A biodiversity hotspot is an area where many different plants and animals live, but it is at risk because of human activities. Norman Myers first described the idea in two articles in The Environmentalist in 1988 and 1990. Later, after detailed studies by Myers and others, the concept was updated in a book titled Hotspots: Earth's Biologically Richest and Most Endangered Terrestrial Ecoregions and a paper in the journal Nature, both published in 2000.

To be classified as a biodiversity hotspot in Myers’ 2000 map, a region must meet two requirements: it must have at least 1,500 species of vascular plants (more than 0.5% of the world’s total) that are found only in that area, and it must have lost at least 70% of its natural forests and plants. Globally, 36 areas meet these conditions. These hotspots are home to nearly 60% of the world’s plant, bird, mammal, reptile, and amphibian species, with many of these species being found only in those regions. Some hotspots contain up to 15,000 species of plants that are unique to the area, and some have lost up to 95% of their natural habitat.

Biodiversity hotspots have many different ecosystems but cover only 2.4% of Earth’s surface. Myers originally identified 10 hotspots, but the current list includes 36 areas that once covered more than 15.7% of Earth’s land. However, these regions have lost about 85% of their area due to habitat destruction. This loss of habitat explains why about 60% of Earth’s land-based life lives on just 2.4% of Earth’s surface. Caribbean Islands such as Haiti and Jamaica are experiencing major challenges for their unique plants and animals because of fast-paced deforestation. Other areas, including the Tropical Andes, Philippines, Mesoamerica, and Sundaland, may lose most of their plant and animal species if deforestation continues at the current rate.

Hotspot conservation initiatives

Only a small part of the land in biodiversity hotspots is currently protected. Many international groups work to help protect these areas.

• The Critical Ecosystem Partnership Fund (CEPF) is a global program that gives money and help to organizations that protect Earth’s most diverse areas for plants and animals, including biodiversity hotspots, wilderness areas with high biodiversity, and important marine regions.
• The World Wide Fund for Nature created a system called the "Global 200 Ecoregions," which helps choose areas important for conservation based on fourteen types of land, three types of freshwater, and four types of marine habitats. These areas are selected because they have many species, species found only in one place, unique species, unusual natural events, or rare ecosystems. Every biodiversity hotspot includes at least one of these selected areas.
• BirdLife International has identified 218 "Endemic Bird Areas" (EBAs), each of which has two or more bird species that live nowhere else. BirdLife International also identified more than 11,000 Important Bird Areas worldwide.
• PlantLife International helps organize programs to find and manage Important Plant Areas.
• The Alliance for Zero Extinction is a group of scientists and conservationists who work together to protect the most endangered species that live only in specific places. This group has identified 595 sites, many of which are BirdLife’s Important Bird Areas.
• The National Geographic Society created a world map of hotspots and shared data, including details about endangered animals in each hotspot, through Conservation International.
• The Compensatory Afforestation Management and Planning Authority (CAMPA) works to stop the destruction of forests in India.

Distribution by region

Most biodiversity is found in the tropics, and most biodiversity hotspots are also in the tropics. Out of 34 biodiversity hotspots, 15 are classified as old, protected from extreme weather changes, and infertile landscapes (OCBILs). These areas were historically separated from other climate zones, but recent human activities and expansion have made them vulnerable. OCBILs were mainly threatened by the movement of indigenous groups and military actions, as the poor soil previously discouraged human settlement. Conservation efforts for OCBILs in biodiversity hotspots are gaining attention because they support high biodiversity, stable species lineages, and may have high potential for future species development. These areas are stable and can be called refugia.

North and Central America
• California Floristic Province (8)
• Madrean pine–oak woodlands (26)
• Mesoamerica (2)
• North American Coastal Plain (36) — includes the Atlantic Plain and Gulf Coastal Plain
• Caribbean Islands (3)

South America
• Atlantic Forest (4)
• Cerrado (6)
• Chilean Winter Rainfall-Valdivian Forests (7)
• Tumbes–Chocó–Magdalena (5)
• Tropical Andes (1)

Europe and Eurasia
• Mediterranean Basin (14)
• Caucasus (15)
• Irano-Anatolian (30)

Africa
• Cape Floristic Region (12)
• Coastal Forests of Eastern Africa (10)
• Eastern Afromontane (28)
• Guinean Forests of West Africa (11)
• Horn of Africa (29)
• Madagascar and the Indian Ocean Islands (9)
• Maputaland-Pondoland-Albany (27)
• Succulent Karoo (13)

Asia
• Mountains of Central Asia (31)
• Himalaya (32)
• Indo-Burma (19)
• Western Ghats and Sri Lanka (21)

Southeast Asia and Asia-Pacific
• East Melanesian Islands (34)
• New Caledonia (23)
• New Zealand (24)
• Philippines (18)
• Polynesia-Micronesia (25)
• Eastern Australian temperate forests (35)
• Southwest Australia (22)
• Sundaland, Indonesia, and Nicobar Islands of India (16)
• Wallacea of Indonesia (17)

• Japan (33)
• Mountains of Southwest China (20)

Criticism

The popularity of the biodiversity hotspots approach has led to some criticism. Papers such as Kareiva & Marvier (2003) noted that biodiversity hotspots (and many other areas chosen for protection) do not take into account the cost and do not consider phylogenetic diversity.