Based on physiography, the Himalayas can be broadly divided into two parts:the Western Himalaya, covering the Kumaon-Garhwal, northwest Kashmir, and northern Pakistan ; andthe Eastern Himalaya, which covers parts of Nepal, Bhutan, the northeast Indian states, Tibet, and northern Myanmar. Even though this division is based on some biological assumptions,the deep gorge created by the Kali Gandaki River between the Annapurna and Dhaulagiri mountains is a majordispersal barrier to many species, thereby making this a significant distinction.
The Western Himalayas
There is a general trend of decreasing moisture levels from the eastern part to the west of the himlayas because of the nature of the monsoon. This is coupled with the fact that the Western Himalayas are on an average higher than the eastern part. As a result, the Western Himalayas is drier and shows extremes of climate. This has shaped the biodiversity of the region.
The flora and fauna of the Himalayas shows a great diversity that changes with altitude. The lower elevations, which also form the outer Himalayas is covered by thebhabar, taraigrasslands and the siwalik ranges. These regions are more tropical in their nature .As one moves from the foothills to the higher elevations, the tropical forests merge into the temperate type. Thevegetation changes to oak, rhododendron, dwarf hill bamboo, followed by Alpine pastures up to the snow-line. The high altitude desert plateau of Ladakh is barren with sparse vegetation. Put together these form distinctly different habitats.
The animals found in these high altitude regions are well adapted to extreme temperature variation. Himalayan tahr, markhor and ibex are ungulates of the high altitude. Three species of wild sheep are found here: nayan, bharal and Urial. These sheep feed on the Alpine meadows and grassy mountain slopes. These ungulates form the prey base for the carnivores of the region. In the mid elevations , leopards and bears are the apex predators but in the higher elevations snow leopards and wolves rule.
The Western Himalayas has 11 species of birds restricted to it. The most prominent include the Himalayan quail, the cheer pheasant and the western tragopan.
A critical vegetation belt is formed by the Himalayan Subtropical Broadleaf Forests. This ecoregion represents the east-west-directed band of forests lying between 500 and 1,000 m. This eco region includes within it several forest types that change as one goes from east to west. Even though the forest types changes the role that it plays in the dynamics of the Himalayas is critical.It forms acrucil link in the chain of interconnected ecosystems that extend from the grasslands along the foothills to the high alpine meadows at the top of the world’s highest mountain range.
When winters are severe in the high altitudes, a number of species migrate to the lower reaches to beat the cold. This is true of many of the alpine species that move down to the coniferous forests in the southern part and move up to their homes in the Alpine region with the on set of summer. It is during this period that Subtropical Broadleaf Forests belt plays a critical role.
The National Park in this Zone are Dachigan, Khistwar and Hemis high altitude National Parks in Jammu and Kashmir, Great Himalayan and Pin Valley National Parks in Himachal Pradesh and Gangotri, Nanda Devi, GovindPashuVihar and Valley of flowers National Parks in Uttar Pradesh.
Grazing and trampling by large herds of domestic livestock, including cows, buffalos, horses, sheep, goats, and yak, are beginning to severely degrade the natural habitat. As livestock herds increase in number and size and exceed the carrying capacity in the lower habitats, pastoralists have begun to drive the herds into these alpine meadows, increasing the degradation threats here. An overnight campsite for pastoralists and their livestock as they migrate up and down the mountains can lay bare an area up to a hectare.
Overexploitation of rare medicinal herbs is another conservation threat in the area. Most of the collection sites are already under heavy grazing pressure, and the harvest of medicinal plants places additional stresses on this fragile ecosystem.
Adding to the localized degradation threats are several historical trade routes between India, Nepal, and Tibet that are still heavily used in this region. The accessibility brings with it associated degradation threats such as fuel wood collection and heavy use by people and pack animals. Because the ecoregion includes national borders, concentrations of defense personnel exploit its natural resources, especially timber and fuel wood.