Module 72. Biodiversity, Fauna and Flora of the World

Biodiversity refers to the variety and variability of life forms on Earth, encompassing all living organisms—plants, animals, fungi, and microorganisms—and the ecosystems they inhabit. It represents the intricate web of life that sustains ecological balance, supports human livelihoods, and maintains natural processes essential for the planet’s health. The diversity of fauna (animals) and flora (plants) across the world is a result of millions of years of evolutionary adaptation shaped by climate, geography, and ecological interactions.

Concept and Levels of Biodiversity

The term biodiversity was popularised in the late 20th century to describe the full spectrum of life on Earth. It operates at three interrelated levels:

• Genetic Diversity: Variation of genes within species, which enables populations to adapt to changing environments and resist diseases.
• Species Diversity: Variety of different species within a region or ecosystem.
• Ecosystem Diversity: Range of different habitats, communities, and ecological processes within the biosphere.

These levels collectively ensure ecosystem stability and productivity. For instance, tropical rainforests and coral reefs, which have high species diversity, are more resilient to environmental stress than less diverse ecosystems.

Global Patterns of Biodiversity

Biodiversity is not uniformly distributed across the Earth. Its distribution follows clear geographic and climatic gradients.

• Latitudinal Gradient: Biodiversity tends to be highest near the equator and declines toward the poles. Tropical regions such as the Amazon Basin, the Congo Basin, and Southeast Asia harbour the greatest species richness due to warm temperatures, abundant rainfall, and long-term ecological stability.
• Altitudinal Gradient: Biodiversity decreases with increasing altitude, as temperature and oxygen levels drop. However, mountain ranges such as the Andes and Himalayas support unique endemic species adapted to specific niches.
• Marine vs Terrestrial Biodiversity: While terrestrial ecosystems contain most known species, oceans harbour vast yet less-studied biodiversity, including coral reefs, mangroves, and deep-sea ecosystems. Coral reefs alone support about 25 per cent of marine species despite covering less than 1 per cent of the ocean floor.

The world’s biodiversity hotspots—regions with exceptional levels of endemism and severe habitat loss—include the Western Ghats, Madagascar, Sundaland, Mesoamerica, and Tropical Andes, among others.

Flora of the World

The world’s flora comprises an estimated 390,000 known plant species, ranging from microscopic algae to towering trees. Plant diversity is fundamental to all ecosystems, forming the basis of food webs and providing oxygen, raw materials, and medicinal resources.
Major types of vegetation and their characteristics include:

• Tropical Rainforests: Found in equatorial regions of South America, Africa, and Southeast Asia, these forests contain the richest plant diversity, with thousands of tree and epiphyte species such as mahogany, teak, orchids, and bromeliads.
• Temperate Forests: Common in North America, Europe, and East Asia, these regions are dominated by deciduous trees like oak, maple, and beech that shed leaves seasonally.
• Coniferous Forests (Taiga): Stretching across northern latitudes, these forests are composed mainly of pine, spruce, and fir, adapted to cold climates.
• Grasslands (Savannas and Prairies): Characterised by grasses and scattered trees, these regions support herbivores such as bison, antelope, and zebras.
• Deserts: Sparse vegetation such as cacti, succulents, and drought-resistant shrubs thrive here under extreme aridity.
• Tundra: Found in polar regions, this biome supports mosses, lichens, and small shrubs adapted to freezing conditions and short growing seasons.

Human dependence on flora is immense—plants provide food, fibre, timber, fuel, and medicine. Nearly 80 per cent of the global population relies on plant-derived medicines for primary healthcare needs.

Fauna of the World

The world’s fauna is equally diverse, encompassing millions of species that occupy every conceivable habitat. Animals play crucial ecological roles such as pollination, seed dispersal, nutrient cycling, and maintaining trophic balance.
Major faunal groups include:

• Mammals: Over 6,400 species exist globally, ranging from the blue whale—the largest animal on Earth—to tiny shrews. Africa’s savannas host the greatest diversity of large mammals, while regions like Australia and Madagascar are rich in endemic marsupials and primates.
• Birds: More than 11,000 bird species inhabit the world, with tropical regions such as the Amazon and Southeast Asia showing peak diversity. Birds serve as pollinators, scavengers, and environmental indicators.
• Reptiles and Amphibians: Representing ancient evolutionary lineages, these cold-blooded animals are found mostly in tropical and subtropical regions. Amphibians are among the most threatened groups due to habitat loss and climate change.
• Fishes: With over 34,000 species, fishes form the most diverse group of vertebrates, inhabiting rivers, lakes, and oceans. Coral reefs and freshwater ecosystems host many endemic fish species.
• Invertebrates: Representing nearly 90 per cent of all known animal species, invertebrates—such as insects, molluscs, crustaceans, and arachnids—are vital for pollination, decomposition, and soil formation.

Faunal diversity is highest in countries like Brazil, Indonesia, and Australia, known as “megadiverse nations”.

Biodiversity Hotspots and Endemism

Biodiversity hotspots are regions with high species endemism under severe threat from human activity. The concept, introduced by Norman Myers in 1988, identifies areas that contain at least 1,500 endemic plant species and have lost over 70 per cent of original habitat. There are 36 recognised global hotspots, including:

• The Amazon Basin (South America)
• The Congo Basin (Africa)
• Madagascar and the Indian Ocean Islands
• Indo-Burma and Sundaland (Southeast Asia)
• The Western Ghats and Himalayas (India)
• The Caribbean and Mesoamerica

These hotspots are vital for global conservation efforts since they contain a majority of the world’s terrestrial biodiversity within relatively small geographical areas.

Threats to Global Biodiversity

Human activities have become the primary drivers of biodiversity loss. Major threats include:

• Habitat Destruction: Deforestation, urbanisation, and agricultural expansion cause habitat fragmentation and loss.
• Overexploitation: Unsustainable hunting, fishing, and timber extraction lead to species depletion.
• Pollution: Industrial effluents, pesticides, and plastics disrupt ecosystems and harm wildlife.
• Climate Change: Rising temperatures, changing rainfall patterns, and extreme weather events affect species distribution and survival.
• Invasive Species: Non-native species often outcompete local species, disrupting ecological balance.

According to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), around one million species face extinction within the coming decades if current trends continue.

Global Conservation Efforts

Conservation of biodiversity has become a key international priority. Global frameworks and conventions have been established to safeguard natural resources and promote sustainable development.
Major international initiatives include:

• Convention on Biological Diversity (CBD, 1992): Aims to conserve biodiversity, ensure sustainable use, and promote fair sharing of genetic resources.
• Convention on International Trade in Endangered Species (CITES, 1973): Regulates global trade in endangered flora and fauna.
• Ramsar Convention (1971): Focuses on the protection of wetlands of international importance.
• UNESCO’s Man and the Biosphere (MAB) Programme: Promotes the establishment of biosphere reserves for sustainable conservation.
• IUCN Red List: Assesses the conservation status of species worldwide, classifying them from “Least Concern” to “Critically Endangered”.

At the national level, countries adopt protected area networks—such as national parks, wildlife sanctuaries, and biosphere reserves—to preserve ecosystems and species. For example, India has more than 900 protected areas, including renowned sites like Kaziranga National Park, Sundarbans, and Nilgiri Biosphere Reserve.

Significance of Biodiversity to Humanity

Biodiversity underpins human survival and well-being. It provides:

• Ecological Services: Pollination, nutrient cycling, soil formation, and climate regulation.
• Economic Benefits: Resources for agriculture, medicine, forestry, and tourism.
• Cultural and Aesthetic Value: Many societies have spiritual and cultural ties to natural landscapes and species.

In modern times, the concept of sustainable development and the UN Sustainable Development Goals (SDGs) highlight the need to integrate biodiversity conservation with economic growth and poverty reduction.