A biodiversity zonation in the Greater Fish River Canyon Landscape and delineation of environmentally sensitive areas along the Orange River was required for two conservation projects in the Ai-Ais–Richtersveld Transfrontier Park.
This required filling gaps in plant distribution data.
Field surveys of plants were undertaken during the period 2011–2013.
These field surveys generated two cross-border range extensions, which represented new records for Namibia (
These findings highlighted the biodiversity importance of this area at the junction of three major biomes (Succulent Karoo, Desert and Nama Karoo) in the Gariep Centre of Endemism. More stringent reviews of environmental impact assessments are required and associated environmental management guidelines need to be implemented to ensure these newly discovered and rare plants are adequately protected.
The mountains to the west of the Fish River Canyon in southern Namibia are still a very poorly known part of southern Africa’s Great Escarpment (Clark, Barker & Mucina
The study area in southern Namibia presents an approximate triangle around the Namus and Huns mountains and the southern reaches of the Fish River. It is bordered by a section of the lower Orange River in the south (
The Greater Fish River Canyon Landscape and its position in Namibia (circles and band along the Orange River indicate the target areas for plant surveys).
The climate is arid, with a mean annual rainfall between 50 mm and 150 mm, increasing along a south-west to north-east gradient. Summer and winter rains can occur. Mean annual temperatures range between 16 °C and 20 °C, increasing along a west–east gradient. The south-eastern corner of the study area borders one of the hottest areas in Namibia, where temperatures over 36 °C are recorded during the hottest months (Mendelsohn et al.
The topography is rugged and altitudes range from less than 100 m (amsl) at the deeply incised Orange River to 1654 m at the Namuskluft peak. The underlying geology is complex and ranges from the oldest rocks in Namibia to recent Quaternary sediments. In large parts of the study area some sedimentary rocks of the Nama Group (600 Ma–550 Ma) are exposed but there are also gneisses, granites and other metasedimentary rocks of the Namaqua Metamorphic Complex (1800 Ma–1000 Ma) and the Gariep Group (800 Ma–500 Ma), as well as sedimentary rocks and volcanic intrusions of the much younger Karoo Group (345 Ma–140 Ma) (Swart
The vegetation is dominated by succulent dwarf shrubs (mostly in the west) and dwarf shrubs. Grasses become more dominant towards the north and east, as in the Gariep Desert in the Richtersveld (Jürgens et al.
Field surveys were undertaken during the period 2011–2013, with three surveys in the winter season (September–October) and one in the summer season (April–May 2013). These specifically targeted under-collected areas within the study area, which were determined by plotting the collecting status of the national plant specimens database in Namibia and reviewing published sources (Irish
Range extension was determined by reviewing information from the NBRI’s specimens database, which was consolidated and cleaned, BRAHMS online (Craven & Kolberg
Surveys in border regions potentially generate new distribution records, and two new distribution records for Namibia in this study were
The delicate flowers of (a)
Five new or recently described plant species were recorded during these surveys, one a completely new discovery, and the others either not previously recorded in Namibia or without adequate material for taxonomic description.
(a) The delicate
A small species of Iridaceae, growing beneath a granite rock overhang on slopes facing the Orange River, was identified as the new species,
A geophyte that had never been collected before was also discovered during the field surveys growing on mountain slopes near the Orange River and has now been described as
In addition to the cross-border range extensions, the study also generated some range extensions within Namibia. The tall shrub
Species with range extensions as a result of field surveys in the Greater Fish River Canyon Landscape: (a)
New distribution records (triangles) as a result of plant surveys in the Greater Fish River Canyon Landscape (GFRCL) in Namibia: (a)
The fact that new distribution records are generated and new plant species discovered when targeted field collecting is undertaken in the GFRCL emphasises the need for further inventory work. It is evident from the new discoveries that the ephemeral geophyte flora deserves attention, particularly the genus
Although the largest part of this landscape is formally protected, it does not follow that there are no threats to the flora, of which 14% are Namibian endemics and nearly 30% threatened or rare species (of those that had been assessed so far) (Loots
These surveys would not have been possible without the support of Namibia’s National Botanical Research Institute (NBRI), GFRCL stakeholders and Ministry of Environment and Tourism staff in southern Namibia. Leevi Nanyeni’s (NBRI) enthusiastic support in the field deserves particular mention, and the NBRI staff in Windhoek are thanked for their unwavering support, which ensured the identification of the new records, and the use of the NBRI’s specimens database. Namibia’s Ministry of Environment and Tourism gave permission for this research. The author would also like to thank Shakkie Kativu, John Manning, Peter Goldblatt and Leanne Dreyer who identified and described the new species. Comments from three anonymous reviewers and the editor greatly helped to improve the manuscript.
I would like to dedicate this article to the late Maxwell Witbooi (Ministry of Environment & Tourism) who assisted in the most difficult areas to access. Financial support for the field surveys was provided by the SPAN project, Namplace and the Environment Investment Fund of Namibia.
The author declares that she has no financial or personal relationship that may have inappropriately influenced her in writing this article.