The Ruwenzori, also spelled Rwenzori and Rwenjura, are a range of mountains in eastern equatorial Africa, located on the border between Uganda and the Democratic Republic of the Congo. The highest peak of the Ruwenzori reaches 5,109 metres (16,762 ft), and the range's upper regions are permanently snow-capped and glaciated. Rivers fed by mountain streams form one of the sources of the Nile. Because of this, European explorers linked the Ruwenzori with the legendary Mountains of the Moon, claimed by the Greek scholar Ptolemy as the source of the Nile. Virunga National Park in eastern DR Congo and Rwenzori Mountains National Park in southwestern Uganda are located within the range.
The Ruwenzori are known for their vegetation, ranging from tropical rainforest through alpine meadows to snow. The range supports its own species and varieties of giant groundsel and giant lobelia and even has a 6 metres (20 ft) tall heather covered in moss that lives on one of its peaks. Most of the range is now a World Heritage Site and is covered jointly by Rwenzori Mountains National Park in southwestern Uganda and the Virunga National Park in the eastern Congo.
There is no water shortage in the Ruwenzori; yet, several members of the afro-alpine family resemble species that normally thrive in desert climates. The reason lies in their similar water economy. Water is not always readily available to the afroalpine plants when they need it. In addition, nightly frosts affect the sap transport in the plants and the intake of water by its roots. As the day begins, the air temperature and radiation level rise rapidly, putting strenuous demands on the exposed parts of the plants as they try to meet the transpiration demands of the leaves and maintain a proper water balance. To counter the effects of freezing, the afro-alpine plants have developed the insulation systems that give them such a striking appearance. These adaptations become more prominent as the elevation increases.
There are five overlapping vegetation zones in the Ruwenzori: the evergreen forest zone (up to 2,800 metres (9,200 ft)); the bamboo zone (2,800 to 3,300 metres (9,200 to 10,800 ft)); the heather zone (3,000 to 3,800 metres (9,800 to 12,500 ft)); the alpine zone (3,500 to 4,500 metres (11,500 to 14,800 ft)); and, the nival zone (4,400 to 5,000 metres (14,400 to 16,400 ft)). At higher elevations, some plants reach an unusually large size, such as lobelia and groundsels. The vegetation in the Ruwenzori is unique to equatorial alpine Africa.