Biodiversity Hotspots: The Last Strongholds of Global Biodiversity

Madagascar, the world's fourth-largest island, was shaped by two great geological events. It first separated from mainland Africa around 170 million years ago, and then broke away from the Indian subcontinent about 90 million years ago. Each split tilted the island's terrain and reshaped its river systems in ways that, according to a 2025 study in Science Advances, acted as a "speciation pump," creating fragmented environments where species evolved independently. This prolonged isolation has created one of Earth's most unique biodiversity hotspots: scientists estimate that around 90% of its mammals and reptiles and more than 80% of its plants exist nowhere else on Earth. Today, the island's extraordinary biodiversity is threatened by deforestation and forest degradation, driven by tavy (a traditional form of slash and burn agriculture). Species are also threatened by hunting and trafficking, invasive species, and climate change.

Home to over 20,000 vascular plant species alone, around 8,000 of which are found nowhere else, the Atlantic Forest is considered one of the world's most critical biodiversity hotspots. Once spanning over 330 million acres, it is also one of the world's most threatened biomes: centuries of agricultural and urban expansion have destroyed nearly 90% of its original vegetation. While around 24% of the biome retains some vegetative cover, only 12.4% of that is mature, protected forest. What remains is highly fragmented, and 97% of those fragments are smaller than 50 hectares. This makes ecological connectivity one of the greatest challenges facing Atlantic Forest biodiversity today.

Stretching from Baja California northward into southwestern Oregon, California's Floristic Province is one of the world's most celebrated biodiversity hotspots. It's home to an estimated 3,500 species of vascular plants, more than 61% of which are found nowhere else on Earth. The region is also home to two of the most iconic trees on the planet: the giant sequoia, the largest living organism on Earth, and its taller but less massive relative, the coastal redwood, both of which listed as Endangered by the IUCN. Threats to this biodiversity hotspot go beyond development and wildfire alone: direct pressures on its ecosystems include urbanization, large-scale agricultural expansion, invasive species, road construction, livestock grazing, logging, and the historical suppression of natural fires. All of these threats are compounded by a changing climate that is intensifying drought and increasing the scale and severity of wildfires.

South Africa's Cape Floristic Region, the world's smallest floral kingdom and one of its greatest biodiversity hotspots, is home to around 9,000 higher plant species, 69% of which are found nowhere else on Earth. Notable plants include the king protea (Protea cynaroides), South Africa's national flower, and Fynbos — a fine-leaved, sclerophyllous shrubland uniquely adapted to the region's Mediterranean climate and periodic fire cycles, on which many of its species depend for regeneration. The greatest threats to the region are land conversion and invasive alien species, alongside increasingly intense and frequent wildfires driven by climate change and the spread of invasive woody plants that raise fuel loads.

The Philippines, an archipelago of more than 7,000 islands in Southeast Asia, is one of the world’s 18 megadiverse countries and a global biodiversity hotspot. It is home to over 50,000 plant species, including more than 3,000 endemic species, and at least 49% of its terrestrial wildlife is endemic. This exceptional biodiversity is under serious pressure from habitat loss, habitat fragmentation, overexploitation, invasive species, pollution, and climate change.

If you’ve ever vacationed in Thailand, you know why this beautiful country has made the list! As one of the most biodiverse countries in Southeast Asia, Thailand is home to around 15,000 plant species, making up 8% of the world's total. Its wildlife includes iconic species such as the Asian Elephant, Sunda Pangolin and Indochinese Tiger. Many species face pressure from illegal hunting, habitat loss, destructive fishing practices, pollution, invasive species, and climate change.