10 Biogeographical Classification of India

Saleha Jamal

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Structure

 

1.1 Introduction : Definition, Nature and Scope

 

1.2 Types of Biogeography

 

1.3 History of Biogeography

 

1.4 Biogeographical Regions : Meaning and Concept

 

1.5 Biogeographical Classification of World

 

1.6 Biogeographical Classification of India

 

 

1.1 Introduction: Definition, Nature and Scope

 

The earth consists of variety of life for fulfilling the need of man over thousands of years. This diversity of living creatures on earth forms a support system that has been used by civilizations for their growth and development. Attempts have been made by various scholars in order to categories and classify the variety of life given by nature over a century and this has led to the division of its organization into plants and animals. This information on the nature’s diversity has helped man in utilizing the earth’s biological wealth for the benefit of humanity and is very necessary for the process of development (Roy, 2016). Thus it can be said that biogeography simply means the study of organism (fossil or living) of the earth to the areas they occupy. In other words biogeography may be defined as “one of the aspects of geography which deals with the correlation among the animals, plants and their geography”. Biogeography as a subject is interdisciplinary and its subject matter deals with the distribution of organisms and communities in time and space. The primary goal of a biogeographer is to present a vivid picture of spatial patterns of distribution of plants and animals, the temporal and spatial variations and processes and causes thereof. The basic spatial unit for biogeographical studies is the biosphere or part thereof. The biosphere is the largest ecosystem and it is segmented into numerous ecosystems according to objectives of the study and spatial scale such as mountain ecosystem, crop ecosystem, delta ecosystem, grassland ecosystem etc (Singh, 2010).

 

Later the subject matter of biogeography further bifurcated into two separate branches of phytogeography (the distribution of plants) and zoogeography (the distribution of animals). In biogeography much emphasis is given to the study of phytogeography because the distributional pattern of plants becomes easy to study due to their static nature and their aggregation in static community while on the other hand animals are dynamic and they move from one place to another with very high variability in their behavior. Some believes that biogeography is a part of physical geography as it often related to the examination of physical environment and how it affects species and shaped their distribution across space.

 

1.2 Types of Biogeography

 

Today biogeography is broken into three main fields of Historical biogeography, Ecological biogeography and Conservation biogeography.

 

Historical biogeography is also known as paleo-biogeography and studies the past distribution of species. It looks at their evolutionary history and things like past climate change to explain why a certain species may have developed in a particular area. It also deals with species dispersal, distribution and extinction of species of plants and animals through geological period.

 

Ecological biogeography looks at the current factors responsible for the distribution of plants and animals and it emphasize upon three things. Firstly; climatic equability which deals with the factors as diurnal and annual range of temperature because it is harder to survive in the areas of extreme climate and extreme fluctuation in temperature. Secondly; primary productivity which deals with the evapotranspiration rate of plants because areas having  high  rate  of  evapotranspiration  will  have  high  plant  growth  and  vice  versa. Thirdly; habitat heterogeneity which deals with the variations in the habitat of organisms.

 

Conservation biogeography deals with the protection and conservation and restoration of nature and its flora and fauna. Both the methods of on-site conservation and off-site conservation of species are given due consideration (Singh, 2010; Briney, 2017).

 

1.3 History of Biogeography

 

The history of biogeography is as old as the appearance of small organism on surface of the earth including terrestrial or marine environment. The work of palaeogeographers, palaeobotanist, palaeoecology, historical geomorphologist has played an important role in contributing to the basic subject matter of ancient biogeography. During the ancient times the distribution of flora and fauna was not like as it is today. This part of historical biogeography dealt with the great mammoth, dinosaurs and giant trees which lived on the surface of the earth nearly 200 million years ago. The medieval period starts approximately from 4000 years BC to the workers of the period of 16th century. 15th to 16th was called as early modern era in the medieval history of biogeography because in this period biogeography got its independent identity like that of chemistry, physics and geography. The period from 17th century to present date is called as the period of modern age (Chouhan, 2013). The geographical voyages of discoveries in the 18th century paved the way for the rise of biogeography as a science in its own right. Biogeography as a subject started to receive much attention in the 19th century because one of the first modern delimitations of biogeographic regions was created in 1858 by the English ornithologist Philip L. Sclater, who based his division of the terrestrial world on the distributions of birds. In 1870, the biologist Adolf Engler devised a scheme based on plant distribution. Darwin’s theory on origin of species was largely based on the emerging biogeographic understanding of the era in which Sir Joseph Dalton Hooker a plant collector and systematist and Alfred Russel Wallace a zoogeographer greatly influenced Darwin. Darwin collected and pondered the biogeographical material that ultimately leads him to the concept of evolution by natural selection (Cox and Moore, 2006; Groves, 2016). The next significant advancement in biogeography took place in 1915 when William Diller Matthew a geologist and paleontologist said that ‘at any given time period, the most advance and progressive species of the race will be those inhabiting that region and the most primitive and unprogressive species will be those remote from this center’. In 1920s and 1930s a new development took place which combined the rapidly evolving field of ecology with biogeography. In recent times a significant portion of the theoretical literature on biogeography has been devoted to argument about the efficacy of vicarianism compared to dispersalism.

 

1.4 Biogeographical Regions: Meaning and Concept

 

Biogeographical regions are those regions which show the regional pattern of distribution of world’s flora and fauna at continental scale. The biogeographical regions are identified, determined and represented on the map on the basis of some common characteristics that are held by plants and animals. In a broad and fundamental sense a biogeographical region may be described as an area possessing a particular set of climatic conditions i.e., its own distinctive temperature and rainfall regime and its own diurnal and seasonal changes which give rise to a particular kind of vegetation which in turn give rise to a particular kind of animal life. The biogeographical regions with respect to plant and animal are studied separately such as floral regions and faunal regions because both vary in their characteristics as it has already been mentioned above.

 

1.5 Biogeographical Classification of World

 

It was Adolf Engler a German botanist who was the first person to identify the world floral regions in the year 1879. He divided the world flora into four major regions on the basis of evolutionary history and dominant characteristics of plants and depicted them on map. These regions were the northern extratropical realm, the palaeotropical realm, the South American Realm and old ocean realm. Then R. Good and (1947) and A. Takhtijan (1986) presented the scheme and divided the world flora into six major floral regions. These regions were Neotropical, palaeotropical, Holarctic, Australian, cape floral and Antarctic.

 

With respect to the division of faunal regions the early attempt was made by J. Prichard (1826) and W. Swinson (1844) who divided the world fauna into six major regions of North American region, European region, Asian Region, South American Region, African Region and Australian region. Then Philip Sclater (1858) and Alfred Russel (1876) again divided the world fauna into six region namely; Palaearctic region, Nearctic region, Oriental region, African region, Australian region and Neoarctic region (Singh, 2010).

 

For proper understanding and explanation the land plant species of the world are grouped into six major floristic regions on the basis of their worldwide distribution which are as follows:

 

1. Australian Floral Region: Faunists and florists agree that Australian continent as a whole is a district biogeographical entity and it is ranked as a region. Thus, this region includes the plant of whole Australia which is characterized by typical plant species.

 

2. Cape Floral Region: This floral kingdom has developed in the southern tip of Africa where the plants having bulbs and tubers have developed and these represents the typical plant species of the floral kingdom.

 

3. Antarctic Floral Regions: this region includes a narrow strip in the north of Antarctica which runs from Patagonia and Southern Chile of South America.

 

   4. Palaeotropical Floral Region: this region includes most of Africa, South West Asia, South Asia, South East Asia and southern and middle portions of China. This region is further subdivided into African sub-kingdom, Indo-Malaysian sub-kingdom and Polynesian sub-kingdom.

 

5. Neotropical Floral Region: this region includes the whole of South America except southern Chile and Patagonia.

 

6. Boreal Floral Region: this floral region includes the whole of Northern America except

 

Middle America, Greenland, entire Europe, Northern Asia and Arctic Region.

 

There are numerous Biogeographers who have divided the world into faunal regions but faunal region as represented by A.R. Wallace is the most convincing and acceptable among all the subsequent division which is as follows.

 

1. Palaearctic Faunal Region: this region includes Europe and middle and north Asia. This region is further divided into five regions namely; tundra region, temperate coniferous forest region, temperate grassland region, deciduous forest region and desert region.

 

2. Nearctic Faunal Region: this region consists of the geographical territories of North America and Greenland. It is important to find out that there is much similarity between Palaearctic and Nearctic faunal regions. Both the regions were connected through the Bering land bridge during tertiary period which enables them to free exchange and migration of animals.

 

3. Oriental Faunal Region: this includes the geographical areas of mainly south and south-east Asia. The Himalayas, Tibetan plateau and Chinese mountainous region form a transitional zone between Palaearctic and Oriental faunal regions. The whole of this faunal region comes under tropical region and hence associated with the Ethiopian faunal region.

 

4. Ethiopian Faunal Region: this region incorporates substantial areas of the whole of Africa south of Sahara and far off south western Arabia which is separated from the African region by Red Sea. This region is subdivided into three types namely; desert region, savanna region and tropical forest region.

 

5. Australian Faunal Region: this region includes Australia, New Zealand and islands between south-east Asia and Australia such as New Guinea, Solomon and Samoa etc.

 

6.  Neoarctic Faunal Region: this region includes the whole of South America characterized by tropical environment. This region is further sub divided into three types namely; temperate grassland region, desert region and tropical forest region.

 

 

1.6 Biogeographical Classification of India

 

The Indian subcontinent is a part of vast Oriental biogeographic regions and is very rich in biodiversity. Being a physical part of Asia, India is least limited by geographical barriers, thus it has acted as a center of dispersal of species as well as has received species from the Palaearctic, Ethiopian, Indo-Chinese and Indo-Malayan sub regions. The biogeographical classification of India has been attempted by various earlier scholars (Hooker 1854, Clarke 1898, Chatterjee 1940, Puri 1960, Rodgers and Panwar 1988). In the opinion of Rogers and Panwar the Indian region can be divided into 10 biogeographical regions which are as follows and shown in Fig. 1. The biogeographic zones are divide into secondary units called as biotic province (Table 1) for example, the biogeographic zone Gangetic Plain is divided into two biotic provinces namely, Upper Gangetic Plain and Lower Gangetic Plain. The reason behind showing the biotic province under the present work is because sometimes barrier to animal dispersal such as major river valleys may lead to the evolution of distinctive species element in different biotic provinces.

 

1. Trans-Himalayan Region: the Himalayan range immediately north of the Great Himalayas is called as Trans Himalayas. This region is represented by the cold desert of Ladakh, Jammu and Kashmir, North Sikkim and Luhil-Spiti areas of Himachal Pradesh. This region consists of Karakoram, Ladakh, Zaskar and Kailash mountain ranges. It constitutes 5.6 per cent of the total geographical area and estimated to cover 186200 km2 in India. The vegetation is primarily of dry alpine scrub formation. The genera that contribute to the sparse vegetation are Saxifraga, Draba, Ephedra, Kobresia and Carex. This region is the favorable habitat for the biggest population of wild sheep and goat and other rare fauna found here are Snow Leopard and migratory Black-necked Crane. This region represents an extremely fragile ecosystem.

 

2. Himalayan Region: this region constitutes 6.4 per cent of the total geographical area including some highest peaks in the world (Fig. 2). This region extends from east to west upto 2400 kms from Kashmir to Arunachal Pradesh and supports a remarkable assemblage of vegetation formation. As far as plants are considered this region consists of more than 8000 species of flowering plants of which 50 per cent plant species are endemic. The subtropical and temperate zone in the West Himalaya is predominated by tall conifers and broad-leaved species dominate in east Himalaya. Oaks are common in West Himalaya and show a distinct altitudinal distribution. The slope of East Himalaya is characterized by the presence of more than 85 species of colored rhododendrons, bamboos and variety of orchid species. This region is characterized by endangered species of bovid such as Bharal, Ibex, Markhor, Takin and others are Hungul and Musk Dear.

 

3. Indian Desert Region: this region occupies 6.8 per cent of the land surface (Fig. 2). This region lies mostly in the Rajasthan state of India and extended into some parts of Haryana, Punjab and Gujarat. The desert region extends from the Aravalli hills in the north-east to the Rann of Kutch along the coast and the alluvial plains of the Indus River in the west and north-west. The desert is also characterized by hillocks and sandy gravel plains this is the reason why, this region have diversified habitat and ecosystem. The vegetation, human culture and animal in this region are very rich in comparison with other deserts of the world. The plant/tree species which are found here are Acacia, Tecomella, Prosopis Cameraria. Bushes of Ziziphus, Capparis deciduas and Calligonum polygonoides are also common. This region also supports some endangered species of mammals such as Wolf, Caracal, Desert Cat, Chinkara, Blackbuck, Chosingha, Nilgai and Gazelle. Birds like Houbara Bustard and Great Indian Bustard are also found here with eagles, harriers, falcons, kestrel and vultures.

   4. Semi-Arid Region: the word arid has been taken from a Greek word ‘arere’ which means to be dry. The term arid normally means a region on the surface of the earth where rainfall is nil or inadequate which results into sparse vegetation. This region constitutes 16.6 per cent of the total geographical area of the country and it is a transition zone between the desert and the dense forest of Western Ghats. The Indian semi-arid region mainly lies in the states of Gujarat, Punjab, Haryana and western parts of Rajasthan. The rains are erratic and sometimes come with a heavy storm for short duration resulting in high runoff instead of replenishing the ground water. The semi arid vegetation chiefly consists of thorn-scrub forests of Capparis deciduas, Prosopis cineraria and Flacourftia. The availability of grass and palatable shrub layer in this zone supports the highest wildlife biomass. Sambar and Chital are restricted to the better wooded hills and moister valley areas respectively. Other endangered species supported by this region are Lion, Caracal, Jackal, Wolf.

    5. Western Ghats: this region constitutes 4.0 per cent of the total geographical area. The Western Ghats biogeographic zone comes next to Himalaya in floristic richness and diversity. About 4000 species of flowering plants are expected here of which 1500 are endemic species. The moist deciduous forests at lower elevation contain highly valued timber species such as Indian Rosewood (Dalbergia latifolia), Kauha/asaina/black murdah (Terminalia crenulata), Indian kino tree (Pterocarpus marsupium) and Teak (Tectona grandis). With respect to animals some significant endemic species to this region include Nilgiri Langur (Presbutis jobni), Lion Tailed Macaque (Macaca silenus), Grizzled Giant Squirrel (Ratufa macroura) and Malabar Grey Hornbill (Heosemys silvatica).

 

6. Deccan Plateau: this region is the India’s richest biogeographic region constituting 42.0 per cent of the total geographical area. It is a semi arid region that falls in the rain shadow area of the Western Ghats. This bio-geographic zone of peninsular India is by far the most extensive zone, covering India’s finest forests, particularly in the States of Madhya Pradesh, Maharashtra and Odisha. Majority of the forests are deciduous in nature. The Deccan highland constitutes the principal catchment for a number of south India’s main river systems (Narmada, Tapti, Mahanadi and Godavari). A major portion of the Deccan peninsula is covered by Tropical thorn forests and tropical dry and moist deciduous forests and degraded shrub lands. Teak (Tectona grandis), Axlewood (Anogeissus latifolia), Indian Frankincense (Boswellia serrata), Bustard Teak (Butea monosperma) are the thorny species of the semi arid zone. The tropical moist deciduous forest chiefly includes Kadam (Adina cardifolia), Satinwood/Buruta (Chloroxylon swietenia), Coromandel ebony/Tendu (Diospyros exsclupta). Animal species found in this region are Chital (Axis axis), Sambar (Cerves unicolor), Nilgai (Boselapbus gtragocamelus), Chousingha (Tetracerus quadricarnis), Barking dear, Gaur (Antilope cervicapra), Elephants (Elephas maximus) in Bihar-Odisha and Karnataka-Tamil Nadu belts. Moreover, Wild Buffalow and Swamp deers are found at the junction of Odisha, Madhya Pradesh and Maharashtra.

 

7. The Gangetic Plain: this region constitutes around 10.8 per cent of the total geographical area. This is the largest unit of the great plains of India stretching from Delhi to Kolkata covering the states of Uttar Pradesh, Bihar and West Bengal. The characteristic fauna in this region includes Rhino (Rhinoceros unicornis), Elephant (Elephas maximus), Buffalo (Babulus bubalis), Swamp Deer (Cervus duvauceli), Hog Deer (Axis porcinus) and Hispid Hare (Carprolagus bispidus). In this region the natural vegetation has been much replaced by cultivated plants. In the Terai areas i.e., the foothills of the Himalayas the natural vegetation comprises of tall grasses of Kangaroo Grass (Themeda), Saccharum and Phragmites (perennial grass). Other trees which are commonly found here are Shikakai, Neem, Mango, Mahua, Serpentine Wood and White Sandalwood. The most important thing about this region is that it is the food bowl of India and it provides foodgrains to millions of population because of its plain topography which is suitable for agriculture and the perennial rivers which provides irrigation throughout the year.

 

8. North-East Region: this region constitutes of 5.2 per cent of the total geographical area. The region represents the transition zone between Indian, Indo-Malayan and indo-Chinese biogeographical regions as well as being a meeting point of the Himalayan Mountains and Peninsular India. This zone is the richest in biological diversity at the community level, at the species level and in endemics. About 50 per cent of the total number of species of India occurs in this zone which also includes a portion of Arunachal Pradesh. This area has perhaps the most ancient species of living angiosperms and apart from this the rich concentration of primitive flowering plants, several others like orchids, bamboos, ferns, musaceae and cucurbitaceae exhibit maximum diversity here.

 

9. Coastal Region: this region constitutes of 2.5 per cent of the total geographical area with sandy beaches, mangroves, mud flats, coral reefs and marine angiosperms pastures make them the wealth and health zone of India. The coastline of India stretches from Gujarat to Cape Comorin in the east and includes two major vegetation type mangrove forests and beach forests. The most characteristic tree species of beach forests are Australian pine tree (Casuarina equisetifolia), Cashew tree (Anacardium occidentale) Indian doomba oiltree (Calophyllum inophyllum). A total of 25 islets constitute the Lakshadweep which are of coral origin and have a typical reef lagoon system, rich in biodiversity. The densely populated Lakshadweep islands virtually have no natural vegetation. The mangrove forests are found along the deltas, estuaries and backwaters and chiefly comprise the genera of true mangrove Rhizophora, Sonneratia, Heretiera, Xylocarpus.

 

10. Island: this region constitutes of 0.3 per cent of the total geographical area. The Andaman and Nicobar groups of island in the Bay of Bengal with 348 islands show an interesting biogeography. These islands are the centers of high endemism and contain some of India’s finest evergreen forests and support a wide diversity of corals. These islands support roughly 2200 species of higher plants. There are about 210 endemic species of which 75 are trees. The dense vegetation of the islands can be broadly classified as littoral and inland types. The littoral forests composed of trees like Andaman bulletwood/Sea Mahua (Manilkara), Indian doomba oiltree (Calophyllum inophyllum), Sea-almond/Indian-almond (Terminalia catappa) fish-poison tree/sea-poison tree (Barringtonia asiastica) and mangroves like red-mangrove/Asiatic-mangrove (Rhizophora mucronata), Garjan (R. apiculata), grey or white mangrove (Avicennia marina). The inland vegetation includes the evergreen and deciduous forests with a number of economically important timber species East Indian Mahogany (Pterocarpus dalbergioides), frywood (Albizzia lebbeck) and few others.

 

Table 1: Biogeographic classification and biotic provinces of India

 

 

 

 

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