Issues that remain
The improvements in the post-2020 GBF draft are laudable, and we believe
reflect an increasing understanding among CBD policy makers regarding
genetic diversity and its importance. However, the current wording
misses some elements, and further refinement of the text is critically
needed to retain key principles and ensure robust monitoring and
reporting, while avoiding perverse incentives and potential loopholes
(see Table 2).
Goal A currently includes maintenance of genetic diversity “within all
species” or “within wild and domesticated species.” Either phrasing
is suitable, as both emphasize that genetic diversity within all
species matters (note: the word “within” should be used).
The ambition remains insufficient at 95%, as highlighted by Frankham
(Frankham 2022), who showed
that essentially no genetic diversity (specifically, heterozygosity) can
be lost, e.g. 100% must be maintained. Still, a commitment to
percentage may be problematic for two reasons. First genetic diversity
can be assessed with numerous metrics (Ne, allelic richness,
heterozygosity, adaptive genetic variance) and each is lost at different
rates. Heterozygosity is the most common metric, but allelic richness
declines much faster. Second, regardless of the metric, a percentage is
hard to monitor temporally as only few thousand species globally have
any population genetic data (DNA data from individuals across geographic
space), and perhaps only a few dozen species globally have regular
temporal DNA assessments. Most countries simply cannot accurately report
a percentage of genetic diversity maintained.
The GBF may be better served by stating ‘maintain all within population
genetic diversity and maintain all distinct populations,’ or ‘maintain
sufficient genetic diversity within populations and maintain all
distinct populations.’ For most populations, ‘sufficient’ will refer to
no loss of current genetic diversity, or restored genetic diversity, and
this can easily be reported using indicators for an effective population
size of 500 to mitigate loss fom genetic drift. No loss is consistent
with CBD’s Mission (“To take urgent action across society… to
put biodiversity on a path to recovery by 2030 for the benefit of planet
and people” and Vision (“living in harmony with nature”), especially
as many species already suffered high genetic diversity loss
(DiBattista 2008;
Leigh et al. 2019; Exposito-Alonso et al. 2022). Ne ≥ 500 is important
for all populations within species regardless of past losses.
A final issue continues to be ambiguous wording. Depending on wording
retained, the Goal and Target might be confusing or contradictory. We
suggest that the terms ‘safeguarded’ and ‘maintained’ may cause
confusion and could be considered duplicative, unless it is made
clear that safeguarded means ‘protected’ (in seed banks and in
protected areas) and ‘maintained’ means ‘not lost .’ Two other similar
words are ‘genetic diversity’ and ‘adaptive potential’; both terms are
recommended by(Díaz et al. 2020;
Hoban et al. 2020). Geneticists typically interpret ‘genetic
diversity’ as genome-wide measures and ‘adaptive potential’ as diversity
in functional genes, or more generally as the extent to which
populations can evolve, which is a consequence of genetic diversity. The
two are not duplicative or fully interchangeable. Retaining the wording
‘adaptive potential’ also emphasizes the need for future adaptation of
populations to climate change, disease, and other challenges.