The decline of the Vulnerable yeheb Cordeauxia edulis, an economically important dryland shrub of Ethiopia M USSA Y USUF,ZEWGE T EKLEHAIMANOT and D ERIBE G URMU Abstract Cordeauxia edulis (Leguminosae: Caesalpinioideae), long time where individual stems cannot survive for a long commonly called yeheb, is a small tree/shrub species endemic period or establishment of new shrubs by seedlings is to Ethiopia and Somalia. The tree produces nuts that are difficult because of the harsh climate and edaphic consumed as a staple food by pastoralists and are sold in local conditions, and grazing pressure. Thus, assessment of the markets. Recent reports indicate that C. edulis has vanished size class distribution of stems within clumps can be used to from many locations where it was noted by earlier travellers determine whether or not the population of a shrub species and, as a result, it is currently categorized as Vulnerable on the is in decline. An even distribution of size classes indicates IUCN Red List. To assess the current status of the species we that the species is in a condition of stable self-maintenance. studied it around 10 villages in Boh district in the Somali A greater number of stems of clumps in higher size classes Regional State of Ethiopia, where the only known remnant compared to lower size classes reflects a decline in self- stands of C. edulis in Ethiopia are found. The results show that maintenance ability. If such a trend continues a population these populations of C. edulis are declining and natural could go extinct locally (Fujiki & Kikuzawa, 2006). regeneration is negligible. We recommend that yeheb should Assessment of regeneration status from the population becategorizedasEndangeredontheIUCNRedList,basedon dynamics of seedlings is a further means by which the status criteria A1d, because we estimate that there has been at least a of the population of a plant species can be determined. A 70% reduction in population size from overexploitation. The population structure characterized by the presence of a major constraints to natural regeneration and imbalance in the sufficient number of seedlings indicates satisfactory regen- population structure are over-harvesting of immature nuts, eration or a stable population whereas an inadequate excessive browsing of shoots and leaves by livestock and number of seedlings indicates poor regeneration or a excessive cutting of wood for fuel and construction. We declining population (Swaine et al., 1990). recommend that conservation measures for the species focus Cordeauxia edulis Hemsley, locally called yeheb, is a on sustainable harvesting of mature nuts, raising awareness small evergreen multi-stemmed tree or shrub (Ali, 1988, among local people, preservation and monitoring of remnant cited in Liew, 2003) of the legume subfamily populations and introduction of the species in ecologically Caesalpinioideae, endemic to eastern Ethiopia and central suitable sites. Somalia. It is drought hardy and a source of food for both animals and humans (NAS, 1979). The tree produces nuts Keywords Caesalpinioideae, Cordeauxia edulis, Ethiopia, that are collected and consumed as a staple food by nuts, population density, regeneration, size class distri- pastoralists and sold in local markets to provide household bution income. Because of high demand and competition, the fruits of C. edulis are usually collected prematurely (Kazmi, 1979). Yeheb foliage is a preferred browse for camels and goats, Introduction which are the dominant livestock in the region, and is 2010 clump of a shrub species always consists of stems of heavily browsed throughout the year (Yusuf, ). The ff wood of yeheb is also a preferred building material because Adi erent ages and sizes as old stems are replaced 2010 with newly sprouted stems. In drylands this allows it is termite resistant (Yusuf, ). C. edulis is the only species in the genus (Bally, 1966) and is dominant or co- multi-stemmed shrub species to maintain themselves for a dominant in the deciduous Acacia–Commiphora bushland vegetation of the Somali–Masai floristic zone (White, 1983). 1930 MUSSA YUSUF Somali Region Pastoral Agropastoral Research Institute, Jigjiga, Since the s it has declined over most of its original range Ethiopia and has disappeared from many locations where it was ZEWGE TEKLEHAIMANOT (Corresponding author) School of the Environment, noted by earlier travellers (Bally, 1966). Natural Resources and Geography, Bangor University, UK. The species is threatened by several factors, including E-mail [email protected] drought, grazing and over-harvesting of nuts (Bally, 1966; DERIBE GURMU Forestry Research Centre, Ethiopian Agricultural Research 1979 1998 Organisation, Addis Ababa, Ethiopia NAS, ; Walter & Gillett, ). Although it is categorized as Vulnerable on the IUCN Red List its status Received 17 January 2011. Revision requested 11 February 2011. Accepted 15 March 2011. has not been assessed since 1998, and requires updating © 2013 Fauna & Flora International, Oryx, 47(1), 54–58 doi:10.1017/S0030605311000664 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.14, on 28 Sep 2021 at 00:08:26, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605311000664 A Vulnerable Ethiopian shrub 55 (WCMC, 1998). Because of its high nutritional value and number and direction in all 10 populations. The transect line economic importance attempts to grow the species have started from the edge of the village settlement in a direction been made in Kenya, Tanzania and Israel (Nerd et al., 1994), best representing all target areas, including areas close to the Sudan, Yemen, India, Australia and the USA (Veitmeyer, settlement and those further away. According to Brink 1985;FAO,1988). The seeds appear to germinate well (up to (2006) and Ali (1988, cited in Liew, 2003) proximity to a 80% germination) but establishing the seedlings in the field village is one of the factors that influences the density of has been less successful. Thus, the species is still confined to yeheb. its natural range in Somalia and Ethiopia. As there are no In the early stages of growth yeheb is reported to be published reports of field assessments of the status of the single-stemmed whereas mature plants are multi-stemmed, species a study of the population structure and regeneration with most of the stems arising from the base of the plant status of yeheb was therefore undertaken during 2007–2008 near the ground (Ali, 1988, cited in Liew, 2003). Each in Boh District of the Somali region of Ethiopia. separate clump of stems thus constitutes an individual adult plant. Therefore, within each quadrat all clumps of yeheb $ 2 Study area with stems per clump, and single-stemmed individuals, were counted. The number of stems in each clump was Boh district, in the Somali Regional State, is the only place recorded along with the basal diameter of each. Other where yeheb now occurs in Ethiopia. Over 85% of the species of trees and shrubs growing with yeheb in each human population of Boh is pastoralist and dependent upon quadrat were identified and the number of individuals of livestock. The area is arid, with a total annual rainfall of each species counted. 150–250 mm that falls in two rainy seasons of varying Frequencies and densities by basal diameter classes were reliability; the two pronounced dry seasons are each of at computed and skewness coefficients calculated to examine least 5 months duration. The south-west monsoon brings the size distribution. An analysis of variance was used to the main rains in March/April to May/June; the north-east examine variation between populations and Tukey’s test was monsoon brings rain in October–November. The area is used to make pairwise comparison between means to test frost free with a mean annual temperature of 28 °C. Altitude the hypothesis that there are no differences in density and −1 is 300–1,000 m. The mean monthly wind speed is 2–3 km h size class between populations. except during the south-west monsoon, when it is 4–5 −1 km h . Mean annual potential evapotranspiration is Results 1,700–2,600 mm (Drechsel & Zech, 1988; Yusuf, 2010). A total of 67 clumps of yeheb were enumerated in the 10 67 −1 Methods populations, giving a mean density of clumps ha (range 30–110; Table 1). The ANOVA indicated there was no Members of the agropastoral extension staff of the Somali significant difference in the density of clumps between Regional State and knowledgeable villagers and clan leaders populations. A total of 1,059 stems were enumerated in the 10 were contacted to make enquiries about the occurrence of populations. The mean number of stems per clump was yeheb in the region. All responses confirmed that the species 16 ± SE 1.62. The ANOVA indicated that the mean stem basal is only found in Boh district, the region where Captain diameter (Table 1)differed significantly between populations. Cordeaux obtained botanical specimens in July 1907 (Bally, The majority of stems were of intermediate basal diameter; 1966). Following this confirmation we made a preliminary the skewness coefficient of the distribution was −0.43.One reconnaissance to identify the locations of the stands of single-stemmed plant was found in one quadrat in each of yeheb. Of the 72 villages in the district yeheb was found only four of the 10 populations (Maned, Gambare, Mirafadle and in 10 (a village is the smallest administrative unit after Dudun) and none in the other six populations. district and includes the settled area and the surrounding A total of 16 other tree and shrub species were found environment), in an area from approximately 46.6°E 7.0°N growing with yeheb in the 100 quadrats (Table 2). Acacia to 47.2°E 7.4°N. We conducted this study in all 10 of these tortilis and Boswellia neglecta were the most common villages.