Tropical Asia harbours a quarter of Earth’s species: knowledge gaps and priorities for protecting a global biodiversity hotspot
This study synthesizes biodiversity data for Tropical Asia, revealing that the region harbors nearly a quarter of global species diversity with significant knowledge gaps, high rates of ongoing species discovery, and substantial extinction risks that are exacerbated by outdated assessments and insufficient conservation monitoring.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
The Earth is a planet teeming with life, but that life is not spread out evenly. Some places are bursting with species found nowhere else, while others are more uniform. Scientists call these rich, unique places biodiversity hotspots. To understand them, researchers rely on two main ideas: species richness, which is simply a count of how many different kinds of living things live in an area, and endemism, which describes species that have evolved in isolation and exist only in that specific place. Knowing where these species live and how many there are is the first step to protecting them. Without a clear map of what exists, conservation efforts are like trying to save a library without knowing which books are missing or which are on the verge of being burned.
A massive new study has turned its gaze toward Tropical Asia, a vast region stretching from India and Sri Lanka in the west, across Southeast Asia, to the islands of Indonesia and the Philippines, and eastward to New Guinea. This area is a biological powerhouse, yet it remains one of the least understood corners of the planet. A team of over sixty researchers, working from institutions across the globe, set out to fill in the blanks. They gathered every available piece of data on plants, animals, and marine life to create the most complete picture yet of what lives there, how unique it is, and how close many of these species are to disappearing forever.
The findings reveal that Tropical Asia is home to a staggering amount of life. The region, which covers only a small fraction of the Earth's land and ocean surface, harbors nearly one-quarter of all known species on the planet for the groups they studied. This includes about one-fifth of the world's flowering plants and land-dwelling vertebrates, and an even higher proportion of marine life, such as reef-building corals and sharks. What makes this region so special is not just the sheer number of species, but how many of them are unique to it. On average, 85 percent of the species found in these groups are endemic, meaning they are found nowhere else on Earth. This high level of uniqueness is largely driven by the region's geography. Tropical Asia is a complex mosaic of islands, mountain ranges, and ancient land bridges. These natural barriers have isolated populations for millions of years, allowing them to evolve into distinct species. Large islands like Borneo and New Guinea act as evolutionary engines, generating new life forms, while smaller, more isolated islands like Sulawesi hold species that have nowhere else to go.
Despite this incredible wealth of life, the study shows that our knowledge of it is patchy and incomplete. The researchers found that we are still discovering new species at a rapid pace, particularly for amphibians, reptiles, and freshwater fish in areas like South Asia, Indochina, and Borneo. In fact, nearly half of the amphibian species known from South Asia, Indochina, and New Guinea were described in the last twenty-five years. This suggests that the true number of species in these regions is likely much higher than current records show. However, the data we do have is unevenly distributed. While some areas, such as parts of the Malay Peninsula and Taiwan, have been well-sampled, vast stretches of Indonesia, including Sumatra and Kalimantan, remain data deserts. Even in the marine environment, the famous Coral Triangle, known for its incredible diversity, is surprisingly poorly documented compared to neighboring waters. Much of the existing data is also old; for many groups, the average age of a recorded sighting is around fifty years, meaning our understanding of where these animals live is often based on history rather than the present.
This lack of up-to-date information creates a dangerous blind spot for conservation. The researchers analyzed the extinction risk of species using the International Union for Conservation of Nature's Red List, the global standard for assessing how close a species is to disappearing. They found that about one-third of the region's vascular plants, one-fifth of its land and freshwater vertebrates, and almost half of its sharks and rays are threatened with extinction. The situation is even more dire for groups that have been largely ignored by scientists. For many invertebrates, such as insects and spiders, and for most plants, there are no conservation assessments at all. Of the species that have been assessed, a significant portion are classified as "Data Deficient," meaning scientists do not have enough information to know if they are safe or in trouble. Furthermore, many of the existing assessments are outdated, some dating back more than a decade. This is a critical problem because the pressures on these ecosystems have intensified dramatically in recent years. Deforestation for agriculture, the expansion of mining, and the construction of new roads are destroying habitats faster than scientists can update their lists.
The study also highlights a mismatch between what we know and what is happening on the ground. While well-studied groups like birds and mammals often serve as the face of conservation, the paper warns that focusing only on them can be misleading. The threats facing different groups do not always overlap; a forest might be safe for a bird but already destroyed for a specific type of frog or insect. The researchers argue that to protect Tropical Asia's natural heritage, we must move beyond just counting the famous animals. We need to invest heavily in discovering and documenting the countless smaller, less visible species that make up the bulk of the region's biodiversity. This requires expanding research efforts in the data-poor areas, training local scientists, and using new technologies to speed up the process of identification. Without a concerted effort to close these knowledge gaps, we risk losing species before we even know they exist, erasing a quarter of the planet's biological diversity from the face of the Earth.
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