Projecting global biodiversity

Sala et al. [6] present scenarios for the status of biodiversity in 2100 for ten terrestrial biomes and the associated freshwater ecosystems.² These scenarios are based on:

• The five factors likely to have the largest impact on biodiversity changes over the next century:
  1. land use changes,

  2. the concentration of atmospheric CO$_2$,

  3. nitrogen deposition and acid rain,

  4. climate, and

  5. biotic exchanges, which they define as ``deliberate or accidental introduction of plants and animals to an ecosystem.''

• Expected changes in these factors, ``drivers'', in each biome between 2000 and 2100.

• The expected biodiversity impact of a unit change in each of those factors.

• Three possible ways in which the factors interact with one another in determining biodiversity change:
  1. No interaction: Each factor contributes independently to biodiversity change.

  2. Antagonistice interaction: Biodiversity change responds only to the factor that has the largest impact on it. The others have no effect.

  3. Synergistic interaction: Biodiversity change responds to the accumulated changes more than would be expected from an independent response to each factor by itself.