More species evolved here than almost anywhere on Earth. Genetic analysis shows glaciers repeatedly isolated populations on different peaks, driving rapid evolution.
Kogo, CC BY-SA 3.0, via Wikimedia Commons
A Cradle of Speciation
The Hengduan Mountains of southwest China are one of the most diverse temperate regions on the planet. This geological region, covering about 500,000 square kilometers, contains an estimated 12,800 species of seed plants, which is over 42% of China's total. Of these, at least 3,300 species are endemic, meaning they are found nowhere else on Earth. The region's alpine zone alone holds between two and three times more seed plant species than any other alpine belt in the world.
The mountains are a series of massive north-south ranges at the southeastern edge of the Tibetan Plateau. Major rivers like the Yangtze (Jinsha), Mekong (Lancang), and Salween (Nu) have carved some of the deepest and most dramatic parallel gorges on Earth. In some places, the shortest distance between the Mekong and the Salween is less than 19 kilometers, yet they are separated by towering mountain barriers. This extreme topography creates a vast range of habitats, from subtropical valleys to alpine peaks reaching over 6,000 meters (19,700 feet), and is a primary cause of its extraordinary biodiversity.
The Glacial Species Pump
The cause of this incredible species generation is a process of repeated isolation and evolution driven by ancient climate change. The formation of these mountains, resulting from the collision of the Indian and Eurasian tectonic plates, created the necessary vertical landscape. Then, during the repeated glacial cycles of the Pleistocene epoch (roughly 2.6 million to 11,700 years ago), a process known as allopatric speciation occurred on a massive scale.
As glaciers advanced, they flowed down the valleys, forcing plant and animal populations into isolated high-altitude refuges on different mountain peaks. Separated from their relatives, these small populations began to diverge genetically. When the climate warmed and the glaciers retreated, the populations could expand again, but they were often so different they could no longer interbreed. This cycle of fragmentation and isolation happened repeatedly, creating a "species pump" that rapidly generated new and distinct forms of life. This process is seen in plant genera like Rhododendron, Gentiana, and Primula, which show explosive diversification in the region. For example, 30-50% of the world's perhaps 1000 Rhododendron species are found here.
💡Fun Facts
The Hengduan Mountains are the original home of many common garden flowers, including some geraniums, lilies, and lady slipper orchids.
The shortest distance between the Mekong River and the Jinsha (Yangtze) River in this region is just 66 kilometers (about 41 miles).
The area hosts 16 genera of plants that have over 100 distinct species each, most of which formed within this region.
The Nu River Gorge, carved by the Salween, can reach an average depth of 2,000 meters (6,562 feet) and is nicknamed the "Oriental Grand Gorge."
The mountain range is a vast region. Access to specific parks and reserves varies.
Admission
Varies by park; many areas are free to access, while specific sites like Yading Nature Reserve or Pudacuo National Park require entrance fees.
Accessibility
The terrain is extremely mountainous and rugged. Travel often involves narrow, winding mountain roads. Hiking trails can be steep and are at high elevations.
