Hobyo grasslands and shrublands

Content Cover Image

Hobyo Plains, Somalia. (Photograph by Michael Brown/Innovative Resources Management, Inc.)

Introduction

Stretching down the southeast coast from the Horn of Africa, the Hobyo Grassland and Shrubland ecoregion consists of white and orange sand dunes dominated by perennial dune grasslands and sedges. Although unpredictable rainfall and inaccessibility of the area have prevented thorough exploration, less than 1000 vascular plant species are likely to be found here, with high species endemism. This region also supports six endemic species of birds, mammals and reptiles. However, little is known of the current status of this coastal ecoregion, due to political instability.

Location and General Description

This ecoregion is a long, narrow coastal strip from just south of Mogadishu to some 250 kilometers (km) north of Hobyo. It is a low-lying area of coastal plain with dunes of white and orange sand and associated dune grassland. The dunes reach a maximum height of 60 meters (m), and the dune field is about 10 to 15 kilometers (km) wide along its entire length. Inland, the habitat changes to dry savanna and semi-desert vegetation.

caption WWF

Geologically, these are recently deposited sands over Precambrian basement rocks. Where there is soil, it is shallow and recent in origin. Temperature varies little during the year. Here, the climate is hot and dry, with mean maximum temperatures ranging from 30° to 33° C and mean minimum temperatures ranging from 21° to 27° C. Rainfall averages 200 mm annually. It is seasonal, with most rain falling within the period from April to June as the Intertropical Convergence Zone (ITCZ) moves north and south. The area is sparsely populated, with 1 to 20 persons per km2.

Phytogeographically this area is regarded as part of the Somali-Masai regional center of endemism. The vegetation is mapped as deciduous bushland and thicket, although the main components are coastal dune grasslands with scattered bushes, herbs and shrublets. Along the coast, the bushy vegetation has been sandblasted by powerful winds to form a specialized community of low, dense thickets that has year-round low-level green growth due to the humidity of sea breezes. The principal shrubby species are Aerva javanica, Indigofera sparteola, Jatropha pelargoniifolia (glandulosa) and Farsetia longisiliqua.

Biodiversity Features

This area is a center of endemism for plants. Botanical exploration of this region started at the end of the 19th century, but there are no reliable estimates for the number of endemic plants. Unpredictable rainfall (which controls phrenology), political instability, and the physical inaccessibility of the site have hindered explorations. Less than 1000 vascular plant species are estimated to occur here, but these include several endemics and species of phytogeographical interest. Unusual communities grow in mesic limestone gorges, including Buxus hildebrantii, Maytenus undata, and Vepris eugeniifolia. Dirachma somalensis, one of two endangered species in the Dirachmaceae family, has its richest known locality in limestone gorges in this ecoregion. Two other endemics include Amphiasma gracilicaulis and Lochia parvibracta (two other Lochia species are found on Socotra and Oman). Plants have adapted to the climate in several ways. Succulents are common, and the monotypic Puntia genus is found in this ecoregion. Many of the endemics are cushion plants shaped by the sand-laden winds.

There are two strictly endemic reptiles, Haackgreerius miopus and Latastia cherchii, and five other species of reptile that are nearly endemic to this ecoregion. Two strictly endemic mammals are also found, the silver dik-dik (Madoqua piacentinii, VU) and the Somali golden mole (Chlorotalpa tytonis, CR). A number of rare larger mammals are also found: dibatag (Ammodorcas clarkei, VU), Soemmerrings gazelle (Gazella soemmerringii, VU), Salts dikdik (Madoqua saltiana) and Speke's gazelle (Gazella spekei, VU). These all have quite restricted ranges in the Horn of Africa.

There are also two strictly endemic bird species: Ash's lark (Mirafra ashi, EN) and the Obbia lark (Spizocorys obbiensis, DD), which are restricted to the coastal fixed-dune grasslands. The ecoregion thus counts as an Endemic Bird Area, the Central Somali Coast. Although the level of endemism is quite high, the overall number of species in the ecoregion is relatively low.

Current Status

Due to the long-standing and continued political instability in Somalia, it is not known how much habitat remains in this ecoregion, nor how fragmented it has become. The only official protected area is Lag Badana Bush-Bush National Park, but this is undoubtedly no longer functional.

Types and Severity of Threats

No recent information on threats is available. It is known that local populations use the scrub and grassland habitats of the ecoregion to graze their animals and gather fuelwood. The recent political instability and clan warfare in Somalia may have impacted habitats through the displacement of people to the coastal strip from urban centers and from areas further inland.

Justification of Ecoregion Delineation

This ecoregion forms the southernmost section of the Somalia-Masai semi-desert grassland and shrubland vegetation unit of White. It is delineated based on the Central Somali Coast Endemic Bird Area, and is distinct in both its plant and vertebrate composition.

Additional information on this ecoregion

Further Reading

  • Davis, S.D., V.H. Heywood, and A.C. Hamilton (eds.) 1994. Centres of plant diversity. Vol 1: Europe, Africa, Southwest Asia and the Middle East. World Wide Fund for Nature and IUCN, Oxford, UK. 354 pp. ISBN: 2831701988.
  • East, R. (comp.) 1999. African Antelope Database 1998. IUCN/SSC Antelope Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK. ISBN: 2831704774
  • Friis, I. 1992. Forests and Forest Trees of Northeast Tropical Africa. HMSO, Kew Bulletin Additional Series XV.
  • Kingdon, J. 1997. The Kingdon Field Guide to African Mammals. Academic Press, London. 464 pp. ISBN: 0713665130.
  • Lovett, J.C., and I. Friis. 1996. Patterns of endemism in the woody flora of north-east and east Africa. Pp. 582-601. In: L.J.G. van der Maesen et al. (eds.). The Biodiversity of African Plants. The Netherlands: Kluwer Academic Publishers.
  • Stattersfield, A.J., M.J. Crosby, A.J. Long, and D.C. Wege. 1998. Endemic Bird Areas of the World. Priorities for Biodiversity Conservation. BirdLife Conservation Series No. 7. BirdLife International, Cambridge, UK. 846 pp.
  • White, F. 1983. The vegetation of Africa, a descriptive memoir to accompany the UNESCO/AETFAT/UNSO Vegetation Map of Africa (3 Plates, Northwestern Africa, Northeastern Africa, and Southern Africa, 1:5,000,000). UNESCO, Paris.

 

 

Disclaimer: This article is taken wholly from, or contains information that was originally published by, the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

 

 

Glossary

Citation

Fund, W. (2014). Hobyo grasslands and shrublands. Retrieved from http://www.eoearth.org/view/article/153536

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