Ecology of the Himalayas

The ecology of the Himalayas is incredibly diverse because of changes in climate, rainfall, altitude, and soil. At the bottom of the mountains, the climate is tropical, but as you go higher, it becomes very cold with permanent ice and snow at the top peaks. The amount of rain also changes, with more falling from west to east along the southern side of the mountains. Because of these different conditions, the Himalayas are home to many unique plants and animals, including the Nepal gray langur (Semnopithecus schistaceus). This variety makes the Himalayas an important place for studying how living things adapt to extreme environments.

Lowland forests

At the base of the Himalayas, on the Indo-Gangetic Plain, the plants and trees change from west to east depending on how much rain falls there. In Pakistan and Indian Punjab, there are dry Northwestern thorn scrub forests. Moving east, you find moist forests in Uttarakhand, Uttar Pradesh, Bihar, and West Bengal. These forests lose their leaves in dry seasons. Even more moist forests grow in Assam and the lower valleys of the Margalla hills.

The Terai belt

Indian rhinoceros in the Terai

Above the flat plains lies the Terai strip, a wet and marshy area with sand and clay soils. This area gets more rain than the plains below, and rivers from the Himalayas slow down here, spreading rich soil during the rainy season before drying up later. Because of this, the Terai has a lot of groundwater. In the middle of the Terai, you can find the Terai-Duar savanna and grasslands. This area has a mix of grasses, open woodlands, and forests, and it is home to some of the tallest grasslands in the world. These grasslands are also where the Indian rhinoceros lives.

Bhabhar belt

Above the Terai belt is an upland zone called the Bhabhar. This area has porous and rocky soil made from debris washed down from higher mountain ranges. It lies at the foot of the Himalayas where streams flow down to the plains. The Bhabhar and lower Shiwalik ranges have a warm climate.

The Himalayan subtropical pine forests are found at the western end of this warm belt, with forests mainly made up of Chir Pine (Pinus roxburghii). In the central part of the range, you can find the Himalayan subtropical broadleaf forests, which have many types of forests. One kind of forest is mainly made up of the sal tree (Shorea robusta).

Siwalik Hills

The Siwalik Hills, also known as the Churia or Margalla Hills, are a range of lower mountains that stretch across Pakistan, India, Nepal, and Bhutan. These hills usually rise between 1,500 to 2,000 meters high. The southern slopes are steep because of a fault line called the Himalayan Frontal Thrust, while the northern slopes are gentler. The rocks in this area let rainwater soak down into lower regions, which means only small, scrubby forests grow on the hills. The warm, moist forests typical of lower tropical areas continue here.

Inner Terai or Dun Valleys

The Inner Terai valleys are open spaces north of the Shiwalik Hills or tucked between the Shiwalik subranges. Examples include Dehra Dun in India and Chitwan in Nepal. In these areas, you can find Himalayan subtropical moist broadleaf forests growing naturally.

Lesser Himalaya

The Lesser Himalaya, also called the Mahabharat Range, is a tall mountain range that rises between 2,000 and 3,000 meters high. It has steep sides on the south and gentler slopes on the north. Rivers cut through the range, creating deep valleys.

Himalayas from Kullu Valley, Himachal Pradesh.

In these middle heights, warm forests change into cooler forests made of different kinds of trees. West of the Kali Gandaki River, you find the western Himalayan broadleaf forests, stretching from the Kashmir Valley through Himachal Pradesh and Uttarakhand, and into western Nepal. To the east, the eastern Himalayan broadleaf forests grow across eastern Nepal, through Sikkim and Bhutan, reaching into much of Arunachal Pradesh.

Midlands

This hilly area, called Pahad, sits about 1,000 meters (3,300 ft) above sea level and gently rises to around 4,000 meters (13,000 ft) over a distance of 100 kilometers (62 mi). This rise happens near a special fault line called the Main Central Thrust, where the Greater Himalaya mountains begin.

Subalpine forest at Cher-tang La, Bhutan

Above the broadleaf forests, between 3,000 and 4,000 meters (9,800 and 13,100 ft), you can find cool, coniferous forests split by the Gandaki River. Different types of these forests grow in various places, such as northern Pakistan, Jammu and Kashmir, Himachal Pradesh, Uttarakhand, western Nepal, eastern Nepal, Sikkim, Bhutan, and Arunachal Pradesh. Important trees in these forests include East Himalayan Fir, West Himalayan Spruce, and Himalayan Hemlock. There are many kinds of Rhododendrons here, especially in the northeastern Himalayan area, with over 60 different species.

Greater Himalaya

The highest parts of the Himalayas rise sharply to over 4,000 meters (13,000 ft), where snow and ice never melt. As you move from east to west, the mountain system grows wider, and more high mountain ranges appear. For example, the Kagmara and Kanjiroba ranges both climb above 6,000 meters (20,000 ft) north of the Dhaulagiri Himalaya in central Nepal.

Above the trees, you find alpine tundra. This area has short plants, grasses on steep slopes, and meadows with soft plants. Different parts of the Himalayas have their own special shrubs and flowers. In the west, near Pakistan, Jammu and Kashmir, and Himachal Pradesh, you can find unique shrubs and flowers. To the east, along the border with Tibet, Uttarakhand, Nepal, Sikkim, Bhutan, and Arunachal Pradesh, there are more flowers and plants, including junipers and rhododendrons. The Valley of Flowers National Park has over 520 types of plants, many of which bloom beautifully. These high grasslands are where the endangered snow leopard lives during the summer.

Trans-Himalaya

The area between rivers that flow south into the Ganges or Indus and rivers that flow north into the Brahmaputra or mainstem Indus often has lower, less rugged mountains. These south-flowing rivers create valleys that are sometimes dry because they are protected from rain. Some of the highest permanent villages on Earth are found on the slopes of these valleys.

Ecoregions

The Himalayas and the areas around them have many different natural environments, called ecoregions. These include places like alpine meadows, conifer forests, broadleaf forests, and savannas.

The ecoregions are: