Bokh

A(i)Site contains one or more globally threatened species

This site qualifies as an IPA under criterion A(i) due to the presence of two globally threatened species: the socio-economically important tree, Cordeauxia edulis (EN), for which this IPA is a key locality and one of the last remaining sites globally; and Merremia warderensis (CR), for which this site is the only known locality, based on one georeferenced herbarium voucher in the southwestern corner of the IPA, suggesting high site irreplaceability. While further botanical exploration in the region may reveal a more widespread distribution for Merremia warderensis, this site is of global importance for the species.

The Bokh IPA is situated in the Dollo Zone (previously known as the Warder Zone) of Somali Regional State, in the eastern Ethiopian lowlands. It extends across three woredas (districts), namely Bokh, Galadin and Galhamur, and lies approximately 450 km southeast of Jijiga, the capital city of Somali Regional State. Specifically, the IPA borders the towns of Geladin to the south, and Jiracle and Boh to the north, the latter being an important trading centre for local communities and the surrounding areas (Yusuf et al., 2013a).

There are a number of small villages within Bokh IPA, and the eastern part of the site runs parallel to the Ethiopia-Somalia border. Galkayo, Somalia's third-largest city, is located approximately 50 km southeast of the IPA. The Bokh area is one of only two regions thought to still contain the globally threatened tree species, Cordeauxia edulis (EN), which has drastically declined in recent decades and is threatened by livestock farming, resource overexploitation and climate change (Drechsel & Zech, 1988; Beech et al., 2018).

Bokh IPA is situated in the Ogaden, a floristically underexplored territory in eastern Ethiopia, attributable to decades of security issues and socio-political tensions (Sebsebe & Dioli, 2000; Mabberley, 2009). Across the Ogaden, the abundance of endemic plant species is thought to be higher than in most other areas of Ethiopia, with great potential for the discovery of new species (Dioli, 2002; Thulin, 2011; cited in Thulin & Vollesen, 2015; Friis et al., 2016).

The IPA is a key locality for the socio-economically important tree, Cordeauxia edulis (EN), locally known as Yeheb (Drechsel & Zech, 1988; Mekonnen et al., 2010; Yusuf et al., 2013b; Seyoum & Mekbib, 2014; Beech et al., 2018). This species was once widespread throughout the Ogaden, extending into central Somalia, but by 1988 the species' distributional range had declined significantly, with only two known localities in Ethiopia - the Werder and Bokh regions (Drechsel & Zech, 1988). The current distribution of Cordeauxia edulis in Ethiopia may, in fact, now be restricted to the Bokh region (Mekonnen et al., 2010; Yusuf et al., 2013b; Sebsebe Demissew, pers. comm.). Fieldwork in June 2021 revealed the presence of Cordeauxia edulis at six sites within the IPA: near Mirafadle Kebele, Gambarey, Maned Kebele, Dabhabalan Kebele, Foya adde Kebele and Shilinbur (Abubaker et al., 2021).

The endemic geophyte, Merremia warderensis (CR), is also known to occur in the surrounding areas, supported by a herbarium voucher from the southwestern corner of the IPA (Sebsebe, 2001). Further fieldwork is required to determine the abundance and distribution of this species.

The topology of the IPA is characterised by desert to semi-desert lowlands. White (1983) and Friis et al. (2010) categorised the area as a mix of Acacia-Commiphora woodland and bushland, and desert and semi-desert scrubland. Land cover within the IPA consists of Haud-type mixed bushland (Acacia-Commiphora), open scrubland and grassland, rocky outcrops and urban areas. The Acacia-Commiphora bushland, also referred to as Haud-type mixed bushland by Drechsel & Zech (1988), varies from thickets to low open scrub, dominated by drought resistant and semi-succulent species. Open grassland is dominated by Aristida kelleri, Aristida paoliana and Stipagrostis uniplumis (Hemming, 1966; Drechsel & Zech, 1988). Other grasses include Cenchrus ciliaris, Cenchrus stramineus, Dactyloctenium scindicum, Digitaria rivae, Eragrostis papposa, Leptothrium senegalense, Tetrapogon cenchriformis and Tetrapogon roxburghiana (Hemming, 1966).

In addition to Cordeauxia edulis, scattered thickets across the Bokh region comprise Albizia anthelmintic (LC), Balanites rotundifolia var. scillin, Cordyla somalensis (NT), Delonix baccal, Euphorbia cuneata (LC), Fagonia lahovari, Gyrocarpus hababensis, Indigofera ruspoli, Senna italica, Sesamothamnus rivae, Terminalia orbicularis, Vachellia (Acacia) horrida, Vachellia (Acacia) tortilis (LC) and various species of Boswellia, Commiphora, Cordia and Grewia (Hemming, 1966; Drechsel & Zech, 1988; Yusuf et al., 2013b). Where Cordeauxia edulis is locally abundant, the density of other tree species appears to be relatively low, whereas in areas where Yeheb has been locally overexploited (for instance, the villages of Foye ade, Maned and Dab-habalan), other species begin to dominate (Abubaker et al., 2021). These include Acacia horrida, Acacia tortilis (LC), Boswellia microphylla, Boswellia neglecta, Cassia obovata, Cordia africana (LC), Euphorbia cuneata (LC), Indigofera ruspoli, Terminalia orbicularis and a number of Commiphora species (Abubaker et al., 2021).

Lithologically, the area is dominated by the Bokh formation, comprising shale interbedded with sandstone and siltstone (Worku & Astin, 1992; JICA, 2013; Oljira et al., 2020). Gypsum and limestone outcrops are also widely exposed in the Bokh and Galadi woredas (Hemming, 1966; Drechsel & Zech, 1988; JICA, 2013). According to Drechsel & Zech (1988), soil within the IPA is characteristic of the Haud, consisting of red sandy soil, with a high rainwater filtration rate, derived from the Jesomma formation. The red soils of the Galadin woreda are often deeper, with traces of lime (Drechsel & Zech, 1988). Petric and haplic gypsosols also occur.

The climate of the Bokh area is arid, part of the Bereha climatic zone (Mege et al., 2015), with a mean annual temperature of 28 C (Yusuf et al., 2013b). Rainfall is bimodal with two rainy seasons (March-May and October-November), and two prolonged dry periods (Drechsel & Zech, 1988; Seyoum & Mekbib, 2014). Mean annual rainfall varies from 150-250 mm (Drechsel & Zech, 1988; Yusuf et al., 2013b).

There is currently no site protection or biodiversity management plan within the IPA, nor does the IPA overlap with an Important Bird Area or Key Biodiversity Area. This is perhaps, in part, a result of the socio-political tensions and territorial disputes that have presided over the region for many years, hampering botanical exploration and conservation efforts (Hogg, 1991; Mabberley, 2009; Mohamed & Iman, 2010; Mohamed, 2013). The region is also prone to prolonged periods of drought, likely exacerbated by increasing weather unpredictability and climate change. Cordeauxia edulis is considered to be relatively drought resistant and desertification tolerant (Yusuf et al., 2013; Abubaker et al., 2021), but it remains unclear how future climatic changes will affect the species.

Overgrazing from livestock is the main threat to Bokh IPA and its floristic diversity. Over 85% of the human population across the Ogaden are pastoralists (Yusuf et al., 2013a), exerting significant pressures on the region's natural habitat. The globally threatened species, Cordeauxia edulis (EN), has declined by 50% over just three generations (less than 180 years) due to overexploitation by local communities, overgrazing and severe droughts (Thulin & Vollesen, 2015; Beech et al., 2018).

The ecosystem services provided by this site are poorly documented. Given that the majority of the local population are pastoralists, most of the land is utilised as pastureland (Yusuf et al., 2013a). Cordeauxia edulis is a socio-economically important tree, utilised as fodder for livestock and the seeds harvested for market trade at Bokh or Galkayo, just across the border in Somalia. This species, locally known as Yeheb, also has medicinal properties and is used in construction and as fuel, and as a food source in a variety of forms (Alemu et al., 2022).

At least two dry oil wells are known to exist in or around the IPA, one at Galadin (which initially produced oil before being abandoned in the 1950s), and one at Bokh (abandoned June 1965) (Purcell, 1979). Oljira et al. (2020) reported that while the area is now unlikely to contain significant reserves of crude oil, natural gas may be found. There is no known tourism and, due to issues of inaccessibility and security, this is unlikely to change in the near future.

Joe Langley, Royal Botanic Gardens, Kew

Eden House, Royal Botanic Gardens, Kew

Iain Darbyshire, Royal Botanic Gardens, Kew

Sebsebe Demissew, Addis Ababa University

Sileshi Nemomissa, Addis Ababa University

Ermias Lulekal, Addis Ababa University