Table 1.

How several components of terrestrial biodiversity may have changed, averaged across the globe

MetricOverall trend*Example/processRef(s).
Genetic diversity: variation among populations within speciesDecliningLoss of genetically distinct populations and races20
Local diversity: no. of species per unit area, within habitatsStableChanges in local plant diversity show no overall pattern of global increase or decrease3
Local diversity: no. of species per unit area after conversion to human-dominated land useOften decliningLow diversity in agricultural land compared with natural vegetation, such as conversion of rainforest to oil palm plantation10
Regional diversity: no. of species per country, state or islandIncreasingMore nonnative introduced species establish than native species die out6
Global diversity: no. of species on EarthDecliningHigh documented extinction rates5 and 21
  • * There are often exceptions to the overall trend.