TheEthiopian Highlands (also called theAbyssinian Highlands)[1][2] is a rugged mass ofmountains extending fromEthiopia toEritrea inNortheast Africa. It forms the largest continuous area of its elevation in the continent, with little of its surface falling below 1,500 m (4,900 ft), while the summits reach heights of up to 4,550 m (14,930 ft). It is sometimes called the "Roof of Africa" due to its height and large area.[3] Ethiopia is the only country in the region with such a high elevated surface. This elevated surface is bisected diagonally by the Great East African Rift System which extends from Syria to Mozambique across the East African Lakes. Most of the Ethiopian Highlands are part of central and northern Ethiopia, with theEritrean Highlands as its northernmost portion. TheEthiopia-Yemen Continental Flood Basalts[4] are shared between the Horn of Africa and highlands ofUpper Yemen along with the cultural, historical, and genetic ties of the two regions on opposite ends of theRed Sea.
In the southern parts of the Ethiopian Highlands once was located theKingdom of Kaffa, a medieval andearly modern state, whence thecoffee plant was exported to theArabian Peninsula. The land of the former kingdom is mountainous with stretches of forest. The land is very fertile, capable of three harvests a year. The termcoffee derives from theArabic:قهوة (qahwah)[5] and is traced to Kaffa.[5][6]
In theAmhara region to the north, genetic adaptation (e.g., rs10803083, anSNP associated with the rate and function ofhemoglobin; BHLHE41, a gene associated withcircadian rhythm andhypoxia response; EGNL1, a gene strongly associated with oxygenhomeostasis in mammals) to hypoxia and lowatmospheric pressure has been found among theAmhara people, which may have developed within the past 5000 years.[7]
The Highlands are divided into northwestern and southeastern portions by theMain Ethiopian Rift, which contains a number of salt lakes. The northwestern portion, known as the Abyssinian Massif,[8] includes theSemien Mountains, part of which has been designated theSimien Mountains National Park. Its summit,Ras Dashen (4,550 m), is the highest peak in Ethiopia.Lake Tana, the source of theBlue Nile, also lies in the northwestern portion of the Ethiopian Highlands.
The southeastern portion is known as the Harar Massif.[8] It's bounded in the west, by the fault line of the Rift Valley, in the east, by the Ogaden Lowlands and in the south, by the Elkerie and Borena Lowlands. Its highest peaks are located in theBale Zone of Ethiopia'sOromia Region. TheBale Mountains, also designateda national park, are nearly as high as those of Semien. It is the main source of the Wabishebelle and Genalle (Juba). The range includes peaks of over 4,000 m. Among the former areMount Tullu Demtu (4,337 m), which is the second-highest major independent mountain in Ethiopia, andMount Batu (4,307 m).
Most of the country's major cities are located at elevations of around 2,000–2,500 m (6,600–8,200 ft) above sea level, includingAddis Ababa, Ethiopia's capital and largest city, and historic capitals such asGondar andAxum.
Dendi Caldera, a collapsed volcano in the mountain region
The Ethiopian Highlands began to rise 75 million years ago,[9] as magma from the Earth's mantle uplifted a broad dome of the ancient rocks of theArabian-Nubian Shield. The opening of theGreat Rift Valley split the dome of the Ethiopian Highlands into three parts; the mountains of the southernArabian Peninsula are geologically part of the ancient Ethiopian Highlands, separated by the rifting which created theRed Sea andGulf of Aden and separated Africa from Arabia.
Around 30 million years ago, aflood basalt plateau began to form, piling layers upon layers of voluminous fissure-fedbasaltic lava flows. Most of the flows weretholeiitic, save for a thin layer of alkali basalts and minor amounts offelsic (high-silica) volcanic rocks, such asrhyolite. In the waning stages of the flood basalt episode, large explosivecaldera-forming eruptions also occurred.
The Ethiopian Highlands were eventually bisected by the Great Rift Valley as the African continental crust pulled apart. This rifting gave rise to largealkaline basaltshield volcanoes beginning about 30–31 million years ago.[10]
Spatial distribution of temperature in Ethiopia is determined primarily by altitude and latitude. Altitude is the main factor that determines the spatial distribution of temperature in Ethiopia. Ethiopia lies within the tropics, a zone of maximum insolation, where every place has overhead sun twice a year. However, considerable portions of Ethiopia are highland areas, and their altitudes give them non-tropical temperatures. Ethiopia's tropical climate occur in lowlands at the country's peripheries. The predominant climate of the Ethiopian Highlands is theAlpine climate.
Because the highlands elevate Ethiopia, located close to theequator, this has resulted in giving this country an unexpectedly temperateclimate. Further, these mountains catch the precipitation of themonsoon winds of theIndian Ocean, resulting in arainy season that lasts from June until mid-September.[11] These heavy rains cause theNile toflood in the summer, a phenomenon that puzzled theancient Greeks, as the summer is the driest season in theMediterranean climate that they knew.
Ethiopian Highlands withRas Dashen in the background
The Ethiopian Highlands share a similar flora and fauna to other mountainous regions of Africa; this distinctive flora and fauna is known asAfromontane, but from the time of the lastice age the region has been populated with some Eurasian (palearctic) flora. The habitats are somewhat different on either side of the Great Rift Valley which splits the highlands.
The highlands themselves are divided into three distinctecoregions, distinguished by elevation. TheEthiopian montane forests lie between 1,100 and 1,800 meters elevation, above the lowland grasslands and savannas, and extend to areas of similar habitat in Eritrea, Sudan, and Djibouti. This woodland belt has several natural plant communities, but has mostly been heavily grazed and converted to agricultural use now.Kolla is an open woodland found at lower elevations, and is dominated by species ofTerminalia,Commiphora,Boswellia, andAcacia.Weyna dega is a woodland found in moister and higher locations, dominated by theconifersAfrocarpus gracilior andJuniperus procera. The lower portion of theHarenna Forest is a distinct woodland community, with an open canopy ofWarburgia ugandensis,Croton macrostachyus,Syzygium guineense, andAfrocarpus gracilior, withwild coffee (Coffea arabica) as the dominant understory shrub. The southwesterly winds bring rainfall from May to October with moisture from the Red Sea coming in from the east year round.Fauna at these elevations includes the endemicHarwood's spurfowl (Pternistis harwoodi), PrinceRuspoli's turaco (Tauraco ruspolii) andyellow-throated seedeater (Serinus flavigula)[12]
TheEthiopian montane grasslands and woodlands is the largest of the highland ecoregions, occupying the area between 1,800 and 3,000 meters elevation. The natural vegetation was closed-canopy forest in moister areas, and grassland, bushland, and thicket in drier areas. However these hillsides have good fertile soil and are heavily populated, largely by farming communities, so most of the region has been converted to agriculture with a few areas of natural vegetation remaining. Urban areas in this ecoregion include: Ethiopia's capital city and Africa's fourth largest cityAddis Ababa, theAmhara Region capitalBahir Dar with its island monasteries onLake Tana, the old walled city ofHarar, the spa town ofAmbo,Asella in theArsi Zone, the trekking center ofDodola, the lakesideBishoftu, the largest city in the southwestJimma, the market town ofNekemte, and the capital of theTigray Region,Mek'ele.Awash National Park is a site for birdwatching.
Remaining woodland in the drier areas contains much endemic flora and primarily consists of the conifersAfrocarpus falcatus andJuniperus procera, often with the broadleavedHagenia abyssinica. In theHarenna Forest, pockets of moist, closed-canopy forest withAningeria andOlea are draped withlianas andepiphytes, while above 2,400 meters, a shrubby zone is home toHagenia,Astropanax, and giantlobelias (Lobelia gibberroa), species which can be found on theEast African mountains further south. The evergreen broadleaved forest of theSemien Mountains, between 2,300 and 2,700 meters elevation, is dominated bySyzygium guineense,Arundinarial,Juniperus procera, andOlea africana.
Above 3,000 meters elevation lie the highEthiopian montane moorlands, the largestAfroalpine region in Africa. The montane moorlands lie above the tree line, and consist of grassland andmoorland with abundant herbs and some shrubs that have adapted to the high mountain conditions. In Ethiopia, Afroalpine and Sub-Afroalpine vegetations are found in the Highlands of Semein and Highlands of Bale.
These slopes are home to a number of endemic wildlife species, including the endangeredwalia ibex (Capra walie) and thegelada baboon, whose thick fur allows it to thrive in the cooler climates of the mountains. These two species are only found on the northern side of the valley, while another rare endemic species, themountain nyala (Tragelaphus buxtoni), is restricted to the southern side, and now survives at higher altitudes than its original habitat since the lower slopes are heavily farmed. More widespread mammals found here include themantled guereza (Colobus guereza), which is also threatened as its habitat disappears as does that of many other mammals of the highlands such asolive baboon (Papio anubis),Egyptian wolf (Canis lupaster),leopard (Panthera pardus),lion (Panthera leo),spotted hyena (Crocuta crocuta),caracal (Caracal caracal),serval (Leptailurus serval),common duiker (Sylvicapra grimmia), andgiant forest hog (Hylochoerus meinertzhageni). Birds includeRueppell's chat, the finchAnkober serin (Serinus ankoberensis),white-winged flufftail (Sarothrura ayresi), andblue-winged goose. The farmland is home to many butterflies, especiallyPapilio,Charaxinae,Pieridae, andLycaenidae.
There are several endemic animal species, one of which, theEthiopian wolf (Canis simensis), is critically endangered. Other endemics include thebig-headed mole-rat (Tachyoryctes macrocephalus) which is common on theSanetti Plateau in theBale Mountains. The mountain nyala finds its way up to the high moorlands although it is more common at lower elevations. Wintering birds includewigeon (Anas penelope),shoveler (Anas clypeata),ruff (Philomachus pugnax), andgreenshank (Tringa nebularia).
^Pfennig, Aaron; et al. (29 March 2023). "Evolutionary Genetics and Admixture in African Populations". Genome Biology and Evolution. 15 (4): evad054. doi:10.1093/gbe/evad054. OCLC 9817135458. PMC 10118306. PMID 36987563. S2CID 257803764.
^abMairal, M., Sanmartín, I., Herrero, A. et al. Geographic barriers and Pleistocene climate change shaped patterns of genetic variation in the Eastern Afromontane biodiversity hotspot. Sci Rep 7, 45749 (2017).https://doi.org/10.1038/srep45749
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