Nyandarua Mountains

Description

The Nyandarua Mountains (also known by the colonial name of Aberdare Mountains or, simply, The Aberdares) is an isolated volcanic range that forms the easternmost wall of the Great Rift Valley, to the east of the high Kinangop/Laikipia plateau. The mountain range is around 100 km long from north to south (the northern end almost reaching the equator). There are two main peaks, Ol Donyo Lesatima (3999 m) to the north and Kinangop (3906 m) to the south, separated by a long 'saddle' of land above 3,000 m. The small peak of Kipipiri (3349 m) flanks the main range to the west, linked to it by a formerly forested valley at around 2700 m.

Deep ravines cut through the forested eastern and western slopes and there are many clear streams and waterfalls. The Aberdare National Park is part of the range’s ecosystem. 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 300 m, the impressive Gura falls which gush 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 Oldeania alpina and then montane rainforest (mainly Juniperus procera-Afrocarpus 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 pockets of Hagenia abyssinica forest occur in sheltered patches on the rolling moorland.

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 mountains 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.

Justification de la Valeur Universelle Exceptionnelle

The Nyandarua Mountains present one of the most impressive landscapes of Eastern Africa, with its unusual vegetation, rugged terrain, streams and waterfalls such as Karuru and Chania falls, which are of great scenic beauty. The high moorlands and diverse forests demonstrate exceptional ecological processes. The forest has four vegetation zones: sub-alpine vegetation, xeromorphic evergreen forest, montane humid forest, and submontane forest.

The site is both an Important Bird Area (IBA) and Key Biodiversity Area (KBA) as part of the East Afromontane hotspot. Its pristine head waters sustain pollution sensitive endemic macro-invertebrates, the Kenya jewel Platycpha amboniesis and the Maathai longleg dragonfly, Notogomphus maathaiea.  The forest also supports endemic birds, Aberdare cisticola and Abbott’s starling. The forest zones have over 63 endemic plant species. The forest also has a rich history; freedom fighter Dedan Kimathi used it as a post office, and there is a giant tree where the Mau freedom fighters would leave messages for Kimathi's attention. The Queen's Caves also found here were used by those freedom fighters to preserve their meat. The mountains are believed by the Gikuyu to be one of the homes of Ngai (God) and named them Nyandarua, meaning "the drying hide", due to the distinctive fold of their silhouette.

Criterion (vii): Nyandarua Mountains present one of the most impressive landscapes of Eastern Africa, rugged terrain, streams and waterfalls, for example, Karuru and Chania falls, which are of great scenic beauty. The mountains feature a sharp escarpment on the easternmost wall of the Great Rift Valley while their eastern side gently slopes into adjacent plains.

Criterion (ix): The mountain ecosystem supports important ecological processes within and beyond its catchment particularly the migratory marine shrimps and some fish species that breed in the mangroves and move to the fresh waters of the ecosystem-dependent Tana River.  Similarly, the Tana River mangabey and red colobus monkeys which are dependent on the gallery forest along the River also rely on the water and nutrients from the mountains.

Criterion (x): The forest zones have 63 endemic plants species which include Cissampelos friesiorum, Senecio margaritae, Adenocarpus mannii, Erica sylvatica, Lobelia deckenii, Helichrysum gloria-dei and Alchemilla johnstonii. The mountains are habitat to the site endemic musk shrew Surdisorex norae. The forest also supports endemic birds, such as the Aberdare cisticola and Abbott’s starling. It is also a habitat for national endemic macro-invertebrates, such as the Kenya jewel (Platycpha amboniesis) and the Maathai’s longleg dragonfly, Notogomphus maathaiea. 

Déclarations d’authenticité et/ou d’intégrité

The Nyandarua Mountains comprise 76,600 ha of National Park and 108,400 ha of a Forest Reserve protected by the Government of Kenya and managed by the Kenya Wildlife Service and the Kenya Forest Service, respectively. Currently the site is adequately protected and managed though there is anthropogenic pressure.

Comparaison avec d’autres biens similaires

The Nyandarua Mountains are comparable to Virunga which was inscribed on the World Heritage List under criteria vii, viii and x. Both mountains have similar patterns in species richness and endemism based on altitudinal gradients. The mountains are exceptional in terms of species diversity with over 63 site specific endemic plant species.

Like Mount Kenya National Park and Natural Forest World Heritage Property, the Nyandarua Mountains contain superlative natural beauty and aesthetic value. However, these mountains are different since they feature a sharp escarpment on the easternmost wall of the Great Rift Valley while their eastern side gently slopes into the adjacent plains. Mount Kenya, on the other hand, features a conical shape with steep slopes.