Comparing and contrasting threat assessments of plant species at the global and sub‑global level

ABSTRACT

Evidence-based assessments of extinction risk are established tools used to inform the
conservation of plant species, and form the basis of key targets within the framework of the
Global Strategy for Plant Conservation (GSPC). An overall picture of plants threat assessments
is challenging due to the use of a variety of methodologies and range in scope from global to
subnational. In this study, we quantify the state of progress in assessing the extinction risk of all
land plants, determine the key geographic and taxonomic gaps with respect to our understanding
of plant extinction risk, and evaluate the impact of different sources and methodologies on the
utility of plant assessments. To this end, we have analyzed a cleaned dataset compiled from
IUCN Red List of threatened Species and Regional Red Lists. We reveal that there are
assessments available for 89,810 distinct species or 25% of all accepted land plant species.
However unlike with other major organismal lineages the bulk of the plant species assessments
are derived from Regional Red Lists, and not the global IUCN Red List. We demonstrate that
this bias towards regional assessments results in distinct taxonomic and geographic strengths and
weaknesses, and we identify substantial taxonomic and geographic gaps in the assessment
coverage. With species that have been assessed in common at both global and regional levels, we
explore the implications of deriving threat assessments from different sources. We find that half
of global and regional assessments do not agree on the exact category of extinction risk for a
species. As expected, regional assessments tend to assign a higher risk of extinction, however
worryingly regional assessments underestimate extinction risk with almost equal frequency. We
conclude with recommended interventions, but support the suggestion that all threat assessments

3 should be pooled to provide a more data for GSPC targets.