Swartland Sugarbush

Taxonomy
Scientific Name
Protea odorata Thunb.
Higher Classification
Dicotyledons
Family
PROTEACEAE
Common Names
Swartland Sugarbush (e)
National Status
Status and Criteria
Critically Endangered A2ac; B1ab(iii)+2ab(iii); C2a(ii); D
Assessment Date
2022/02/07
Assessor(s)
A.G. Rebelo, D. Raimondo, L. von Staden, C. Dorse, J. van der Merwe & M. Nndanduleni
Justification
Protea odorata is a species endemic to the lowland Fynbos of Swartland region in South Africa. It has lost 86% of its habitat to crop cultivation, urban development and habitat degradation as a result of invasive alien plant spread, overgrazing by livestock and inappropriate fire regimes. This species is now on the brink of extinction, known only from one subpopulation with an extent of occurrence (EOO) and area of occupancy (AOO) of 4 km². The population has declined from four subpopulations totalling 1090 plants in 1975 to three mature individuals from one subpopulation in early 2020 (generation length is 15-20 years). As a serotinous species dependent on fire for recruitment, this species' ongoing survival is dependent on correct fire return intervals and being burnt in the correct session. The last remaining habitat for the species was burnt in February 2020 in a controlled burn organized by conservation authorities. Seed was augmented from the Millennium Seedbank collections. It is unknown if the plants will recruit and survive to maturity. If recruitment is successful fewer than 50 mature plants are likely to recruit as no more than 30 plants have been recorded at this site over the past four fire cycles and past experiments with seed augmentation have yielded low recruitment success. This species is therefore listed as Critically Endangered under criteria A, B, C and D.
Distribution
Endemism
South African endemic
Provincial distribution
Western Cape
Range
This species is known from the Swartland region of the Western Cape in South Africa, historically occurring between Kalbaskraal to Klapmuts, currently extant only at Joostenbergkloof.
Habitat and Ecology
Major system
Terrestrial
Major habitats
Swartland Shale Renosterveld
Description
It grows in slightly saline gravelly and sandy flats at low altitudes recorded from between 120-150 m.a.s.l. Mature individuals are killed by fires, and only seeds survive. Wind-dispersed seeds are stored in fire-resistant inflorescences, and released after fires. It is pollinated by insects. Plants require seven to 12 years to set sufficient seed.
Threats
A total of 86% of this species' habitat has been lost mainly to crop cultivation (cereals and pasture) as well as to urban development. Since the 1950s it has remained only in remnant fragments of lowland Fynbos. As a serotinous species that requires at least 7 years before sufficient seed is set, it is highly susceptible to incorrect fire regimes and there has been a significant decline in the remaining numbers of mature individuals as a result of incorrect fire management. The only subpopulation remaining since 2000 occurs on private land where it has been impacted by browsing by livestock and degradation of its habitat due to invasive alien plant species. The three subpopulations lost between 1980 and 2000 were as a combined result of invasive alien plants, livestock overgrazing and inappropriate fire regimes. One subpopulation was lost in 1954 due to roadworks.
Population

Since 1975, the overall population has declined from an estimated 1090 plants to three plants in early 2020 prior to a burn that took place in February 2020. Five subpopulations of this species remained in 1950, below the declines to each of these subpopulations is detailed: Riverlands Nature Reserve: A subpopulation of 20 plants was impacted between 1979 and 1982 by fires, sheep grazing and Acacia shading (Hall 1982). Some three plants existed in 1989. Ad hoc reintroduction of 10 plants into Riverlands failed in 1990 (Hilton-Taylor 1996). In 1996 two old skeletons of P. odorata from the previous fire cycle were seen, but no live plants. Groenrivier: Numbering over 1000 plants in the 1970s, by 1982 the largest subpopulation had 410 plants in 3 ha, but was severely grazed and trampled and only contained 50 seed heads (Hall 1982). About 600 plants occurred in 1986. In 1987 the stands burned, leaving less than 100 plants. In 1989 after another fire there were no plants left. Kalbaskraal: This subpopulation of 110 plants in 1968 was down to one plant in 1982 (Hall 1982), and 17 plants in 1989: two plants in the western section (established from 500 seeds sown after a 1977 fire), and 15 in the eastern section (Pool et al. 1992). One possible seedling was seen in 1996. It could not be found in 1997. Another subpopulation of three plants in the Kalbaskraal village was destroyed in 1983 by garbage dumping. N1 at Klapmuts: What appears from herbarium records to have been an 8 km long subpopulation was destroyed by roadworks for the N1 during 1954 (Jardine 1999). It has not been recorded there since then. Joostenbergkloof: Some six plants in 1975, a single plant occurred in 1986, but a number of seedlings established after a fire in 1987. In 1996 the farmer bush cut the area and planted oats, killing the four plant patch. Some three skeletons were recovered (one plant was still alive although flattened) and their still-closed seed heads scattered around, some 20 seed heads (about 25%) were taken to Kirstenbosch Gardens for ex situ conservation. In 1999, 34 plants (Forshaw 1999) were known. In 2002 it was noted that all the seed heads had been chewed off by cattle. The area was fenced in 2003 by the farmer, but four plants were left outside the fence, two of which are being trampled in a cattle path around the enclosure. Attempts to buy the land have stalled on land prices. Several proposals to develop vineyards, houses, and a golfing estate on the site have been turned down. The population has declined since 1999 to three plants in February 2020 when the site was burned and only one plant had seed heads with an estimated five viable seeds. The millennium seedbank project has saved seed of this highly threatened species, collected from stock beds of plants planted from the subpopulations described above. A total of 1900 seeds were sown prior to the winter rains in April 2020. It is hoped that some of these seeds will germinate and this species will continue to survive. Extensive ex situ propagation of this species has been undertaken by horticulturalists based at Kirstenbosch Botanical Gardens and also by the City of Cape Town's Conservation Branch. A living gene bank of approximately 20 individuals is maintained by ongoing germination of seeds and the planting of seedlings into stock beds. There are very high levels of mortality of seedlings and only a handful of individuals survive with each planting effort. Spreading of 2000 seeds into burn areas of suitable habitat at Joostenbergkloof in 2018 was unsuccessful. Following the burning of the last remaining plants and unburnt habitat in February 2020, a further 15 900 seeds were scattered prior to the first winter rains in April 2020 and a further 8300 seeds will be spread during the course of 2020 winter in an attempt to improve recruitment success. The site where the last remaining subpopulation occurs is privately owned but is in the process of being purchased by WWF for conservation.


Population trend
Decreasing
Assessment History
Taxon assessed
Status and Criteria
Citation/Red List version
Protea odorata Thunb.CR A2c; B1ab(i,ii,iii,v)c(iv)+2ab(i,ii,iii,v)c(iv); C1+2a(i,ii); DRaimondo et al. (2009)
Protea odorata Thunb.Endangered Hilton-Taylor (1996)
Protea odorata Thunb.Endangered Hall et al. (1980)
Bibliography

Forshaw, N. 1999. Pr odorata: sensation at Joostenberg. Protea Atlas Newsletter 42:4.


Goldblatt, P. and Manning, J.C. 2000. Cape Plants: A conspectus of the Cape Flora of South Africa. Strelitzia 9. National Botanical Institute, Cape Town.


Hall, A.V. 1982. Rare plants Gazette No 1. February 1982. Bolus Herbarium, University of Cape Town.


Hall, A.V., De Winter, M., De Winter, B. and Van Oosterhout, S.A.M. 1980. Threatened plants of southern Africa. South African National Scienctific Programmes Report 45. CSIR, Pretoria.


Hilton-Taylor, C. 1996. Red data list of southern African plants. Strelitzia 4. South African National Botanical Institute, Pretoria.


Jardine, I. 1999. Rediscovery of Protea odorata. Protea Atlas Newsletter 43:12.


Pool, R., Smuts, L.M., East, P.R.J. and Burgers, C.J. 1992. Rare and threatened Proteaceae reports. Vol. 1. Cape Nature Conservation Unpublished Internal Report 9.


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.


Rebelo, T. 2001. Sasol Proteas: A field guide to the proteas of southern Africa. (2nd ed.). Fernwood Press, Vlaeberg, Cape Town.


Citation
Rebelo, A.G., Raimondo, D., von Staden, L., Dorse, C., van der Merwe, J. & Nndanduleni, M. 2022. Protea odorata Thunb. National Assessment: Red List of South African Plants version . Accessed on 2024/04/17

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