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Magaliesberg Aloe

Taxonomy
Scientific Name
Aloe peglerae Schönland
Higher Classification
Monocotyledons
Family
ASPHODELACEAE
Common Names
Bergaalwyn (a), Grootaalwyn (a), Magaliesberg Aloe (e), Red-hot Poker (e)
National Status
Status and Criteria
Critically Endangered A4abd
Assessment Date
2016/09/13
Assessor(s)
M.F. Pfab, L. von Staden & N. Hahn
Justification
Aloe peglerae is a localized, range restricted species (EOO 3415 km²). It is known from two extensive subpopulations and two smaller ones. Field monitoring of selected sites indicated a 43% population reduction over 10 years. Should this trend continue, which is likely as the illegal removal of plants from the wild is very difficult to control, it is estimated that the overall population reduction will exceed 80% within three generations, which includes the past 10 years as well as the next 60 years, representing two generations into the future.
Distribution
Endemism
South African endemic
Provincial distribution
Gauteng, North West
Range
Magaliesberg and Witwatersberg.
Habitat and Ecology
Major system
Terrestrial
Major habitats
Gold Reef Mountain Bushveld, Waterberg-Magaliesberg Summit Sourveld, Rand Highveld Grassland
Description
Grassland, in shallow, gravely quartzitic soils on rocky, north-facing slopes or summits of ridges.
Threats
The most severe threat to Aloe peglerae is illegal collection of mature individuals from the wild. As a long-lived, slow growing species, even very low levels of harvesting is unsustainable. Most illegal collection is thought to be incidental and opportunistic, making it very hard to control (Pfab and Scholes 2004). Monitoring indicates that this threat is ongoing across the population, and is not just confined to areas with public access (Phama et al. 2014). High levels of seed harvesting for the horticultural trade is also likely to have a long term impact on the viability of this species (Pfab and Scholes 2004), particularly in that it limits the population's ability to recover from ongoing, rapid decline. Habitat loss to urban expansion and other land development is a threat around Pretoria, Krugersdorp and Hartbeespoort. Most of this species' habitat is however protected in formally protected areas as well as many private nature reserves, and development is therefore a minor threat, affecting only a small proportion of the population.
Population

Aloe peglerae has a limited distribution range, and is localized to quartzitic ridges in northern Gauteng and adjacent areas in North West Province. Within this area, the species is still relatively abundant, but local declines due to illegal removal of plants from the wild is concerning. There are four known subpopulations, one recently discovered during a survey of suitable habitat in North West (Hahn 2013). The two largest subpopulations occur along the summit ridges of the Magaliesberg and Witwatersberg between Rustenburg and Pretoria, each consisting of more than 10 000 mature individuals. Two smaller subpopulations of around 1000-2000 mature individuals occur near Krugersdorp and in the Koster district. Field observations indicate that the species has become scarce or extirpated in places accessible to the public (Pfab and Scholes 2004). At least 200 plants were recorded in the Kgaswane Nature Reserve near Rustenburg in the 1980s (Hahn 2013), but fewer than 10 plants could be found in a 1999 survey (M.F. Pfab pers. comm. 2005), and no plants could be found during the most recent field surveys (2008-2013, Hahn 2013). Demographic monitoring over a period of 19 years indicate that Aloe peglerae is slow growing, long-lived and recruitment is very low (Scholes 1998). Based on this data, the generation length for the species is estimated to be 30-40 years. Due to these demographics, Aloe peglerae is extremely sensitive to illegal wild collecting of plants. A population viability model indicate that the removal of only one plant per year in subpopulations consisting of 1000 mature individuals or less causes a high probability of local extinction within three generations (Pfab and Scholes 2004). For larger subpopulations, wild harvesting is sustainable only at extremely low harvesting levels of 0.12% or less per annum, which in a subpopulation of 10 000 mature individuals equates to 12 plants per annum. With the wild population of Aloe peglerae estimated to be around 70 000 mature individuals in 2004 (Pfab and Scholes 2004), wild harvesting of more than 70-80 mature individuals per annum is estimated to lead to ongoing population decline. Repeat sampling of nine selected sites across the Magaliesberg in 1999 and 2009-2010 indicates ongoing population decline at seven of the nine sites, with an overall population reduction of 43% over this 10 year period (Phama et al. 2014). Significant declines were not just limited to publicly accessible land, but also occurred on privately owned sites. Should this trend continue, population reduction would exceed 80% within three generations.


Population trend
Decreasing
Citation
Pfab, M.F., von Staden, L. & Hahn, N. 2016. Aloe peglerae Schönland. National Assessment: Red List of South African Plants version 2017.1. Accessed on 2019/12/11

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