The Indomalaya Realm stands as one of Earth’s eight major biogeographical realms, representing a vast expanse of land defined by its distinct collection of plant and animal species. A biogeographical realm is a large, geographically distinct area where organisms have evolved in relative isolation over extended periods, leading to shared evolutionary histories and unique patterns of life. These realms are delineated by significant natural barriers, such as oceans, deserts, or high mountain ranges, which limit species migration and foster the development of unique ecosystems.
Geographical Scope and Defining Features
The Indomalaya Realm, also known as the Oriental realm, spans a considerable portion of tropical Asia, extending from the Indian subcontinent across Southeast Asia and into southern parts of East Asia. This broad area includes most of India, Bangladesh, Nepal, Bhutan, Sri Lanka, and eastern Pakistan. It encompasses the entire Indochinese Peninsula, reaching northward to the edge of the Yunnan-Guizhou plateau in China, and stretches through Indonesia to islands like Sumatra, Java, Bali, and Borneo. The realm also incorporates the Philippines, lowland Taiwan, and Japan’s Ryukyu Islands.
The physical characteristics of the Indomalaya Realm are as diverse as its geographical extent, shaped by tectonic activity and varied climate patterns. Landscapes range from towering mountain ranges, such as the Himalayas in the west, to expansive coastal plains and numerous tropical islands. The region is predominantly characterized by tropical and subtropical moist broadleaf forests, with tropical and subtropical dry broadleaf forests found in much of India and parts of Southeast Asia. High rainfall and a tropical monsoon climate are common, creating environments conducive to a rich array of life forms.
Remarkable Biodiversity
The Indomalaya Realm is globally recognized for its extraordinary variety of life, sheltering approximately one-fifth of the Earth’s plant, animal, and marine species. This region is home to numerous iconic and endemic species, meaning they are found nowhere else on Earth. Among the large mammals, the realm supports populations of leopards, tigers, water buffalos, Asian elephants, Indian rhinoceroses, Javan rhinoceroses, Malayan tapirs, orangutans, and gibbons. The rusty-spotted cat is also found here, particularly in India and Sri Lanka.
Bird diversity is impressive, with over 1,600 recorded species and high rates of endemism, especially on islands and in montane regions. Characteristic bird groups include pheasants and hornbills. The realm also boasts three endemic bird families: the Irenidae (fairy bluebirds), Megalaimidae, and Rhabdornithidae (Philippine creepers). Reptiles like king cobras and various monitor lizards are present, alongside a rich amphibian population. Indomalaya hosts about 1,000 species of amphibians across 81 genera, with around 80% of these being endemic.
Plant diversity is remarkable, featuring trees from the Dipterocarpaceae and Fabaceae families. Teak (Tectona) is a characteristic tree of the seasonally dry forests extending from India through Indochina, Malaysia, and the Philippines. Tropical pitcher plants (Nepenthes) are also characteristic, with highest diversity in Sumatra, Borneo, and the Philippines. The parasitic Rafflesiaceae family, which includes Rafflesia arnoldii, is also found here.
Conservation Challenges
Despite its immense biodiversity, the Indomalaya Realm confronts major threats. Extensive deforestation is a primary challenge. Large areas of forest are cleared for agricultural expansion and commercial logging. This habitat destruction leads to fragmentation, isolating animal populations and making them more vulnerable to decline.
The illegal wildlife trade and poaching are another major threat across the realm. Many of the region’s species, including tigers, pangolins, and rhinos, are sought after in illicit markets, leading to rapid population declines. Pollution, from industrial activities and inadequate waste management, further degrades ecosystems and harms both terrestrial and aquatic life.
The impacts of climate change also affect the Indomalaya Realm. Changing weather patterns, increased extreme weather events, and rising temperatures disrupt ecological balances, affecting species distributions and ecosystem health. These combined pressures are pushing many species toward extinction, highlighting the urgent need for concerted conservation efforts.