Define Biogeographic Regions
Biogeography is the scientific investigation of the distribution of species and ecosystems in geographic setting and across geological time. Biological communities and living Organisms often differ in a regular fashion through geographic gradients of elevation, isolation, latitude, and habitat area.
The biogeographic regions are basically “those predominant divisions of the earth’s surface of estimated continental extent, which are attributed by distinct assemblages of animal types”. That said, a Biogeographic region is basically an area of plant and animal distribution consisting of similar or shared properties throughout.
Introduction and Identification of Biogeographic Zones
Zone 1 – Trans-Himalayan
In the immediate north of the Great Himalayan range are the Trans-Himalayas which encapsulates three biogeographic provinces i.e. — Himalayan Sikkim, Ladakh mountains, and Tibetan plateau. It constitutes about 5.6% of the country's landmass. This area mostly lies between 14,800 to 19,700 feet and is very cold and dry. The extensive region of Trans-Himalayan comprises bare rock and glaciers. The only vegetation is the scanty alpine steppe. With its scanty vegetation, it has a superfluous wild sheep and goat community in the world. The snow leopard, black bears, marbled cat, marmots, wolf and kiang can be spotted here, as are the migratory Black-necked Cranes.
Zone 2 – Himalayas
This representation of the Himalayas has the youngest and loftiest mountain sequences in the world. The 2,400 kilometres long Himalayan mountain arc contains distinctive biodiversity in wake of its high altitude, rich flora, soothing temperature and steep gradient. Biogeographically, they create a part of the Palearctic realm. The Himalayas contain three biogeographical provinces i.e. — Central Himalayas, East Himalayas, West Himalayas, and Northwest Himalayas, which together comprise about 6.4% of the country's area.
Zone 3 – The Indian Desert
This area comprises two biogeographical provinces i.e. The Thar desert and The Rann of Kutch. The larger is the Thar or Great Indian Desert, consisting of Rajasthan and parts of Haryana and Punjab, moreover adjoining Pakistan. The Indian part of the Thar Desert occupies 170,000 km. The climate reflects very hot and dry summers while cold and arid winters. The area experiences rainfall less than 70 cm. A highly endangered bird—The Indian Bustard is found here, in addition to foxes, snakes, camels, gazelles, foxes, and spiny-tailed lizards.
The second biogeographical province— The Rann of Kutch that lies in Gujarat is a vast area of salt marsh spread across the border between India and Pakistan. This larger area has desert on one side and the sea on the other allowing several ecosystems and desert vegetation. Its deserts and grasslands are home to various wildlife that have adapted to its harsh conditions. These account for endangered and endemic animal and plant species, like the Indian wild ass. The Rann is home to many domestic and migratory birds such as the greater flamingo, lesser flamingo and the Houbara bustard. The Little Rann is an accommodation to the world's largest population of Indian wild ass with other mammals including the Indian wolf, desert fox, blackbuck, chinkara and others.
Zone 4 - Semi-Arid Areas
A transitional zone between the desert and the denser forests of the Western Ghats are the semi-arid areas. The area is characterized by discontinuous vegetation blanketed with bare soil and soil water that remains in deficit throughout the year.
Zone 5 - Western Ghats
The mountains running through the west coast of peninsular India comprising one of the unique biological regions of the world are the Western Ghats.
The diverse topography and different climate develop a wide range of habitats that support distinctive sets of plant and animal species. The Western Ghats hills are amongst the 25 biodiversity hot-spots identified globally, known for their high levels of endemism and association with evergreen forests.
Zone 6 - Deccan Plateau
On the farther side of Ghats is the Deccan Plateau, the largest unit of the Peninsular Plateau of India. The highlands of Deccan are blanketed with unique types of forests that offer a wide variety of forest products.
Zone 7 - Gangetic Plain
The biggest unit of the Great Plain of India is the Gangetic Plain. River Ganga is the main water stream after whose name this plain is named. The thickness of the plain is characterized by the alluvial sediments that vary significantly with their maximum in the Ganga plains.
Some of the highest population densities and Topographic uniformity from the trees belonging to these forests are teak, shisham, sal, khair etc.
Zone 8 - North-East India
One of the poorest regions in the country consists of several species of bamboos, orchids, ferns and other plants. Here the wild relatives of plants such as mango, banana, citrus and pepper can be grown and found.
Zone 9 - Islands
Comprising two groups of islands, i.e., the Arabian Sea and Bay Islands vary considerably in origin and physical features.
Zone 10 - Coasts
The Indian coasts differ in their structures and features with the Indian coastline extending over 7,516. 4 km. Extensive deltas of Krishna, Kaveri and Godavari, are the prominent features of this coast. Mangrove vegetation along the tracts of the coast at Ratnagiri in Maharashtra is a reflection of coastal plains. Different crops are grown with Rice being the main crop of cultivation. Coconut trees grow on the coastal plains.
FAQs on Biogeographic Regions
1. What is a biogeographic region?
A biogeographic region is a large-scale area of the Earth's surface where plants and animals have developed in relative isolation over long periods. These regions are defined by the shared evolutionary history and distribution of their species. The organisms within one region have more in common with each other than with organisms in another region, often due to separation by major physical barriers like oceans, deserts, or mountain ranges.
2. What are the main criteria used to define a biogeographic region?
The primary criteria for defining and identifying a biogeographic region include:
Endemism: The presence of species, genera, or families that are unique to that region and found nowhere else on Earth.
Taxonomic Richness: The region must be rich in the majority of living taxa (groups of organisms).
Geographic Boundaries: They are typically based on major geographical divisions, such as continents separated by vast oceans or large mountain ranges that restrict the movement of species.
3. What is the difference between a biogeographic region, a biome, and an ecosystem?
These terms describe different ecological concepts:
Biogeographic Region: Focuses on the evolutionary history and distribution of species on a very large, often continental, scale.
Biome: Is defined by climate and dominant vegetation. The same biome (e.g., a desert) can exist in different biogeographic regions (e.g., the Sahara in the Palearctic realm and the Atacama in the Neotropical realm).
Ecosystem: Refers to the direct interaction between living organisms and their physical environment in a specific area. It can be as small as a pond or as large as a forest.
4. How many major biogeographic realms are recognised globally?
The world is divided into eight major biogeographic realms, each representing a large area with a distinct evolutionary history. These realms are the Palearctic, Nearctic, Afrotropical, Neotropical, Australasian, Indomalayan, Oceanian, and Antarctic.
5. How do physical barriers like oceans or mountains create unique biogeographic regions?
Physical barriers are crucial in forming distinct biogeographic regions through a process called vicariance. When a barrier like a mountain range or an ocean splits a species' ancestral population, it prevents gene flow between the separated groups. Over millions of years, these isolated populations evolve independently, adapting to their unique local environments. This leads to the emergence of new, endemic species and results in the distinct flora and fauna that characterise a biogeographic region, such as the unique marsupials of Australia.
6. Why is classifying the world into biogeographic regions important for environmental conservation?
This classification is vital for conservation efforts because it helps scientists and policymakers to:
Identify biodiversity hotspots with high concentrations of endemic and threatened species.
Set global priorities for protecting unique evolutionary lineages.
Understand the natural distribution of species to better manage and prevent the spread of invasive species.
Design effective, large-scale conservation networks that span across political borders.
7. What are the 10 biogeographic zones of India?
Based on the classification by the Wildlife Institute of India (WII), India is divided into 10 distinct biogeographic zones. These are:
Trans-Himalayan Zone
Himalayan Zone
Indian Desert Zone
Semi-Arid Zone
Western Ghats Zone
Deccan Plateau Zone
Gangetic Plain Zone
North-East Zone
Coastal Zone
Islands
8. Which biogeographic zone in India is a major biodiversity hotspot?
The Western Ghats zone is globally recognised as one of the world's most significant biodiversity hotspots. Its high levels of rainfall and unique topography have led to an incredible richness of life, including a very high number of endemic species of plants, amphibians, reptiles, and insects that are found nowhere else on the planet. The North-East zone is another major biodiversity hotspot in India.
