This indicator is based on the knowledge that populations that are small in size (effective population size (Ne) < 500) are highly susceptible to rapid loss of genetic diversity and are at high risk of extinction due to genetic threats. As shown in the figure, Ne 500 is widely recognized by scientists and conservation practitioners as a “sufficient” size to prevent loss of genetic diversity within populations (in this case, a statistic called ‘heterozygosity’) – Ne much higher than Ne 500 and genetic loss within populations is near zero. Much lower and genetic loss becomes rapid.

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