is the study of the geographical distribution of plants and animals.
Most species of plants and animals of the world are essentially restricted
in their distribution either by (natural) barriers of some description
or because of the history of their origins and dispersal. The major
units of distribution are referred to as bio-geographical regions, which
are largely defined by the past and present relations of the continents
to each other. These major global units of bio-geography were first
recognised by P.L.Sclater (1858, in J. Proc. of Linn. Soc.2), and later
elaborated upon and described in modern terms as "realms" by P.J.Darlington
(1957,in Zoogeography. John Wiley & Son. New York).
Biological regions or "Bio-geographical Realms" are defined by climate,
altitude and terrain (geography) which have acted upon the evolutionary
process to give rise to certain distinctive life forms. Bio-geography,
therefore, refers to this specific and distinctive community of plants
and animals (biological community) occupying a specific geographical
region. Each region is then subdivided into faunal or vegetational zones
depending on the criteria used.
major bio-geographical regions (realms) have been recognised and these
1. Ethiopian - Africa except NW corner and parts of southern Arabia
2. Oriental - Tropical Asia & associated continental islands.
3. Palaearctic - Eurasia above the tropics and NW Africa
Nearctic - North America except Mexican tropics
Neotropic - South & Central America & Mexican tropics
6. Australian - Australia with New Guinea & islands.
The Indian sub-continent occupies a unique position in the Bio-geographical
realm of the region. Broadly falling within the Oriental Region of tropical
Asia, the Indian sub-region absorbs the Palaearctic Region in the NW
Himalayas. The Indo-Chinese sub-region in NE India, together with Andaman
island group, forms a part of the Indo-Malayan realm. In the south,
the Deccan plateau along with Sri Lanka absorbs the Ethiopian realm.
Biogeographic zones: With the mighty Himalayas forming the northern
boundary, the Indian territory is confined within natural features that
delineate the sub-continent as a whole. Within this bio-geographical
synthesis there is yet another division of bio-geographic sub-regions
which are further restricted to bio-climatic and vegetation zones each
supporting its own characteristic animal and plant life. The two main
Indian bio-geographic sub-regions are the Himalayan sub-region and the
Indian Peninsular sub-region and within these are the several zones
(Trans Himalayan; West & East Himalayan; North East Inida; Indian Desert;
Indo-Gangetic plains; Western & Eastern Ghats; Deccan Plateau; Coasts
1. Himalayan sub-region : The Himalayan sub-region comprises of the
Trans-Himalayan plateau and the western & eastern mountain zones and
because of the varied vegetation, climatic conditions and altitudinal
ranges, each harbours its own assemblage of animal and plant communities.
The Trans-Himalayan plateau at an average
altitude of 4500 m consists of the eastern part of Ladakh. It is a windswept
region of scanty rainfall, high radiation and intense cold. This is
the only region in the world where both desert and arctic conditions
prevail. The plants and animals in this area are highly adapted to such
habitat is defined by perennially snow-cladpeaks, seasonal marshlands
and high-altitude lakes. Except for meandering rivers such as the Indus,
most of the marshes and lakes are brackish due to high evaporation regimes.
This seemingly inhospitable terrain nevertheless hosts a variety of
flora and fauna. The vegetation is dominated by Tibetan Gorse (Caragana
sp) on the hill slopes. Marmots, Woolly hare, Tibetan antelope, Tibetan
Sheep, Bharal, Wild Yak, Wild Ass, wolf and snow leopard are some of
the typical denizens of this zone.
& East Himalayan: South of the Trans-Himalayan plateau and sharply
demarcated by the tree-line is the forested area stretching form west
to east Himalayas. This is marked by variations in forest types determined
by rainfall regime, altitude and latitude.
In the west Himalayas this zone is dotted with grassy meadows covered
with Alpine and sub-Alpine vegetation in Kashmir and the higher reaches
of Garhwal. Both floral and faunal elements are influenced by Palaearctic
types. The Kashmir Stag, Ibex, Markhor and Urial are some of the examples
of the western Palaearctic influence.
of Nepal the vegetation in this zone gives way to a contrasting mix
of moist to wet-evergreens typical of the east Himalayas.
true tropical dense forests of the North East start from the lower hills and valleys, also known as "Dun" and "Terai",
reaching up to 3000m. This zone is best known for the variety of Indian
fauna & flora. Tiger, Elephant, leopard, gaur, sambar, chital, hog deer,
swamp deer, buffalo, rhinoceros and many other smaller mammals are found
in this belt. Here the faunal element is a mix of Indo-Chinese, Indo-Malayan
2. Indian Peninsular sub-region.
area from the base of the Himalayas to the tip of the peninsula and
comprising of Indus-Ganges-Brahmaputra river basins, the entire Deccan
plateau, and the Western/Eastern Ghats with adjacent coasts, forms the
proper Indian peninsular sub-region. Here the Arid tracts of Rajasthan and northern Gujarat host the elements of the great
desert that once stretched from Indus valley all the way to Baluchistan
and Iran. The rich alluvial Gangetic Belt with Sal dominated terai forests continue eastwards
merging with forested floodplains of Brahmaputra, as both river systems
join up to nurture the vast mangrove forests of the Sunderbans.
triangular Deccan plateau is the
true home of Indian mammals, represented by the Spotted deer, Nilgai,
Blackbuck, Four-horned antelope and the Sloth bear - found nowhere else
in the world. The west-east sloping plateau is dominated by moist deciduous
forests of Vindhya and Satpura ranges in the north, bounded by the Western
and the Eastern Ghats on either flank and the rest characterised by
open stony dry scrub interspersed by innumerable rain-fed waterbodies.
Two major rivers originating from the Vindhyas, the Narmada and the
Tapti flow westwards while three major rivers originating from the Western
Ghats, the Krishna, the Godavari and the Kaveri flow eastwards.
The Desert Region occurs in the extreme
west, in Rajasthan and northwestern parts of Gujarat, extending towards
Sind, Punjab and Baluchistan. This is the home of the desert cat, the
desert fox, the desert hare and several species of gerbilles. The area
also forms the home range of the Great Indian Bustard, the Houbara Bustard
and the Florican.
The Coasts Areas of the peninsula
are dominated by the Western Ghats and Eastern Ghats. The Western Ghats stretching from the Surat Dangs in the north to almost
the tip of the peninsula, receive heavy rainfall during the South West
monsoon. The vegetation is tropical wet evergreen characterised by tall
trees, dense undergrowth, bamboos, sholas and grasslands on the higher
elevation and semi-evergreen lowland forests, secondary growth and mangrove
stands all along the coastal belt. Major faunal elements are represented
here, including tiger, leopard, smaller cats, Gaur, Sambar, spotted
deer, Giant squirrels and the unique Nilgiri tahr. The endemic species
include, the Lion-tailed macaque, the Nilgiri langur, the Malabar civet,
the Brown mongoose, the Stripenecked mongoose and the spiny mouse. Over
500 species of birds occur here of which the Black-and-orange flycatcher
and the Nilgiri wood pigeon are endemic.
offshore Islands of the Andaman
and Nicobar group in the Bay of Bengal represent the Indo-Malayan elements.
Among the endemics here, the Narcondam hornbill, confined to one small
outlying island of the group, has a total population of only about 400
by S. A. Hussain