item




BIODIVERSITY AND ECOLOGY OF THE HIMALAYA


Published on: 12/23/2020 4:05:59 AM

The Himalaya & Adjacent hill ranges in north-eastern India represent a complex array of physical & geo-political environment, well known for geo-hydrological, biological, aesthetic & cultural values. The region, collectively referred to as Indian Himalaya Region (IHR), encompasses a series of lofty ranges many of which exceed 7000 m above sea level, alpine meadows, lake basins, cold desert, inter-montane valleys, deep gorges, snowfields, glaciers & alluvial plains.

Although the Main Himalaya and the hills of North-eastern states have a number of similarities in their physiography & ecology, they differ inherently in terms of origin and evolution. The former ranges, geologically young and tectonically active. On the other hand, the Khasi, Jaintia and Patkai ranges of North eastern Hill Region (NEHR) are of ancient origin.

Biodiversity of Himalaya

Owing to a Unique biogeographic location i.e., at the junction of pale arctic & Indo - Malayan Realm, wide altitudinal range, topographic variation & numerous habitats, the IHR harbours a rich array of flora & fauna. The region as a whole, and NEHR in particular, is regarded as one of the global biodiversity hotspots.

Flora

Traditionally, the IHR has been recognized as distinct phytogeographic zone with two sub divisions viz., western Himalaya (WH) and eastern Himalaya (EH), There are approximately 10,000 species of vascular plants in the IHR, that forms more than 50% of the Indian Flora. Of these, about 3,160 species are endemic or near-endemic. Most dominant families of flowering plants in the IHR include Orchidaceae, Asteraceae, Poaceae and Fabaceae. It is estimated that there may be about 13,000 species of fungi and around 1,100 species of lichens in the IHR.

Based on the distribution of rare endemic and threatened species, several localities have been identified as important areas for plant conservation. These are Drass & Surru valley (Ladakh); Kishenganga, Liddar valley, Bhaderwah (Kashmir); Dhauladhar, Bushahar, Narkanda & churdhar (HP); chakrata, valley of flowers, Nandhaur valley, Didihat, Sandev and Gori valley (UK); Tista valley, Zemu, Pangolakha, Singalila (Sikkim); Neora valley (WB); Tirap, Hohit, Kamlang, Abor and Mishmi hillls (AP); Khasi, Jaintia Hills (Meghalaya); Blue Mountains & Patkai hills (Mizoram & Nagaland).

Fauna

Over 240 Mammal species have been described across the IHR, of which 12 are endemic. The endemic includes the golden langur, the hispid hare, pigmy hog, Asiatic wild dogs, sloth bear, gaur and several species of deer, such as Muntjac and sambar, snow leopard, black bear, blue sheep, takin, argali and Himalayan Thar etc.

Around 750 bird species are recorded from across the region, with 20 endemics. S/a babblers, wren babblers, Himalayan quail, cheer pheasant, western tragopan, rusty throated wren babbler, snowy - throated babbler, chestnut-breasted partridge, rufous – throated wren babbler, white - throated tit, Orange bullfinch, black - necked crane etc. There are 29 reptiles and 35 amphibian’s endemics to Himalaya. some are Agama tuberculta, Laudakia Himalaya, Coluber rhodorachis There are approx. 270 species of fishes in IHR in which 33 species are endemic. Some are Minnows, carps, river loaches, sisorid catfish, Ladakh snow trout, Golden masheer etc.

Ecosystem Services & Diversity

The abrupt rise of the Mountains from less than 500 mtr. to over 8000 mtr. results in a diversity of ecosystem that range from sub-tropical to alpine & arid types. The complexity of topography, geology and relief features coupled with intensive biotic influence, have given rise to a variety of ecosystems. The major Ecosystems are: 

1. The Forest Ecosystem

Wide elevational rainfall and topographic gradients in the IHR have given rise to various forest formations. The subtropical belt (below 1000 m) is represented by the evergreen & moist deciduous forests, woodland and savannah. characteristic species in the Terai - Bhabar tract is Sal and in the NEHR other dipterocorps (s/a Dipterocarpus retusus, shorea assamica etc) Adjacent and to the north of the subtropical forest is a band of subtropical pine forest dominated by chir pine in outer Himalaya and Khasi pine in Meghalaya.

Temperate humid forests, equivalent to 'cloud forests', thrive at elevations of (Eastern Himalaya) where moisture tends to condence and remain in the air during the warm, Moist growing season. These forests are dominated by evergreen broadleaf trees s/a Oaks. The cloud forest in the east is rich in epiphytes, represented by several dicotyledons and variety of Mosses, ferns and orchids, and provide rich nesting habitat for many bird species.

Dwarf Bamboos in the under-story form food for the charismatic red panda. The temperate forests in the (Western Himalaya) are Much more open and drier dominated by conifers s/a chirpine and a few oaks. At higher altitudes there are extensive areas under blue pine, chilgoza pine, silver fir and spruce.

The North-Eastern region has the most diverse types of forest ecosystem in the country. The forest cover of the region is more than three times higher than the national average. Per capita forest cover in north east region (0.52ha) is much higher than the national average (0.076ha).

2. The cold Deserts (Alpine Arid Ecosystem)

The rain shadow areas north of Great Himalayan range especially in much of Ladakh, Lahul and spiti, inner ranges of Uttarakhand (Nilang, Malari, Lapthal, Upper Johar, upper Byans) and a small portion of Sikkim plateau represent this ecosystem. The characteristic features of this ecosystem are sparse vegetation cover (<15%), low primary productivity and extreme aridity. Major vegetation formations in this area are scrub steppe. A few patches close to the valley bottoms with moist clayey soil support herbaceous communities.

A considerable area falls under typical desertic formation with less than 5% vegetation cover characterized by scree slopes, very high altitude (>4800 m) pioneer environments and other rocky slopes dotted with mosses, lichens and a few hardy plants s/a species of stipa, Melica, christolea, sedum, Draba and saussurea.

3. Alpine Meadows of the Greater Himalaya

The alpine zone in the Himalaya is separated by a distinct treeline (3500+200 m in the western and 4000+200 m in the eastern Himalaya). This is the zone of tree less vegetation with highly specialized growth forms. The major vegetation types in the alpine zone include alpine scrub, alpine herbaceous formations locally k/a Bugyal (UK), Kanda or Thach (HP) and Marg (Kashmir). The alpine arid areas and alpine meadows of the Greater Himalaya have been traditionally used by a large number of local and migratory pastoral communities as summer grazing ground. Hence, they have frequently been described as 'Alpine Rangelands'.

4. Grassland Ecosystem

Most of the grasslands in the temperate, sub-tropical and tropical belts in the IHR are anthropogenic in nature i.e., derived as a result of frequent fire and forest clearing. The alluvial Grasslands along the foothill valleys are among the tallest in the world. Major tree is Trewia nudiflora, Dalbergia sissoo etc. In the bhabar tracts the grasslands are called 'chaurs' which support a large number of wild herbivores. The temperate grassy slopes, locally called 'Ghasnis' in HP and Uttarakhand are Managed by the local communities for hay production.

5. The Riverine Ecosystem

The drainage system in the IHR can be broadly grouped into three Main river systems viz, the Indus, the Ganges and the Brahmaputra. The average annual flow in the three river basins in Indian territory alone is estimated at 1009 Milliard m3. The Major drainage system of the WH is Indus, Jhelum, Chenab, Ravi, Satluj, Ganges, Yamuna and Sharda. While in the EH Major river system include Tista, Brahmaputra system and Irrawaddy. The riverine ecosystem is of considerable ecological and conservation interest as they support a diverse array of flora and fauna besides serving as lifeline for human societies along their basins.

6. The Wetland

The Margins of shallow lakes, river courses and man-made water bodies in this region represent the wetland ecosystems. Many of the high-altitude wetlands serve as breeding grounds of Migratory birds during summer months. The wetlands also support a highly productive and dynamic ecosystem. One the basis of their origin the Himalayan Lakes can be classified into four groups - (i) Glacial lakes which are formed in and around glaciers; (ii) structural lakes, formed by folds & faults (Nainital lake in UK (iii) Natural Dammed lake - gohna Tal in Garhwal, UK (iv) Remnant lake, which were originally structural but represet the remnants of vast lakes (Tso Moriri, Tsokar, pongong Tso, Dal lake). It is estimated that there are over 2000 small or large wetlands in the IHR, including reservoirs, tanks, lakes, seasonal swamps & other categories.

7. Agro - ecosystem

Agriculture and animal husbandry have been age old land use practices in the IHR. A considerable area in the WH is under settled agriculture (terrace farming). Traditional millets, cereals and pulses along with horticultural crops have become a major source of revenue. In the NEHR shifting cultivation or slash and burn agriculture, locally known as Jhum, is the main form of agriculture. The Jhum cultivation involves clearing of vegetation and then slashing and burning of the plant parts including Debris. There are four categories of Jhums in NEHR -

(i) Traditional Jhum: Practiced in the interior areas where human population has not increased much. This is generally sustainable but may not fullfill all the needs and aspirations of a modern livelihood major areas are buffer zone of Nokrek Biosphere Reserve, Garohills, Meghalaya and in Nongching village of Nagaland.

(ii) Distorted Jhum: As population increases, the villagers are forced to reduce the fallow period in order to allot Jhum land to newly married couples. This type of Jhum is neither productive nor sustainable. Examples: Many parts of Mizoram, Parts of A.P, Manipur hills and in west khasi hills of Meghalaya.

(iii) Improvised Jhum: This includes recently adapted cultivation of cash crops in Jhum fields, e.g., green peas in pomlakarai, Meghalaya and indigenous kolar beans (Rajma) in high altitude villages of Nagaland where rice cannot be grown.

(iv) Modified Jhum: During past two decade two externally funded development projects were implemented in Nagaland, Meghalaya, Manipur and hill districts of Assam. Each of these projects had a major component on improvement of Jhum. s/a improving the livelihoods through promotion of tree husbandry and cash crops, institution building & microfinance. Jhum Cultivation has not only been the main source of livelihood for most of the hill - tribes in NEHR, this practice has also played a critical role in conserving Agri-biodiversity and Traditional knowledge system (TKS).

Also Read | PHYSICAL DIVISIONS OF THE INDIAN SUBCONTINENT