Signals of consistent genetic diversity decline are not yet measurable in global meta-analysis

Genetic diversity within species must be conserved as the basis for evolutionary adaptive capacity. To inform new global conservation policy, Shaw et al.1 conducted a meta-analysis of temporal genetic diversity data for over 600 wild species spanning a median of 7 years, reporting significant overall diversity loss of effect size g = -0.1. My re-analysis translating this effect to percentage change finds no robust statistical support for consistent decline, with overall changes near zero--from -1% to +1% diversity change depending on the averaging method. When testing each species individually, roughly half increased and half decreased in diversity. While genetic diversity is expected to decline following population losses, evolutionary theory predicts such declines substantially lag behind population reductions, and thus should not be measurable on average at the timescales in Shaws data, except in dramatically collapsing species. However, conservation policy should not wait for consistently measurable genetic diversity loss--to avoid future lagging losses, we must protect populations now.