Abstrait

Global biodiversity: Extinctions and originations

John C.Briggs

Most claims of global biodiversity loss,while they appear to be reasonable, suffer from the problem of scale. Reliance is placed on data from islands and other restricted localities and extrapolated to the size of the entire globe. It is possible to avoid the scale effect by relying on direct information about extinctions, rather than indirect approximations as indicated by habitat decline, the species-area curve, and invasive species. Aside from isolated islands or space-restricted freshwater habitats, there is a lack of evidence indicating an abnormal loss of species diversity on the EarthÂ’s continents and oceans. Instead, speciation apparently continues to provide the world with gains in biodiversity, leaving little justification for claims of unusual global losses. The worldÂ’s major conservation problem is not the loss of species, it is the plight of thousands of threatened populations, remnants of larger ones that have been over-exploited or restricted by loss of habitat. This means that our conservation attention needs to be shifted from alarm over unsubstantiated global biodiversity loss, to the current problem of the rescue of small populations that are under threat.