🌾World Biogeography
The Indomalayan realm spans tropical Asia from Pakistan to Indonesia, boasting incredible biodiversity and unique evolutionary history. This vast region encompasses diverse landscapes, from towering Himalayas to lush rainforests and coastal mangroves, shaping distinct ecosystems and species adaptations.
Home to several biodiversity hotspots, the realm faces significant conservation challenges. Habitat loss, wildlife trafficking, and climate change threaten its rich flora and fauna. Understanding the complex biogeographical patterns and human impacts is crucial for developing effective strategies to protect this biologically important region.
Geographic extent
- Indomalayan realm encompasses a vast area of tropical Asia spanning from Pakistan to Indonesia
- Biogeographically significant region characterized by high biodiversity and unique evolutionary history
- Plays crucial role in understanding global patterns of species distribution and endemism
Boundaries of Indomalayan realm
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- Extends from the western edge of Pakistan to the Wallace Line in Indonesia
- Northern boundary includes southern China, encompassing parts of Yunnan and Guangxi provinces
- Southern limit reaches the islands of Java, Bali, and Borneo
- Eastern boundary defined by Wallace Line separates Indomalayan from Australasian realm
Major regions and countries
- Indian subcontinent includes India, Nepal, Bhutan, Bangladesh, and Sri Lanka
- Southeast Asian mainland comprises Myanmar, Thailand, Laos, Cambodia, and Vietnam
- Malay Peninsula and archipelagic regions include Malaysia, Singapore, Indonesia, and Philippines
- Southern portions of China fall within the realm's northern extent
- Western edge includes parts of Afghanistan and Pakistan
Physical characteristics
- Indomalayan realm exhibits diverse physical features shaped by tectonic activity and climate patterns
- Landscape ranges from towering mountain ranges to expansive coastal plains and tropical islands
- Physical characteristics strongly influence biodiversity patterns and species adaptations
Climate patterns
- Tropical monsoon climate dominates much of the realm
- Distinct wet and dry seasons driven by seasonal wind shifts
- Annual rainfall varies greatly, ranging from 2000-5000 mm in many areas
- High humidity levels persist throughout the year in most regions
- Localized microclimates exist due to variations in elevation and topography
Topography and landforms
- Himalayan mountain range forms the northern boundary, reaching elevations over 8000 meters
- Western Ghats and Eastern Ghats run along India's coasts, creating unique biodiversity hotspots
- Extensive river deltas (Ganges-Brahmaputra, Irrawaddy, Mekong) form fertile alluvial plains
- Volcanic island arcs in Indonesia and Philippines result from tectonic subduction zones
- Karst landscapes in Southeast Asia create distinctive habitats (Halong Bay, Gunung Mulu)
Major river systems
- Ganges-Brahmaputra system drains the northern Indian subcontinent
- Mekong River flows through six Southeast Asian countries, supporting diverse ecosystems
- Irrawaddy River in Myanmar forms a vast delta crucial for agriculture and biodiversity
- Chao Phraya River basin in Thailand supports extensive rice cultivation
- Kapuas River in Borneo represents one of the longest island rivers globally
Biodiversity hotspots
- Indomalayan realm contains several globally recognized biodiversity hotspots
- These areas harbor exceptional concentrations of endemic species facing significant threats
- Conservation efforts often focus on these hotspots due to their biological importance
Western Ghats
- Mountain range along India's western coast spanning approximately 1,600 km
- Recognized for high levels of plant and animal endemism
- Harbors over 5000 species of flowering plants, 139 mammal species, and 508 bird species
- Threatened by deforestation, mining activities, and hydroelectric projects
- Home to iconic species (lion-tailed macaque, Nilgiri tahr, purple frog)
Indo-Burma region
- Encompasses mainland Southeast Asia and northeastern India
- Characterized by diverse ecosystems including dry and moist deciduous forests
- Supports over 13,500 plant species, 1,330 bird species, and 350 mammal species
- Mekong River basin serves as a critical habitat for numerous aquatic species
- Faces threats from rapid development, agricultural expansion, and illegal wildlife trade
Sundaland
- Includes Malay Peninsula, Borneo, Sumatra, Java, and surrounding islands
- Formed by fluctuating sea levels during Pleistocene, creating land bridges between islands
- Exhibits high species richness and endemism in both flora and fauna
- Home to iconic species (orangutans, proboscis monkeys, Sumatran tigers)
- Rapidly losing forest cover due to palm oil plantations and logging activities
Philippines
- Archipelago of over 7,000 islands with complex geological history
- Exceptionally high rates of endemism across various taxonomic groups
- Supports over 6,000 plant species, 170 terrestrial mammal species, and 600 bird species
- Many species confined to single islands or island groups (Philippine eagle, tarsiers)
- Threatened by habitat loss, mining activities, and climate change impacts
Flora
- Indomalayan realm boasts incredibly diverse plant life adapted to various ecosystems
- Floral composition reflects complex biogeographical history and environmental gradients
- Plant communities play crucial roles in supporting fauna and ecosystem services
Tropical rainforest composition
- Dominated by tall, evergreen trees forming multi-layered canopy structure
- High species diversity with up to 300 tree species per hectare in some areas
- Dipterocarp family (Dipterocarpaceae) particularly prevalent in Southeast Asian forests
- Epiphytes abundant, including orchids, ferns, and bromeliads
- Lianas and strangler figs contribute to complex forest structure
- Understory composed of shade-tolerant plants adapted to low light conditions
Mangrove ecosystems
- Occur along coastal areas, river deltas, and estuaries throughout the realm
- Adapt to saline conditions with specialized root systems (pneumatophores, prop roots)
- Provide crucial ecosystem services (coastal protection, carbon sequestration, nursery habitats)
- Dominated by genera (Rhizophora, Avicennia, Sonneratia, Bruguiera)
- Face threats from aquaculture expansion, coastal development, and sea-level rise
- Sundarbans in Bangladesh and India represents world's largest contiguous mangrove forest
Monsoon forests
- Adapted to seasonal rainfall patterns with distinct wet and dry periods
- Trees often shed leaves during dry season to conserve water
- Characterized by lower species diversity compared to evergreen rainforests
- Important timber species (teak, sal) commonly found in these forests
- Provide habitat for diverse fauna adapted to seasonal resource availability
- Threatened by conversion to agriculture and altered fire regimes
Fauna
- Indomalayan realm supports a rich and diverse fauna adapted to various habitats
- Faunal assemblages reflect complex evolutionary history and biogeographical patterns
- Many species face significant conservation challenges due to human activities
Iconic mammals
- Asian elephant represents keystone species in forest ecosystems
- Tigers occur across various habitats, with several subspecies endemic to specific regions
- Orangutans found only in Borneo and Sumatra, representing unique Asian great apes
- Indian rhinoceros confined to small protected areas in India and Nepal
- Proboscis monkey endemic to Borneo, adapted to mangrove and riverine habitats
- Diverse primate fauna includes gibbons, langurs, and macaques
Reptile diversity
- Realm supports high diversity of reptiles adapted to various ecological niches
- Komodo dragon, world's largest lizard, endemic to Indonesian islands
- Reticulated python represents one of the world's longest snakes
- Gharial, a critically endangered crocodilian, confined to river systems in India and Nepal
- Flying lizards (genus Draco) showcase unique adaptations for gliding between trees
- Many endemic species found on islands (Philippine forest turtle, Sulawesi forest turtle)
Avian species
- Over 1,600 bird species recorded within the Indomalayan realm
- High endemism rates, particularly on islands and in montane regions
- Pheasants and hornbills represent characteristic groups with numerous endemic species
- Critically endangered species (Philippine eagle, Bali starling) face severe habitat loss
- Wetland areas support diverse waterfowl and migratory species
- Adaptive radiations observed in certain groups (flowerpeckers, sunbirds)
Endemic invertebrates
- Incredible diversity of invertebrates, many yet to be described scientifically
- Wallace's golden birdwing butterfly, one of the world's largest, found in Moluccas
- Numerous endemic land snail species on limestone karsts in Southeast Asia
- Giant stick insects (Phobaeticus) found in Borneo and other parts of Southeast Asia
- Bioluminescent click beetles in Southeast Asian rainforests
- Cave-dwelling invertebrates show high endemism in karst ecosystems
Evolutionary history
- Indomalayan realm's evolutionary history shaped by complex geological and climatic events
- Understanding this history crucial for interpreting current biodiversity patterns
- Ongoing research continues to refine our knowledge of the realm's biogeographical development
Geological formation
- Indian Plate's collision with Eurasian Plate ~50 million years ago initiated Himalayan orogeny
- Uplift of Tibetan Plateau significantly influenced regional climate patterns
- Formation of Indonesian archipelago through complex tectonic processes over millions of years
- Sundaland shelf repeatedly exposed and submerged due to sea-level fluctuations
- Philippine archipelago formed through combination of volcanic activity and plate movements
Pleistocene land bridges
- Sea level fluctuations during glacial periods exposed Sunda Shelf, connecting mainland Asia to Borneo, Java, and Sumatra
- Allowed dispersal of flora and fauna between islands and mainland, shaping current distributions
- Isolated populations during interglacial periods led to speciation events
- Repeated connection and isolation cycles contributed to complex patterns of endemism
- Some species (orangutans, Sumatran rhinoceros) show evidence of historical wider distributions
Wallacean transition zone
- Region between Sunda and Sahul shelves representing biogeographical transition
- Named after Alfred Russel Wallace, who first described faunal discontinuity
- Characterized by mix of Asian and Australian elements in flora and fauna
- Includes islands of Sulawesi, Moluccas, and Lesser Sunda Islands
- Unique species assemblages resulted from long isolation and limited dispersal opportunities
- Ongoing research refines understanding of biogeographical boundaries within this zone
Biogeographical patterns
- Indomalayan realm exhibits complex patterns of species distribution and diversity
- Understanding these patterns crucial for effective conservation planning
- Ongoing research continues to uncover new insights into biogeographical processes
Species richness gradients
- Generally decreasing species richness from equator towards higher latitudes
- Elevational gradients in species richness vary among taxonomic groups
- Mid-elevation bulge in diversity observed in some montane regions
- Hotspots of species richness often correspond with areas of high habitat heterogeneity
- Island biogeography principles influence species richness on different-sized islands
- Edge effects at ecosystem boundaries can create localized areas of high species richness
Endemism rates
- Highest endemism rates typically found on isolated islands and in montane regions
- Philippines recognized for exceptionally high rates of endemism across taxa
- Western Ghats-Sri Lanka hotspot exhibits high plant and amphibian endemism
- Sulawesi's unique geological history resulted in high endemism rates for various groups
- Karst ecosystems often harbor locally endemic invertebrate species
- Endemism patterns reflect historical isolation, dispersal barriers, and adaptive radiations
Dispersal barriers
- Wallace Line represents major faunal boundary between Asian and Australian realms
- Mountainous regions (Himalayas, Annamite Range) act as barriers for lowland species
- Deep sea trenches limit dispersal between island groups in archipelagic regions
- Rivers can serve as barriers for certain terrestrial species (primates, small mammals)
- Habitat specialization limits dispersal for some species across different ecosystem types
- Human-made barriers (roads, dams) increasingly fragment populations and limit gene flow
Conservation issues
- Indomalayan realm faces numerous conservation challenges threatening its unique biodiversity
- Understanding these issues crucial for developing effective conservation strategies
- Addressing conservation concerns requires collaborative efforts at local, national, and international levels
Habitat fragmentation
- Widespread issue across the realm due to human activities
- Reduces habitat connectivity, impacting species movement and gene flow
- Increases edge effects, altering microclimates and species compositions
- Particularly problematic for large-ranging species (tigers, elephants)
- Creates isolated populations more vulnerable to local extinctions
- Restoration of habitat corridors represents key conservation strategy
Deforestation impacts
- Major driver of biodiversity loss across the Indomalayan realm
- Caused by various factors (agricultural expansion, logging, infrastructure development)
- Leads to loss of critical habitats for numerous species
- Disrupts ecosystem services (water regulation, carbon sequestration, soil stability)
- Particularly severe in Indonesia and Malaysia due to palm oil industry expansion
- Efforts to implement sustainable forest management and reduce deforestation rates ongoing
Wildlife trafficking
- Significant threat to many species within the realm
- Driven by demand for traditional medicine, exotic pets, and luxury items
- Particularly impacts charismatic species (tigers, pangolins, elephants)
- International criminal networks often involved in large-scale trafficking operations
- Enforcement challenges due to porous borders and limited resources
- Efforts to reduce demand and strengthen law enforcement crucial for addressing this issue
Climate change effects
- Increasing temperatures and changing precipitation patterns impact ecosystems
- Sea-level rise threatens coastal and island habitats
- Altered phenology affects species interactions and ecosystem functioning
- Range shifts observed for some species, potentially leading to community disruptions
- Increased frequency and intensity of extreme weather events (droughts, floods)
- Coral reef ecosystems particularly vulnerable to ocean acidification and warming
Human impact
- Human activities significantly shape biodiversity patterns and conservation challenges in the Indomalayan realm
- Understanding human-environment interactions crucial for developing sustainable management strategies
- Balancing human needs with biodiversity conservation represents ongoing challenge
Population pressures
- Indomalayan realm home to over 2 billion people, with population continuing to grow
- High population densities in many areas increase demand for natural resources
- Encroachment into natural habitats leads to human-wildlife conflicts
- Overharvesting of plant and animal species for local use and commercial trade
- Pollution from dense urban areas impacts terrestrial and aquatic ecosystems
- Efforts to promote sustainable livelihoods and family planning ongoing in many regions
Agricultural expansion
- Major driver of habitat loss and fragmentation across the realm
- Conversion of forests to palm oil plantations particularly significant in Southeast Asia
- Rice cultivation dominates many lowland areas, altering natural hydrology
- Intensification of agriculture leads to increased pesticide and fertilizer use
- Slash-and-burn agriculture in upland areas contributes to soil erosion and habitat loss
- Promoting sustainable agricultural practices and land-use planning crucial for conservation
Urbanization trends
- Rapid urban growth occurring across much of the Indomalayan realm
- Mega-cities (Mumbai, Jakarta, Manila) place immense pressure on surrounding ecosystems
- Urban expansion often occurs in biodiversity-rich coastal and lowland areas
- Increased demand for construction materials impacts forests and river systems
- Urban heat island effect and pollution impact local climate and air quality
- Some cities implementing green infrastructure and urban biodiversity initiatives
Protected areas
- Protected areas play crucial role in conserving biodiversity within Indomalayan realm
- Vary in size, management approaches, and effectiveness across different countries
- Ongoing efforts to expand and improve protected area networks throughout the region
National parks
- Kaziranga National Park in India protects important populations of Indian rhinoceros and tigers
- Gunung Leuser National Park in Indonesia harbors diverse ecosystems and serves as orangutan stronghold
- Khao Yai National Park in Thailand represents one of Southeast Asia's largest monsoon forests
- Kinabalu Park in Malaysia protects unique montane ecosystems with high plant endemism
- Chitwan National Park in Nepal supports important populations of tigers and greater one-horned rhinoceros
Wildlife sanctuaries
- Sundarbans Wildlife Sanctuary spans India and Bangladesh, protecting world's largest mangrove forest
- Thung Yai-Huai Kha Khaeng Wildlife Sanctuaries in Thailand harbor diverse large mammal assemblages
- Srepok Wildlife Sanctuary in Cambodia provides crucial habitat for endangered large mammals
- Sepilok Orangutan Rehabilitation Centre in Malaysia focuses on orangutan conservation and research
- Danum Valley Conservation Area in Borneo protects large tract of primary lowland rainforest
Biosphere reserves
- Nilgiri Biosphere Reserve in India encompasses diverse ecosystems across Western Ghats
- Cat Tien Biosphere Reserve in Vietnam protects lowland forests and wetlands
- Palawan Biosphere Reserve in Philippines recognized for high biodiversity and endemism
- Manas Biosphere Reserve in India supports important populations of tigers and Indian elephants
- Tasek Bera Biosphere Reserve in Malaysia protects unique peat swamp ecosystem
Biogeographical research
- Ongoing research in Indomalayan realm continues to advance our understanding of biodiversity patterns and processes
- Interdisciplinary approaches increasingly used to address complex conservation challenges
- Research findings inform conservation strategies and policy decisions
Key studies in Indomalayan realm
- Wallace's work on biogeographical boundaries between Asian and Australian faunas
- MacArthur and Wilson's studies on island biogeography in Indonesian archipelago
- Ashton's research on dipterocarp forest ecology and biogeography in Southeast Asia
- Corlett's work on tropical rainforest ecology and anthropogenic impacts
- Sodhi et al.'s comprehensive assessment of Southeast Asian biodiversity crisis
Current research priorities
- Refining understanding of species distributions and population trends
- Investigating impacts of climate change on biodiversity and ecosystem functioning
- Assessing effectiveness of protected areas and identifying priority areas for conservation
- Studying ecosystem services provided by Indomalayan biodiversity
- Developing innovative approaches for biodiversity monitoring and conservation
Future conservation strategies
- Implementing ecosystem-based approaches to conservation planning
- Strengthening transboundary cooperation for managing shared ecosystems
- Developing sustainable financing mechanisms for long-term conservation efforts
- Integrating traditional ecological knowledge into conservation practices
- Promoting nature-based solutions for climate change mitigation and adaptation
- Enhancing capacity building and environmental education programs throughout the realm