservation actions”, but give only vague instructions on how conservation actions should be directed in the face of extinction debt. Should the conservation priority be set on species with long or short delay before looming extinction?

This review provides a good overview on the experimental studies looking into extinction debt in natural populations. Unfortunately, the final synthesis does not deliver as much as it potentially could. The text is somewhat inconsistent and a lot of implicit conclusions are left for the reader to make. The article concludes in demanding a lot more experiments, monitoring and general awarness on extinction debt, but gives very few actual recommendations for real-life conservation actions.

Final conlusion: good source for references, but the actual review-part leaves something to be desired.

Link to the paper:

Kuussaari, M., Bommarco, R., Heikkinen, R.K., Helm, A., Krauss, J., Lindborg, R., Öckinger, E., Pärtel, M., Pino, J., Rodà, F., Stefanescu, C., Teder, T., Zobel, M., Steffan-Dewenter, I., 2009. Extinction debt: a challenge for biodiversity conservation. Trends. Ecol. Evol. In Press, Corrected Proof.
doi:10.1016/j.tree.2009.04.011