I’d like to recommend the following paper:
Inger R, Gregory R, Duffy JP, Stott I, Voříšek P, Gaston KJ (2014) Common European birds are declining rapidly while less abundant species’ numbers are rising. Ecol Lett 2014 Nov 2, PMID: 25363472 DOI: 10.1111/ele.12387
This paper draws on the compilation of long-term data for European birds. It highlights that common species are declining, while rare species are increasing. This, in turn, raises doubts about conservation practices that are primarily focusing on the local scale, for example via creating (small) protected areas. Inger et al. imply that a broader-scale focus is needed for conservation, which needs to explicitly recognise entire landscapes. Especially from the perspective of ecosystem functioning (and ecosystem services), a decline of the most common species is particularly concerning.
This is an important paper that provides a strong empirical argument for why conservation should not target only species that are already rare.