Southwest Arabian coastal xeric shrublands

The Aldabra Island xeric scrub covers the coral atoll of Aldabra in the Seychelles, an isolated landform in the western Indian Ocean lying roughly 400 km northwest of Madagascar. Its xeric vegetation falls into two main types: dense thickets of Pemphis acidula on the saline, low-lying ground, and a mixed scrub of low trees, shrubs, herbs, and grasses spread across most of the atoll. The climate is tropical, with an average annual temperature near 27 degrees Celsius and about 1,200 mm of rainfall, split into a wetter season from November to April and a drier stretch from May to October. The terrestrial flora includes roughly nine fern species and 178 flowering plants, of which about 38 percent are thought to be endemic. Aldabra is best known for hosting the world's largest population of giant tortoises and the flightless Aldabra white-throated rail, and the atoll has been protected as a UNESCO World Heritage Site since 1982.

The Djibouti xeric shrublands form a semi-desert belt along the Red Sea and Gulf of Aden coasts of the Horn of Africa, spanning Djibouti, Eritrea, Ethiopia, and Somalia (including Somaliland) and encompassing the Afar Triangle, a lowland that drops as much as 160 metres below sea level at fault depressions such as the Danakil and Lac Assal. Vegetation grades from coastal mangroves into open grass and shrub steppe, with thorny acacias such as Acacia (Vachellia) tortilis and Senegalia mellifera, the spiny Rhigozum somalense, and the desert date Balanites aegyptiaca characteristic of the sandy plains and basaltic lava fields. The climate is extremely hot and arid, with mean annual rainfall ranging from under 100 millimetres near the coast to around 200 millimetres further inland, and the tectonically active rift includes some of the hottest sites in Africa. The ecoregion is notable for harboring the last viable population of the African wild ass alongside the endemic Archer's lark and the dragon tree Dracaena ombet, which clings to higher arid hills. For gardeners in hot, dry climates, several drought-adapted natives here-the architectural Dracaena dragon trees and tough Acacia and Balanites genera-are familiar xeric ornamentals.

The Eritrean coastal desert is a narrow, arid strip running along the southern Red Sea coast of Eritrea and Djibouti, a flat sand-and-gravel plain lying below about 200 metres and broken by rocky outcrops. Vegetation is sparse herbaceous steppe dotted with scattered umbrella thorn (Acacia tortilis) and Acacia asak, alongside drought-hardy grasses such as Panicum turgidum, Cymbopogon schoenanthus, and Lasiurus scindicus, with halophytic plants and small mangrove stands in sheltered coastal creeks. The climate is extremely hot and dry, with annual rainfall averaging under 100 millimetres and highly variable from year to year, and minimum temperatures among the highest recorded anywhere in Africa. Despite the harsh setting, the region still supports Dorcas and Soemmerring's gazelles along with the diminutive Salt's dik-dik, and the adjacent Bab-el-Mandeb Strait channels one of the world's largest intercontinental raptor migrations each autumn, when hundreds of thousands of birds of prey cross from Arabia into Africa. For gardeners in hot, dry climates, the native umbrella thorn acacias and clumping desert grasses found here illustrate the kind of heat- and drought-tolerant planting the region naturally favours.

The Gariep Karoo is an arid, open shrubland in the Afrotropic realm that stretches from the middle of South Africa's Northern Cape northward across the Orange River (also called the Gariep River, which forms the border between the Northern Cape and Namibia's ǁKaras Region) into southern Namibia. Its sparse, low-shrub vegetation is dominated by succulent dwarf shrubs and tall stem-succulents including quiver trees, with characteristic genera such as Drosanthemum, Eriocephalus, Galenia, Pentzia, Pteronia and Ruschia, alongside perennial grasses like Aristida and Stipagrostis. The climate is harsh, with mid-summer maximum temperatures exceeding 36 degrees Celsius, mid-winter minimums dropping below freezing, frequent droughts, and annual rainfall between 50 and 500 millimetres that decreases from east to west. The region holds the dramatic Fish River Canyon in southern Namibia and supports the ferruginous lark, its endemic flagship bird, yet it remains poorly protected against a 40 percent conservation target. For gardeners in dry climates, its drought-hardy natives such as quiver trees and succulent shrubs in the genera Ruschia and Drosanthemum are well suited to xeric, low-water plantings.

The Hobyo grasslands and shrublands form a long, narrow coastal strip in Somalia, running along the Indian Ocean from south of Mogadishu northwards past the town of Hobyo, where a belt of wind-built dunes some 10 to 15 kilometers wide fringes the shore. The dunes carry distinctive grassland and low scrub: wind-tolerant grasses and sedges first colonize the bare sand, while denser thickets of Aerva javanica, Indigofera sparteola, and Jatropha pelargoniifolia hold the more stable ground. The climate is hot and dry, with rainfall concentrated in a short April-to-June season as the Intertropical Convergence Zone shifts north. Part of the Somali-Masai centre of plant endemism, the ecoregion shelters several species found nowhere else, including the silver dik-dik, the Somali golden mole, and the endemic Ash's lark and Obbia lark, yet it lies almost entirely outside any protected area. Gardeners working hot, sandy, low-water sites may recognize relatives of its native dune flora, such as the drought-hardy Aerva and Indigofera.

This Afrotropic desert and xeric shrubland ecoregion covers two small coralline islands, Europa and Bassas da India, a French overseas territory scattered in the Mozambique Channel about a third of the way from southern Madagascar toward southern Mozambique, with the two islands lying roughly 100 km apart. The low-lying landscape of Europa is clothed in dry forest of silver thicket (Euphorbia stenoclada), a grassy herbaceous formation of Sclerodactylon macrostachyum, coastal shrubland including bay cedar (Suriana maritima), and mangrove swamps of Rhizophora mucronata fringing a shallow lagoon open to the sea. The climate is semi-arid and tropical with wet summers and dry winters, dominated by southeast trade winds in the austral winter and the occasional cyclone. The islands are an internationally important refuge: Europa is one of the world's largest nesting grounds for green sea turtles and hosts a major great frigatebird colony along with endemic lizards and seabirds, and the area is protected as a Ramsar wetland. For gardeners, the native flora here is dominated by drought-tolerant succulent Euphorbia and salt-tolerant coastal genera adapted to heat and limited rainfall.