The Aberdare (or Nyandarua) mountains are an isolated volcanic range that forms the easternmost wall of the Great Rift Valley, to the east of the high Kinangop/Laikipia plateau. They are around 100 km long from north to south (the northern end almost reaching the equator). There are two main peaks, Ol Donyo Lesatima (3,999 m) to the north and Kinangop (3, 906 m) to the south, separated by a long 'saddle' of land above 3,000 m. The small peak of Kipipiri (3, 349m) flanks the main range to the west, linked to it by a formerly forested valley at around 2,700 m.
Deep ravines cut through the forested eastern and western slopes and there are many clear streams and waterfalls. The park is renowned for its torrential waterfalls plunging from cloud-shrouded heights to spray-filled ravines. They include the magnificent Karuru falls, which drop 300m, the impressive Gura falls which torrent from the opposite side of the same Gorge, the drop of the Chania falls and the enchanting Gura falls which cascade across the yawning mouth of the Queen's Cave. Mist and rain occur throughout much of the year, with precipitation varying from around 1,000 mm on the drier north-western slopes to as much as 3,000 mm in the south-east. The vegetation varies with altitude. A rich alpine and sub-alpine flora, including species of Senecio spp, Lobelia spp, Erica spp, Helichrysum spp and tussock grasses, gives way at around 3,000 m to bamboo Arundinaria alpine and then montane rainforest (mainly Juniperus procerus-Podocarpus falcatus-Nuxia congesta forest on the western and northwestern slopes, ocotea forest on the south-east, and mixed Podocarpus latifolius forest on the east and on Kipipiri (Beentje 1990). Pockets of Hagenia forest occur in sheltered patches on the rolling moorland (Ojwang et al. 2006).
The National Park lies mainly above the tree line, with some forest and scrub at lower altitude in the salient near Nyeri. The Aberdares Forest Reserve (103,300 ha) occupies the lower slopes, in three main blocks that almost surround the Park, with Kipipiri Forest Reserve (5,100 ha) tacked on to the west. The southern boundary of the Aberdares Forest Reserve adjoins the Kikuyu Escarpment Forest. The Aberdares are an extremely important water catchment for the Tana River system, for the northern Ewaso Nyiro River and for Lake Naivasha, and provide much of the water supply for Nairobi and adjoining districts.
Wildlife in the area
The Aberdares hold 52 of Kenya's 67 Afro tropical Highlands' species The rare species include the Bongo (Tragelaphus euryceros) estimated at over 65 individuals in forest (KWS 2002), Leopard (Panthera pardus), Black Rhinoceros (Diceros bicornis), African Elephant (Loxodonta africana) (some 1,500 are resident:) and Giant Forest Hog (Hylochoerus meinertzhageni) and a population of Lions (Panthera leo), the African Golden Cat (Felis aurata), a rare species and Spotted Hyena (Crocuta Crocuta) (KWS 2005). Endemic small mammals include Aberdare Mole-shrew (Surdisorex norae) and Aberdare Mole rat (Tachyoryctes audax). The Montane viper (Vipera hindii) occurs only here and on Mt Kenya, and the Aberdares hold several amphibians that are endemic to the central Kenyan highlands, including Hyperolius montanus, Hyperolius cystocandieans, Rana wittei and Phrynobatrachus kinangopensis. The butterfly (Neptis kikuyuensis) is endemic to forests and on the Kikuyu Escarpment, and Charaxes nandina, endemic to central Kenya, has also been recorded (Larsen 1991).
The Range has six of the eight restricted range species in the Kenyan Mountains Endemic Bird Area. Over 200 species are recorded in all, including African Green Ibis, African Cuckoo Hawk, Mountain Buzzard, Jackson's and Moorland Francolins, Hartlaub's Turaco and Cape Eagle-Owl. The Scarlet-tufted Malachite Sunbird is found on the high peaks, foraging largely on lobelias, while other montane sunbirds (including Tacazze, Golden-winged, Malachite and Eastern Double-collared) are common at slightly lower altitudes. The restricted-range Aberdare Cisticola appears to be locally common in tussock moorland. Other vulnerable bird species found in the forest include Sharpe's Longclaw, Abbott's Starling, Aberdare Cisticola, Jackson's Francolin, Hunter's Cisticola, and Striped Flufftail (Bennun & Njoroge 1996).
Notable plants include the Aberdare endemics Lobelia deckenii sattimae and Helichrysum gloria-dei, and the Aberdare/Mt Kenya endemics Lobelia bambuseti, Senecio keniensis, Senecio johnstonii battiscombei var. battiscombei and Senecio keniodendron. The Aberdares are rich in the genus Alchemilla, including A. hageniae (endemic), A. argyrophylla (also on Mt Kenya), A. cyclophylla (also on Mt Kenya) and the rare A. microbetula (also on Mt. Elgon).
(iii), (vii) and (ix): Aberdares mountains present one of the most impressive landscapes of Eastern Africa, with its unusual vegetation, rugged terrain, streams and water falls (Karuru and Chania falls) that create an area of great scenic beauty. The high moorlands and diverse forests demonstrate exceptional ecological processes. The forest also has a rich history, freedom fighter Dedan Kimathi used as a post office, a giant tree where the Mau Mau would leave messages for Kimathi's attention. The Queen's Caves also found here were used by the Mau Mau (freedom fighters) to preserve their meat. The Aberdares were believed by the kikuyu to be one of the homes of Ngai (God) and originally known as Nyandarua "the drying hide" due to the distinctive fold of its silhouette.
The Aberdares is managed by the Kenya Wildlife service and Kenya Forest Service.
The Aberdare Mountains are one of Kenya's major water catchment areas, surrounded for the most part by intensive, small-scale agriculture. The high moorland is well protected and appears relatively safe, but habitat on the lower slopes has been severely damaged in recent years. Forest destruction and degradation is the major threat to the site, through agricultural encroachment, illegal Cannabis sativa gardens, poaching of valuable trees and forest grazing of livestock. Forest fires, either accidental or deliberately set (especially by honey collectors), have destroyed or damaged large tracts of forest during recent dry periods. Human-wildlife conflict has long been intense around the borders of the National Park salient and the forest reserves. Marauding animals regularly damage crops, and occasionally kill or injure people. On the moorland, the status of two of the threatened species - Sharpe's Longclaw and Aberdare Cisticola - remains little known, and needs investigation. The unusual vegetation, rugged terrain, streams and waterfalls combine to create an area of great scenic beauty in the National Park, which has tremendous potential for eco-tourism.
In Kenya the Aberdares can be compared to Mount Kenya as they are both areas of great scenic beauty and are important water catchment areas, both have afro-alpine flora, endemic plant species that are unique to these areas; that provide outstanding examples of ecological processes.
Virunga National Park in Congo can also be compared to Aberdares although they are slightly different in that the Ruwenzori Mountains are volcanic while the Aberdares formed due to tectonic movement during the formation of the Great Rift valley; both are areas of great exceptional beauty due to the unusual vegetation that is almost similar, rugged terrain, are important bird areas, have a rich concentration of wildlife i.e. elephants, buffalo, primates, among other animals all these make the areas, areas of outstanding universal value. The main difference is in the species composition the Aberdares has the eastern Arc species while the Virunga and Ruwenzori has central afro alpine vegetation and fauna influence by the vast Congo Basin.