Biodiversity Hotspots: 36 Regions, 60% of Endemic Species, 2.4% of Earth's Land

Two Point Four Percent of Land. Sixty Percent of Species.

Norman Myers, a British environmentalist, published a paper in The Environmentalist in 1988 that identified 10 tropical forest regions where plant species diversity and threat from human activity were both extraordinarily high. He called them "hotspots." In a 2000 follow-up paper published in Nature, Myers expanded the analysis to 25 hotspots using two strict quantitative criteria: at least 1,500 endemic vascular plant species (plants found nowhere else on Earth) and having lost at least 70% of their original primary vegetation. These 25 regions together covered only 1.4% of Earth's land surface yet contained more than 60% of all endemic plant species and large proportions of endemic vertebrates. Conservation International adopted the hotspot framework as an organizing concept for global conservation priority-setting, eventually recognizing 36 hotspots covering approximately 2.4% of Earth's land area.

The Two-Part Definition

The hotspot criteria combine biological richness with threat — neither alone qualifies a region. An extremely species-rich region with intact habitat is a biodiversity wilderness, not a hotspot. A heavily degraded region with few species doesn't qualify either. The specific criteria require:

• At least 1,500 endemic vascular plant species — meaning species found in that hotspot and nowhere else on Earth. This threshold represents roughly 0.5% of all known vascular plant species in a single geographic region.
• At least 70% of original primary vegetation already lost to human activity — documenting that the region is genuinely threatened, not merely species-rich.
• The combination of these two conditions creates a conservation triage logic: greatest return on conservation investment comes from protecting areas where irreplaceable species face extinction most urgently.
• Vertebrate endemism often tracks plant endemism closely, meaning plant-defined hotspots also capture exceptional concentrations of endemic birds, mammals, reptiles, and amphibians.

The 36 Hotspots: Where They Are

The 36 recognized hotspots span tropical and subtropical regions on five continents, with concentrations in island systems and mountain ranges where geographic isolation has driven high endemism. The Mediterranean Basin — including southern Europe, North Africa, and the Levant — is the only hotspot in the temperate zone of the Northern Hemisphere, qualifying due to its exceptional endemic flora (approximately 13,000 endemic plant species) and centuries of agricultural and urban transformation.

The Tropical Andes: The Richest Hotspot

The Tropical Andes hotspot is the most biodiverse region on Earth by virtually every metric. Spanning the Andean mountain system from Venezuela south through Colombia, Ecuador, Peru, and Bolivia to northern Argentina, the region encompasses extraordinary altitudinal gradients — from Amazonian lowland jungle at sea level to Andean peaks above 6,000 meters — that create hundreds of distinct microclimates and ecological niches within short horizontal distances. The hotspot contains approximately 20,000 endemic plant species — roughly 6% of all plants on Earth in 1.6% of Earth's land area. Bird diversity exceeds 1,700 species, including more than 600 endemics. Amphibian endemism is particularly striking: the Andes contain more endemic amphibian species than any other hotspot, with new species still being described annually. Chytrid fungus (Batrachochytrium dendrobatidis), habitat loss, and climate change together represent existential threats to Andean amphibian diversity.

Why Islands and Mountains Dominate

Geographic isolation is the primary driver of endemism. Islands — whether oceanic islands surrounded by water or sky islands (mountain ranges surrounded by unsuitable lowland habitat) — restrict species movement and allow evolutionary divergence over time. Madagascar separated from Africa approximately 88 million years ago and from India approximately 80 million years ago, giving its flora and fauna 80+ million years of isolated evolution. The result: 90% of Madagascar's terrestrial fauna is endemic, including all 100+ lemur species, all of its land bird genera, and the majority of its reptiles. The Tropical Andes are a sky island system: different valleys and altitudinal zones are isolated from each other by physical barriers, replicating the island dynamic across a continuous mountain chain.

• The Cape Floristic Region in South Africa supports the most extraordinary endemic flora per unit area of any hotspot: 6,210 endemic plant species in an area smaller than Portugal.
• California Floristic Province hotspot contains the giant sequoia (Sequoiadendron giganteum), the California condor, and approximately 8,000 plant species of which 61% are endemic.
• Hotspots contain approximately 50% of the world's endemic vertebrate species — birds, mammals, reptiles, and amphibians found nowhere else.

Conservation Investment and Effectiveness

The hotspot framework has channeled several billion dollars in conservation funding since Conservation International formally adopted it in 1989. The Critical Ecosystem Partnership Fund (CEPF), established in 2000 as a joint initiative of Conservation International, the Global Environment Facility, and others, has invested more than $800 million in hotspot conservation. Critics of the hotspot approach have noted that prioritizing regions based on endemism may underweight regions like Amazonia — not technically a hotspot because intact vegetation remains above 70% — that contain enormous absolute diversity and carbon storage value. Defenders respond that the hotspot framework is not meant to be the only conservation priority-setting tool but rather an efficient system for identifying where marginal conservation dollars prevent the most irreversible loss.

Hotspots and Human Well-Being

Biodiversity hotspots disproportionately overlap with regions of high human population density and poverty. More than 2 billion people live within the boundaries of the 36 recognized hotspots. Many of these communities depend directly on ecosystem services — freshwater from mountain watersheds, soil fertility maintained by native biodiversity, forest products, fisheries — that intact biodiversity supports. This overlap means that conservation failures in hotspots are not simply species extinctions; they are losses of the ecological infrastructure that supports human livelihoods, water security, and food production for billions of people who are among the world's least economically resilient.