species-area relationship (SAR)

The relationship between the size of an area and the number of species it contains can be used to predict extinction rates due to habitat loss. The relationship implies that halving an area reduces the number of species present by about 10%. The SAR has been used to estimate the extinction risk of global warming. Using mid-range projections about 25% of species will be extinct or heading for extinction by 2050, or about 40% in a ‘business as usual’ projection.

This definition is abridged from A – Z of tree terms: A companion to British arboriculture.
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