Taxonomy
Scientific Name
Conophytum calculus (A.Berger) N.E.Br. subsp. calculus
Higher Classification
Dicotyledons
Family
AIZOACEAE
Synonyms
Conophytum calculus (A.Berger) N.E.Br. var. komkansicum (L.Bolus) Rawé, Conophytum komkansicum L.Bolus, Mesembryanthemum calculus A.Berger
National Status
Status and Criteria
Critically Endangered A4d
Assessment Date
2021/11/16
Assessor(s)
A.J. Young, P.G. Desmet, I. Ebrahim, D. Guo, A. Harrower, L. Jabar, L. Knoetze, C. Rodgerson, P.C.V. Van Wyk & N.N. Mhlongo
Justification
This succulent is endemic to the Western Cape province of South Africa with an extent of occurrence (EOO) of 2,629 km² and area of occupancy (AOO) of 156 km². The population is experiencing substantial decline due to the illegal ornamental succulent plant trade, with collection likely to increase as there has been a dramatic increase in the number of species and volume of plants targeted since 2019. The continued threat of illegal collection is therefore regarded as very high for this particular taxon and a decline of up to 90% of the population is likely within the next ten years. Climate change is also impacting the population although there is uncertainty of the response given the expected resilience of this taxon. It therefore qualifies as Critically Endangered under criterion A4.
Distribution
Endemism
South African endemic
Provincial distribution
Western Cape
Range
This taxon is endemic to a small part of the Western Cape province of South Africa.
Habitat and Ecology
Major system
Terrestrial
Major habitats
Knersvlakte Quartz Vygieveld, Southern Namaqualand Quartzite Klipkoppe Shrubland, Namaqualand Riviere
Description
It is endemic to the Knersvlakte bioregion of the Succulent Karoo biome. Plants are found on areas of quartz stones and pebbles with the plants usually fully exposed to the sun. The plants experience sporadic winter rainfall. This taxon has a generation length of 30 years. It is expected to be sensitive to the impacts of climate change as it does not disperse and while adapted to arid conditions, is dependent on limited seasonal rainfall. Species in the genus are sensitive to long periods of drought. Drought related mortality has been observed for other closely related taxa within the genus.
Threats
It is currently threatened by illegal collection for the international trade in ornamental succulents. This is likely to increase in future as there has been a dramatic increase in the number of species and volume of plants targeted since 2019. Anthropogenic climate change is a long-term threat to this taxon. Climate models for the likely emission scenarios where emissions stay at present day levels (RCP 2.6) (Hausfather and Peters 2020) and worst case scenarios where emissions continue to increase during the 21st century (RCP 8.5) indicate that there will be a loss of suitable bioclimatic envelope of between 40% and 85% by 2080. However, as this taxon possesses certain morphological traits likely to afford resilience to xerophytic conditions and is found across several vegetation units it is expected to have a level of resilience to climate change and the expected population loss is reduced by 20% to 20%. Species in this genus have limited dispersal ability and migration to suitable habitats elsewhere is regarded as highly unlikely.
Population

There is no formal estimate of population size for this taxon, but is estimated to be in excess of 20,000 mature individuals. The population is declining as a result of illegal collection of wild specimens to supply the ornamental succulent plant trade. This taxon has been highly sought after by collectors with several thousand plants removed illegally since 2019. A total of 11,600 plants have been confiscated from plant poachers with many others likely not to have been intercepted and to have found their way to China.


Population trend
Decreasing
Assessment History
Taxon assessed
Status and Criteria
Citation/Red List version
Conophytum calculus (A.Berger) N.E.Br. subsp. calculus VU A4bd2020.1
Conophytum calculus (A.Berger) N.E.Br. subsp. calculus Least Concern Raimondo et al. (2009)
Bibliography

Hammer, S. 2002. Dumpling and his wife: New view of the genus Conophytum. EAE Creative Colour, Norwich.


Hammer, S.A. 1993. The genus Conophytum: A conograph. Succulent Plant Publications, Pretoria.


Hausfather, Z. and Peters, G.P. 2020. Emissions - the 'business as usual' story is misleading. Nature 577(618-620).


Citation
Young, A.J., Desmet, P.G., Ebrahim, I., Guo, D., Harrower, A., Jabar, L., Knoetze, L., Rodgerson, C., Van Wyk, P.C.V. & Mhlongo, N.N. 2021. Conophytum calculus (A.Berger) N.E.Br. subsp. calculus. National Assessment: Red List of South African Plants version . Accessed on 2024/07/14

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Distribution map

© A.J. Young


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