Biodiversity balance

Balancing biodiversity in a changing environment

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 [10] 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.

The terms:

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
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There are some monster crocs in the Zambezi river - up to 18 feet long. They can often be seen on the shores sunning themselves because they are ectothermic and rely on the sun to heat themselves before becoming active. These prehistoric reptiles have inhabited the earth for over 300 000 years and have remained an Apex Predator. Although dangerous - crocodiles in their habitat should not be seen as a threat but more for their important role in the river ecosystem to ensure that rivers are functioning and well-balanced. #crocodile #zambezi #wildlife #ecosystem #biodiversity #conservation #zambia #african #balance #carnivore #predator #prehistoric #reptile by jamessuter

Some key terms in biodiversity change

Biodiversity accrual

a net increase in the number of species following a forcing event.

Biodiversity balance

the net difference between immigration credit and extinction debt once equilibrium is achieved.

Biodiversity loss

a net decrease in the number of species following a forcing event.

Biodiversity deficit

a transient decrease in the number of species following a forcing event.

Biodiversity surplus

a transient increase in the number of species following a forcing event.

Compositional turnover

community change, particularly species replacements, that occurs following a forcing event.

Delayed extinction

the general phenomenon in which one or more extinctions that are caused by a specific event do not coincide precisely with that event, but instead follow it by some significant amount of time, which can range from a single generation (e.g. delayed mortality of a long-lived incumbent that fails to either reproduce or recruit successfully) to multiple generations (whereby populations persist for multiple generations, usually in diminishing numbers).

Delayed immigration

the general phenomenon in which one or more immigrations that are caused by a specific event do not coincide precisely with that event, but instead follow it by some significant amount of time.

Equilibrium biodiversity

the number of species in a system once it has attained equilibrium.

Extinction debt

the number of species committed to eventual extinction following a forcing event.

Extinction lag

the time elapsed between an extinction-committing forcing event and the final disappearance of a species.

Forcing event

any event that causes the extinction or immigration of one or more populations or species, whether immediate or delayed.

Immigration credit

the number of species committed to eventual immigration following a forcing event.

Immigration lag

the time elapsed between an immigration-committing forcing event and the establishment of an immigrating species. 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