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+---
+layout: default
+title: Ne 500 indicator
+parent: Theoretical background
+---
+
+# Ne 500 indicator
+
+The Ne 500 indicator is based on comparing the effective population size of each population Ne to a critical threshold (e.g. Ne = 500).  For many species, it is sufficient and appropriate to use the census size Nc (the number of living adults) as a proxy for Ne, and a threshold of Nc = 5000 mature individuals.  Below this threshold, a population rapidly loses genetic diversity, can become inbred, and starts to lose ability to adapt to environmental change.
+
+
+The primary undertaking is to gather the data on populations for each species.  This is a challenge because there is no global, standard database of population census size (The Living Planet Index for example does not measure full population census, and not all Red List species have census size for each population).  But the census size of many populations of many species is available in different reports and databases, in more or less easy ways to extract.  This documentation will explain how to gather and use the necessary data, from diverse sources, in a standard way.
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 # Theoretical background
+{: .no_toc }
+
+This section has a brief theoretical background on the genetic diversity indicators.
 
-This section has a brief theoretical background on:
 
-* Ne 500 indicator
-* Populations maintained indicator
-* What is a population