The ecoregion occupies moderate elevations in the peninsula's mountainous southwest, which include regions such as the Hejaz.
In Hadhramaut and Dhofar, the terrain is mostly sedimentary, including limestones, sandstones, bauxite and conglomerates over a base of older Precambrian igneous and metamorphic rocks.
They consist of drought-deciduous open woodlands and thorn scrub, with species of the genera Acacia and Commiphora predominant.
Other trees and shrubs include Euphorbia cuneata, Euphorbia triaculeata, Grewia tenax, Hibiscus micranthus, Maytenus senegalensis, Melhania denhami, Dobera glabra, Aloe spp., Cadaba farinosa, Boscia arabica, Adenium obesum, Barleria spp., Boswellia carteri, Maerua crassifolia, Olea europaea, Balanites aegyptiaca, Cupressus sempervirens, Salix alba, Juglans regia, Populus alba, Populus nigra, Quercus coccifera, Quercus ilex, Quercus pubescens, Pistacia terebinthus, Juniperus communis, Ceratonia siliqua, Arbutus unedo, Erica arborea, Phoenix canariensis, Phoenix dactylifera, Laurus nobilis, Ziziphus spina-christi, Prosopis cineraria, Pinus halepensis, Pinus pinea, Pinus nigra, Aerva javanica, Prunus amygdalus, Corylus avellana, Sclerocarya birrea, Ficus salicifolia, Faidherbia albida, Borassus aethiopum, Vitellaria paradoxa, Afzelia africana, Kigelia africana, Adansonia digitata, and Sterculia africana.
The higher humidity sustains semi-deciduous woodlands between 500 and 900 meters elevation, dominated by the endemic tree Terminalia dhofarica, together with Carissa edulis, Dodonaea viscosa, Euclea racemosa subsp.
[8] Acacia-Commiphora woodlands continue up to 1800 meters elevation, and these higher-elevation woodlands are characterized by Senegalia asak, S. etbaica, Vachellia tortilis, Commiphora gileadensis, C. myrrha, Moringa peregrina, Searsia tripartita, Dobera glabra, Euphorbia cuneata, Grewia villosa, Cadia purpurea, Carissa edulis, Cordia abyssinica, and Terminalia brownii.
Seasonal watercourses, or wadis, are lined with Breonadia salicina, Cordia abyssinica, Ficus vasta, and Mimusops laurifolia.
[14] Scortecci's toad (Bufo scorteccii) is an endemic species known only from one location – Wadi al Khalili on a high plateau near Mafhaq (1,550 meters elevation) in northern Yemen.
[16] Local people created terraced fields on steep slopes in areas of relatively high rainfall, and irrigated farms in the lower reaches of streams descending from the mountains.
[17][18] The woodlands have been degraded and reduced in area by overharvesting trees for timber and firewood, livestock grazing, and conversion to agriculture, particularly around the ecoregion's cities.