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Aloe helenae 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Liliopsida Liliales Aloaceae

Scientific Name: Aloe helenae
Species Authority: Danguy

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(i,ii,iii,v)+2ab(i,ii,iii,v); C2a(i); D ver 3.1
Year Published: 2016
Date Assessed: 2016-04-12
Assessor(s): Rakotoarisoa, S.E.
Reviewer(s): Letsara, R, Rabarison, H., Rabehevitra, D., Jeannoda, V. & Hilton-Taylor, C.
Contributor(s): Rakotonasolo, F. & Ralimanana, H.
Facilitator/Compiler(s): Bachman, S.
Justification:

Aloe helenae has a very restricted geographic range around Amboasary Sud and Taolagnaro (Fort-Dauphin) districts in southern Madagascar. All available collections were made more than 70 years ago except one which was made in 1993. As a result of more recent searches from 2004 onwards, observations have been made for almost all sites except those located in Ivondro (north of Taolagnaro) and those around Lake Anony. These observations reveal the presence of the species at each site, but with very low numbers of individuals. Although the extent of occurrence (EOO) which is 2,991 km2 and the area of occupancy (AOO) which is 72-631 km2 do not meet the thresholds for Critically Endangered, they are small enough to meet the thresholds for Endangered, and are both reducing in size. The main threat to the species is the destruction of its habitat by land conversion for agricultural and mining purposes. Collection of living plants in the wild is reported and even leaves are used locally for medicinal purposes. However, this appears to be small scale, and does not impact the survival of the species. Aloe helenae is only recorded from one protected area. Seeds are banked at the Millennium Seed Bank, UK and at the Silo National des Graines Forestières, Madagascar. There are several living collections at the botanic garden in Antananarivo (Parc Botanique et Zoologique de Tsimabazaza), and a total of 21 collections are known from botanic gardens worldwide (BGCI Plant Search). Further research should be focused on visiting those sites where Aloe helenae  has not seen for up to 70 years to confirm whether the species is extant in those areas or not.

Previously published Red List assessments:

Geographic Range [top]

Range Description:

Aloe helenae is restricted to southern Madagascar in Taolagnaro region (Vinanibe, Lac Anony, Ivondro, Ranopiso, Ebobaky, Lokaro, Evatraha, Petriky), Ambovombe-Androy and Amboasary-Sud (Lake Anony, Behara, Amboasary-Sud). One subpopulation occurs in Petriky Protected Area. The area of occupancy (AOO) was estimated to be 72 km2 by using the recommended 2 x 2 km grid over all known extant localities. The area of suitable habitat was used to infer a plausible maximum area of occupancy (AOO) value, which was calculated to be 631 km2. The extent of occurrence (EOO) was estimated to be 2,991 km2 calculated by using CAT (Moat 2007) based on the known extent localities. Six observations have been made recently in North of Behara and in Petriky (F. Rakotonasolo pers. comm. 2008), east of Amboasary main town (H. Ralimanana pers. comm. 2004), North of Taolagnaro in Sainte Luce (S. Rakotoarisoa pers. comm. 2013) and in Petriky and Vinanibe (D. Rabehevitra pers. comm. 2015). All subpopulations are clustered in the South Western region (Taolagnaro and Amboasary-Sud). As each subpopulation is separated by distance 10 to 30 km, five threat-defined locations have been identified.


Countries occurrence:
Native:
Madagascar
Additional data:
Estimated area of occupancy (AOO) - km2:72-631Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:2991
Continuing decline in extent of occurrence (EOO):Yes
Number of Locations:5
Lower elevation limit (metres):1
Upper elevation limit (metres):123
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:

About eight (8) subpopulations have been detected and each subpopulation, separated by 10 to 30 km, consists of less than 50 mature individuals. We don’t have any precision about the exact population size but estimation from recent surveys within several sites shows that there are less than 500 mature individuals left in the natural habitat. The seed is dispersed by wind and as it is fairly heavy this limits long distance dispersal of the species.

Current Population Trend:Decreasing
Additional data:
Number of mature individuals:200-500Continuing decline of mature individuals:Yes
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:This arborescent Aloe grows on sand dunes and littoral limestone (Rauh 1998); in degraded bushland on sand with Opuntia sp., in dry spiny forest with Alluaudia ascendens, A. dumosa and A. comosa on limestone; in humid littoral forest on sand; and in low vegetation on gneiss.
Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: This plant is well-known as an ornamental and can be seen growing in private and botanic gardens outside of Madagascar. The leaves of the plant are used locally on a small scale for medicinal purposes. Although the species is listed in CITES Appendix I, collection of living plants from the wild may happen, but there is no information on how frequently this occurs.

Threats [top]

Major Threat(s):

The species is threatened mainly by habitat destruction due to clearance for agricultural crops. In Taolagnaro (Fort-Dauphin) the mining exploitation affects the habitat of the species as important areas were cleared for the installation of the mining plant and for the exploitation of minerals (Lebigre 2009). The mineral exploitation in the region is a long term activity and may affect other sites where the species occurs such as Petriky (http://www.riotintomadagascar.com/french/aboutQMM.asp). Very few collections of living plants are reported. In some humid areas slash and burn practices and wild fires disturb and destroy the habitat of the species.

Conservation Actions [top]

Conservation Actions: The species is listed in Appendix I of CITES and located within one Protected Area (Petriky). The species also is subjected to ex situ conservation because seeds were collected and banked at the Millennium  Seed Bank in 2004 under the Threatened Plants Project run by the Kew Madagascar Conservation Centre. Also living collection can be seen at the Botanical and Zoological Park of Tsimbazaza in Antananarivo (PBZT) and California Academy of Sciences (CAS) in Madagascar, and a total of 21 collections are known from botanic gardens worldwide (BGCI Plant Search).

Further research is required into the following aspects: the exact population size, the population trends, the international trade, and the uses of the species. Efforts should be undertaken to ensure the conservation of this species in its natural habitat by developing an efficient conservation and management action plan.

Citation: Rakotoarisoa, S.E. 2016. Aloe helenae. The IUCN Red List of Threatened Species 2016: e.T39056A69007588. . Downloaded on 25 July 2017.
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