Taxonomy
Scientific Name
Crassothonna opima (Merxm.) B.Nord.
Higher Classification
Dicotyledons
Family
ASTERACEAE
Synonyms
Othonna opima Merxm.
National Status
Status and Criteria
Critically Endangered A2acd
Assessment Date
2022/08/19
Assessor(s)
D. Raimondo, P.C.V. Van Wyk, N.A. Helme & N.N. Mhlongo
Justification
This species has a limited distribution range within South Africa. The population has undergone a reduction of at least 95% due to the combined effects of mining and the ongoing droughts in the Northern Cape, which commenced in 2016 and persist at the time of this assessment. Although the species also occurs in the Sperrgebiet region of southern Namibia, the impacts of the drought have been equally severe. As a result, its national status is not downgraded, and it qualifies as Critically Endangered under criterion A.
Distribution
Endemism
Not endemic to South Africa
Provincial distribution
Northern Cape
Range
This species distribution stretches from the Richtersveld in the Northern Cape Province of South Africa into southern Namibia.
Habitat and Ecology
Major system
Terrestrial
Major habitats
Upper Annisvlakte Succulent Shrubland, Central Richtersveld Mountain Shrubland, Western Gariep Hills Desert, Western Gariep Lowland Desert, Kahams Mountain Desert, Noms Mountain Desert, Lower Gariep Alluvial Vegetation
Description
Plants grow on rocky slopes.
Threats
Anthropogenic climate change poses a long-term threat to this species. Since 2012, its entire range has experienced below-average rainfall. Predictions for future climate change indicate further increases in the annual average temperature, ranging between 1.4°C and 2.4°C by 2050. This will lead to unbearably hot temperatures and ongoing aridification throughout significant portions of the year (Van Wilgen et al., 2017). The species has suffered severely from a drought that began in 2016 and is still ongoing at the time of this assessment. Approximately 95% of this once common species is now dead and severely fragmented. Like other Crassothonnas in the region, they lack long-lived seedbanks, and plants have not flowered in many years. Once a subpopulation is lost, it is lost forever. In addition to the impacts of climate change, the species has already lost habitat to mining, and this loss will persist as mining operations expand their footprints. Mining has also resulted in the death of thousands of plants, and much more of the habitat will be lost in the coming years.
Population

The population consists of between 20-30 subpopulations across its range and between 10-15 locations within South Africa. A distinct difference exists between the northern Richtersveld and Sperrgebiet population and the southern Richtersveld populations, which are geographically divided. Whether this represents two variable subspecies or two entirely different species is a matter that requires further taxonomic assessment. Despite this distinction, the entire population has suffered a 95% decline due to the combined effects of the ongoing drought and mining activities.


Population trend
Decreasing
Assessment History
Taxon assessed
Status and Criteria
Citation/Red List version
Crassothonna opima (Merxm.) B.Nord.Least Concern 2015.1
Othonna opima Merxm.Least Concern Raimondo et al. (2009)
Bibliography

Nordenstam, B. 2012. Crassothonna B.Nord., a new African genus of succulent Compositae-Senecioneae. Compositae Newsletter 50:70-77.


Raimondo, D., von Staden, L., Foden, W., Victor, J.E., Helme, N.A., Turner, R.C., Kamundi, D.A. and Manyama, P.A. 2009. Red List of South African Plants. Strelitzia 25. South African National Biodiversity Institute, Pretoria.


Van Wilgen, N.J. and Herbst, M. 2017. Taking stock of parks in a changing world: The SANParks Global Environmental Change Assessment. SANParks, Cape Town.


Citation
Raimondo, D., Van Wyk, P.C.V., Helme, N.A. & Mhlongo, N.N. 2022. Crassothonna opima (Merxm.) B.Nord. National Assessment: Red List of South African Plants version . Accessed on 2024/06/14

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Distribution map


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