In 2019 South Africa became the first megadiverse country in the world to produce a national Red List Index (RLI) as part of its National Biodiversity Assessment. The RLI measures change in extinction risk status of species as a result of genuine changes, this excludes changes that result from taxonomic changes or the incorrect application of the Red List criteria. It is also a powerful tool to identify taxonomic groups that are in decline and need conservation interventions. It also indicates where conservation actions have resulted in improvements in the threat status of species over time.
The RLI index value ranges from zero to one. The lower the value, the faster the group of species is heading toward extinction and, the closer to one, more species are assessed as Least Concern. The South African RLI is based on Red List assessments that include mammals, reptiles, amphibians, birds, freshwater fish, butterflies, dragonflies and, a sample of 900 randomly selected plants. These groups have been assessed at least twice, and thus allows for the calculation of these trends.
Results from this analysis show that:
- Species confined to rivers and inland wetlands are declining more rapidly than those that occur in terrestrial ecosystems.
- Freshwater fishes and mammals making use of aquatic systems show the steepest decline. Conversely, some vertebrate groups do not show a strong decline.
- When comparing across all realms (terrestrial and freshwater), birds and reptiles are the least threatened of South Africa’s vertebrate taxa.
- While mammals show relatively high levels of overall threat, population declines for many species took place in the distant past (18th and 19th century) and the RLI has remained relatively stable over the last 15 years.
- Butterflies show a steep RLI decline that is concerning, suggesting there is a need to assess and monitor other groups of invertebrates, particularly given that many groups of invertebrates are thought to be in decline globally.
The trend for butterflies could be a warning sign that invertebrate communities may be heavily impacted. In response to this finding, SANBI has started engagements with invertebrate experts across South Africa to start monitoring programmes and to assess available data to prioritize Red List assessments, with a focus on pollinators.
Furthermore, based on the proportion of threatened species as well as the trends observed from the Red List for freshwater species, the South African National Biodiversity Institute has established freshwater fish and freshwater invertebrates expert groups who will work to improve our understanding of threats and where species are most impacted. They will provide the information needed to develop policy and decision support tools to reverse the declines to species.
The full suite of NBA products, which include a synthesis report, seven technical reports, datasets, maps, supplementary materials, and popular products, is accessible at http://nba.sanbi.org.za/