Module 70. Biomes and Biogeographic Regions of the World & India

The Earth’s surface displays remarkable diversity in climate, vegetation, and animal life. These variations give rise to distinct biomes and biogeographic regions, which collectively represent the ecological and geographical framework of the planet’s biosphere. Understanding these divisions is crucial for studying biodiversity, ecological balance, and environmental conservation, both globally and within India.

Concept of Biomes

A biome is a large ecological unit characterised by its distinctive climate, soil, vegetation, and animal communities. It represents the world’s major ecosystems, shaped primarily by temperature, precipitation, and latitude. Biomes may be terrestrial or aquatic, each supporting unique life forms adapted to their environments.
Major Determinants of Biomes:

• Climatic Factors: Temperature, rainfall, and humidity govern vegetation types.
• Edaphic Factors: Soil composition, fertility, and moisture influence plant growth.
• Topographic Factors: Altitude, slope, and aspect affect climate and biodiversity.
• Latitude and Longitude: Affect sunlight intensity and seasonal variations.

Major Biomes of the World

The world’s terrestrial ecosystems are generally grouped into several major biomes:

1. Tropical Rainforest Biome:
   • Found near the equator (e.g., Amazon Basin, Congo Basin, Southeast Asia).
   • High rainfall (>200 cm annually) and temperature (~27°C) support dense evergreen forests.
   • Dominant vegetation: mahogany, ebony, rubber trees.
   • Rich biodiversity with species such as jaguars, monkeys, toucans, and numerous reptiles.
2. Tropical Deciduous (Monsoon) Forest Biome:
   • Occurs in South Asia, parts of Africa, and Central America.
   • Experiences seasonal rainfall; trees shed leaves during the dry season.
   • Vegetation includes teak, sal, and bamboo.
   • Fauna: elephants, tigers, and deer.
3. Savanna Biome:
   • Tropical grasslands between forests and deserts (e.g., African Savannah).
   • Characterised by scattered trees and seasonal droughts.
   • Animals include lions, giraffes, zebras, and antelopes.
4. Desert Biome:
   • Found around 30° latitude (e.g., Sahara, Arabian, Thar, Mojave).
   • Very low rainfall (<25 cm annually); extreme temperature variations.
   • Vegetation: xerophytes like cacti and acacia.
   • Fauna: camels, reptiles, rodents.
5. Temperate Grassland Biome:
   • Found in interiors of continents (e.g., Prairies, Steppes, Pampas).
   • Moderate rainfall and fertile soil; ideal for agriculture.
   • Fauna includes bison, antelope, and prairie dogs.
6. Temperate Forest Biome:
   • Occurs in mid-latitude regions with moderate climate (e.g., Europe, eastern USA, Japan).
   • Mixed forests with deciduous and coniferous trees like oak, maple, and pine.
   • Fauna: deer, bears, and birds.
7. Taiga (Boreal Forest) Biome:
   • Found in subarctic zones (e.g., Canada, Russia, Scandinavia).
   • Dominated by conifers such as spruce, fir, and pine.
   • Cold climate with long winters.
8. Tundra Biome:
   • Found in Arctic regions and high mountain tops.
   • Permafrost and low temperatures restrict vegetation to mosses, lichens, and shrubs.
   • Animals: reindeer, arctic foxes, polar bears.
9. Mountain (Alpine) Biome:
   • Found at high altitudes (e.g., Himalayas, Andes, Rockies).
   • Vegetation varies with altitude—ranging from temperate forests to alpine meadows.
   • Fauna: snow leopards, yaks, and mountain goats.
10. Aquatic Biomes:
    • Divided into marine (oceans, seas, coral reefs) and freshwater (rivers, lakes, wetlands).
    • Marine ecosystems regulate global climate and support diverse organisms like fish, coral, and plankton.

Biogeographic Regions of the World

The world is divided into broad biogeographic regions or realms, each representing a distinct evolutionary history of flora and fauna.
1. Nearctic Region: Covers North America; features prairies, coniferous forests, and deserts. Common fauna include bison, bears, and raccoons.
2. Neotropical Region: Includes South and Central America. Rich in tropical rainforests and biodiversity; home to jaguars, sloths, and macaws.
3. Palaearctic Region: Covers Europe, North Africa, and northern Asia. Characterised by temperate forests and tundra; fauna includes wolves, deer, and rodents.
4. Ethiopian (Afrotropical) Region: Encompasses Africa south of the Sahara. Known for savannas, deserts, and rainforests. Fauna: elephants, lions, zebras, and giraffes.
5. Oriental Region: Covers South and Southeast Asia, including India, Sri Lanka, and the Malay Archipelago. Vegetation ranges from tropical forests to deserts. Fauna: tigers, elephants, and monkeys.
6. Australasian Region: Comprises Australia, New Guinea, and nearby islands. Unique fauna include kangaroos, koalas, and platypuses, reflecting long isolation.
7. Antarctic Region: Covers Antarctica and nearby islands. Extremely cold and barren; dominated by penguins, seals, and seabirds.

Biogeographic Regions of India

India exhibits extraordinary ecological diversity due to variations in climate, relief, and vegetation. The Zoological Survey of India (Rodgers and Panwar, 1988) classified the country into ten biogeographic zones.
1. Trans-Himalayan Region: Covers Ladakh, northern Kashmir, and parts of Himachal Pradesh. Characterised by cold desert climate and sparse vegetation. Fauna includes snow leopard, yak, and Tibetan antelope.
2. Himalayan Region: Extends across Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, and Arunachal Pradesh. It features alpine forests, grasslands, and coniferous trees. Species include red panda, Himalayan tahr, and musk deer.
3. Indian Desert Region: Covers western Rajasthan and parts of Gujarat. Arid climate with xerophytic vegetation like acacia and cacti. Fauna includes chinkara, desert fox, and great Indian bustard.
4. Semi-Arid Region: Lies between the desert and central highlands. Vegetation comprises dry deciduous forests and thorny scrub. Fauna: blackbuck, nilgai, and peafowl.
5. Western Ghats: Stretching along the western coast, this zone is a biodiversity hotspot. Dense evergreen and semi-evergreen forests dominate. Endemic species include lion-tailed macaque and Malabar civet.
6. Deccan Plateau: Covers central and southern India. Predominantly tropical dry deciduous forests with species like teak and sal. Fauna includes tiger, leopard, and gaur.
7. Gangetic Plain: Extends from Punjab to West Bengal. Fertile alluvial plains with rich agriculture. Fauna: rhinoceros (in parts of Assam and West Bengal), elephants, and migratory birds.
8. North-East Region: Comprising the states of Assam, Meghalaya, Nagaland, Manipur, Mizoram, Tripura, and Arunachal Pradesh. Characterised by high rainfall, dense forests, and rich biodiversity. Home to hoolock gibbon and clouded leopard.
9. Coastal Region: Covers eastern and western coastal plains. Features mangroves, estuaries, and lagoons. Notable fauna include olive ridley turtles, crocodiles, and flamingos.
10. Islands: Includes the Andaman and Nicobar Islands and Lakshadweep. The Andaman group has tropical rainforests and coral reefs, while Lakshadweep is known for its lagoons. Species include dugongs and marine turtles.

Ecological Significance and Conservation

Understanding biomes and biogeographic regions is essential for biodiversity conservation and sustainable development. Each region contributes uniquely to ecosystem services such as climate regulation, carbon sequestration, and genetic diversity.
India’s commitment to conservation is reflected in initiatives like the Biosphere Reserve Programme, Wildlife Protection Act (1972), and National Biodiversity Mission. Protected areas such as Kaziranga, Sundarbans, and Silent Valley preserve representative ecosystems of these biogeographic zones.