How to make a common species rare: A case against conservation complacency

A traditional focus in conservation biology has been on rare species as they are often those most at risk of decline or extinction. However, we argue in this paper that some kinds of currently common species also can be susceptible to decline. Those at particular risk are species that are specialized on widespread environmental conditions. Such specialization may make such species vulnerable to a range of drivers of environmental change, placing them at risk of significant decline or even local extinction. We illustrate this with a case study of the arboreal marsupial the Greater Glider (Petauroides volans) in south-eastern Australia. The Greater Glider was formerly common in two large-scale studies but in one it suffered rapid extinction (within a 3 year period) and in another it is declining at an annual rate of 8.8%. We therefore argue for more research to better predict those kinds of currently common species which might be at risk of future rapid decline or extinction. In addition, we suggest there will often be a need to take pro-active conservation and management action to reduce the number of potential environmental stressors on populations of common species to ensure they do not become uncommon or rare. We also argue that conserving common species will ensure the retention of their key ecological and functional roles in ecosystems. Finally, we believe there is a need to develop better monitoring programs that can detect changes in the population trajectories of common species, help identify the reasons for temporal changes in such populations, and underpin timely management interventions. Despite these good intentions, we acknowledge that in one of our own long-term investigations we: (1) failed to anticipate the extremely rapid decline (and likely local extinction) of the Greater Glider, (2) were unable to diagnose the reason/s underpinning the population collapse, and (3) nor were we able to instigate a timely intervention program of management to prevent this from occurring. The key lesson from this sobering result is that common species can sometimes be at risk of rapid decline and it is wise to avoid complacency in conservation.