A gap exists between our ability to communicate the ideas of biodiversity change to the general public, in large part due to a shortcoming in a standard vocabulary to describe key, elementary, concepts.
Consider a simple example of biodiversity change: Plant diversity has increased on mountain summits in the Alps during the past century  because species formerly restricted to lower elevations have moved upslope, whereas incumbent populations have persisted. Is this increase in diversity permanent or transient? Should one expect some of these species, adventive or incumbent, to go extinct? Taken at face value, the message for the general public and policymakers could be that global warming will increase alpine biodiversity. If this is incorrect, how do researchers communicate the alternatives?
This work sets about formalizing and recording some of the key concepts necessary to explain these processes. I’ll add each of these as separate definition entries for indexing purposes.
Biodiversity accrual, Biodiversity balance, Biodiversity loss, Biodiversity deficit, Biodiversity surplus, Compositional turnover, Delayed extinction, Delayed immigration, Equilibrium biodiversity, Extinction debt, Extinction lag, Forcing event, Immigration credit, Immigration lag
you should be able to find the definition entry by clicking the Tag of the same name.
The paper goes on to clarify some of the conditions and events that lead to each of the above actions.
Figure 1 Jackson and Sax (2010)
In particular, that many of these actions happen over variable time intervals, related to the concept of reaching equilibrium in the system and the various interactions that can delay that result.
Some resulting questions:
- Can indicators of biodiversity surplus or deficit in existing ecosystems be developed?
- Can early-warning signs be identified for imminent biodiversity decline owing to extinction-debt payoff?
- How precisely can immigration credit and immigration rates be estimated?
- What risks and benefits accrue if managers attempt to intervene to, for example, foster immigration via managed relocation and or to prevent local extinction by taking extraordinary measures, such as modifying the physical environment to maintain previous conditions?
Jackson ST and Sax DF. Balancing biodiversity in a changing environment: extinction debt, immigration credit and species turnover. TREE. Volume 25, Issue 3, March 2010. Full text