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Ravenea rivularis 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Liliopsida Arecales Palmae

Scientific Name: Ravenea rivularis Jum. & H.Perrier
Common Name(s):
English Majestic Palm, Majesty Palm

Assessment Information [top]

Red List Category & Criteria: Vulnerable B2ab(i,ii,iii,iv,v) ver 3.1
Year Published: 2017
Date Assessed: 2017-02-22
Assessor(s): Phillipson, P.
Reviewer(s): Manjato, N.
Justification:
Known from five somewhat fragmented areas in the west of Madagascar representing ten locations with an estimated extent of occurrence of 46,800 km² and area of occupancy of 117 km². The species may be locally abundant, notably the recently discovered subpopulation in Namoroka - a well-established protected area, and in the Makay Massif - an area that has been proposed but is not yet accepted as a new protected area. The subpopulation in Isalo is situated at the edge of the National Park and is subjected to numerous ongoing threats of which wild fire and artisanal mining are probably the most serious, and there is continuing decline in the extent and quality of the habitat and in numbers of mature individuals here and in most of the known locations. On the basis of its restricted AOOand the continuing decline found at most of the limited number of locations, the species is therefore assessed as Vulnerable. This is also one of the most popular palm species from Madagascar in international horticulture, and although there are strict trade regulations in place, illegal harvest of seed from the wild still occurs and may impact natural regeneration.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Endemic to humid habitats in the dry and subarid west of Madagascar, known mainly from the area between Isalo, Sakaraha and Makay in Toliara Province (Dransfield, J. and Beentje, H.,1995), but recently discovered in the Namoroka National Park, near Soalala, Mahajanga Province (Madagascar Catalogue, 2016). In addition to localities represented by collection data, reliable observations (Rajaonary et al. 2005) indicate that the species is also present in Zombitse - Vohibasia National Park and this information is included in this assessment. Other historical observations of the species from Mahajanga Province are unconfirmed and imprecise, these are not included here. Distribution data now available shows that the species has a much larger range than previously known and has rendered the previous threat assessments invalid.
Countries occurrence:
Native:
Madagascar
Additional data:
Estimated area of occupancy (AOO) - km2:108Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:46800
Continuing decline in extent of occurrence (EOO):Yes
Number of Locations:10
Lower elevation limit (metres):135
Upper elevation limit (metres):840
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:About 900 mature trees were estimated across all the known sites for the 2010 assessment and the population was declining. Since that time additional important subpopulations have been discovered, notably in Makay and Namoroka (Madagascar Catalogue, 2016), and the species has also been recorded from Zombitse - Vohibasia National Park and adjacent to the Analavelona Protected Area. Nevertheless, the subpopulations in protected areas are all situated at the edge of these areas, and it is not known whether the species is also present within the core of the protected areas concerned where they would be more adequately protected. There is a considerable gap between the newly discovered sub-population at Namoroka and the other sub-populations, but much of the intervening habitat that is likely to contain suitable habitat is known to be severely degraded.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Population severely fragmented:No
Continuing decline in subpopulations:Yes

Habitat and Ecology [top]

Habitat and Ecology:Usually found on river-banks in lowland forest, but also grows in shallow and slow moving water and along streams in deep canyons and in swamp forest with flowing water. Recorded at elevations from 135 to 840 m asl. A study of seed production and germination was conducted by Guy Rakotondranony, which may provide useful information, and the recently discovered subpopulation at Namoroka was observed to have a prolific seedling production.
Systems:Terrestrial; Freshwater
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: This is one of the most sought after Malagasy palm species in international horticulture. Seed is harvested from the wild for trade. The species is listed on CITES Appendix II.

Threats [top]

Major Threat(s): The threats to this species include habitat loss through wild fires, drilling for oil, mining and the harvest of seeds from the wild for the horticultural trade which may impact the regeneration potential of the species.

Conservation Actions [top]

Conservation Actions: The subpopulation at Isalo is on the margin of the National Park, but the Park is currently subject to illegal artisanal mining and wild fires that threaten its natural habitats. In Zombitse - Vohibasia the species has been recorded at the edge of the protected area at Isoky, in an area that that is partially cleared for agriculture. The species has been recorded near to the Analavelona, but not within the formally protected area. The extent of the species in Makay where a large area of suitable habitat is believed to exist, may comprise large subpopulations of considerable importance for conservation, the area is poorly explored and this requires further investigation. Part of Makay has been proposed for incorporation into the protected area network, but the site has also been prospected for oil and possible future exploitation of this resource may impact the species. Monitoring of the harvesting of wild-collected seeds is required and possible additional enforcement of the controls. The recently discovered sub-population in Namoroka is limited in extent and is situated at the edge of the National Park (Madagascar Catalogue, 2016), but it is apparently currently not threatened.

Citation: Phillipson, P. 2017. Ravenea rivularis. The IUCN Red List of Threatened Species 2017: e.T38677A67737451. . Downloaded on 22 October 2017.
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