A biodiversity hotspot is a biogeographic region with a significant reservoir of biodiversity that is threatened with destruction.
The concept of biodiversity hotspots was originated by Dr. Norman Myers in two articles in “The Environmentalist” (1988 & 1990). It was later revised after thorough analysis by Dr. Myers and others in the journal Nature (2000) and in the popular book, “Hotspots: Earth’s Biologically Richest and Most Endangered Terrestrial Ecoregions” (2000). The hotspots idea was also promoted as a strategy for biodiversity conservation by Russell Mittermeier and Conservation International in the popular book “Hotspots revisited” (2004), although this book was not subjected to scientific peer-review like the other hotspots analyses.
To qualify as a biodiversity hotspot, a region must meet two strict criteria: it must contain at least 0.5% of the world's plant species as endemics (about 1,500 species), and it must have lost at least 70% of its original habitat. Around the world, at least 25 areas qualify under this definition, with nine others possible candidates. These sites support nearly 60% of the world's plant, bird, mammal, reptile, and amphibian species, with a very high share of those being restricted to a single hotspot.
Hotspot conservation initiatives
Only a small percentage of the total land area within biodiversity hotspots is now protected. Several large international organizations are working in many ways to improve conservation of these regions. Thousands of small local conservation organizations also work to protect these regions and the species surviving within them.
- Critical Ecosystem Partnership Fund (CEPF) is a global program that provides provides funding and technical assistance to nongovernmental organizations and other private sector partners to protect biodiversity hotspots. CEPF has provided support to more than 1,000 civil society groups working locally to conserve hotspots in Africa, Asia, and Latin America. CEPF is a joint initiative of The Global Environment Facility, The John D. and Catherine T. MacArthur Foundation, Agence Française de Développement, Ministry of Finance, Government of Japan, Conservation International and The World Bank. 
- Conservation International (CI) adopted biodiversity hotspots as a main target for conservation efforts. This nongovernmental organization has the stated goal of applying innovations in science, economics, policy and community participation to protect the Earth's richest regions of plant and animal diversity including: biodiversity hotspots, high-biodiversity wilderness areas and important marine regions. CI works in more than 40 countries on four continents, with headquarters near Washington, D.C.
- The World Wildlife Fund (WWF) has derived a system called the “Global 200 Ecoregions”, the aim of which is to select priority Ecoregions for conservation within each of 14 terrestrial, 3 freshwater, and 4 marine habitat types. They are chosen for their species richness, endemism, taxonomic uniqueness, unusual ecological or evolutionary phenomena, and global rarity. While WWF does not specifically target hotspots, all biodiversity hotspots contain at least one of WWF's Global 200 Ecoregion.
- Birdlife International has identified 218 “Endemic Bird Areas” (EBAs), each of which hold two or more bird species found nowhere else. Many of these also occur in biodiversity hotspots. Birdlife has also identified a more refined set of priority areas for conservation known as Important Bird Areas. Many of the more than 7,500 IBAs are in biodiversity hotspots. Important Bird Areas
- Alliance for Zero Extinction is an initiative of a large number of scientific organizations and conservation groups who co-operate to identify specific sites with the most threatened species of the world. They have identified 595 sites thus far. 
- The National Geographic Society has prepared A World map of the hotspots and ArcView shapefile and metadata for the Biodiversity Hotspots including details of the individual endangered fauna in each hotspot, which is available from Conservation International.
The biodiversity hotspots by region
North and Central America
- California floristic province
- Caribbean Islands
- Madrean pine-oak woodlands
- Atlantic Forest
- Chilean Winter Rainfall-Valdivian Forests
- Tropical Andes
Europe and Central Asia
- Mediterranean Basin
- Mountains of Central Asia
- Cape Floristic Region
- Coastal forests of eastern Africa
- Eastern Afromontane
- Guinean Forests of West Africa
- Horn of Africa
- Coastal Forests of Eastern Africa
- Madagascar and the Indian Ocean Islands
- Succulent Karoo
- East Melanesian Islands
- Eastern Himalaya
- Mountains of Southwest China
- New Caledonia
- New Zealand
- Southwest Australia
- Western Ghats and Sri Lanka
Critiques of Hotspots
The high profile of the biodiversity hotspots approach has resulted in considerable criticism. Papers such as Kareiva & Marvier (2003)  have argued that the biodiversity hotspots:
- Do not adequately represent other forms of species richness (e.g., total species richness or threatened species richness).
- Do not adequately represent taxa other than vascular plants (e.g., vertebrates or fungi).
- Do not protect smaller scale richness hotspots.
- Do not make allowances for changing land use patterns. Hotspots represent regions that have already experienced considerable habitat loss, but this does not mean they are experiencing ongoing habitat loss. On the other hand, regions that are relatively intact (e.g., the Amazon Basin) have experienced relatively little land loss, but are currently losing habitat at tremendous rates.
- Do not protect ecosystem services.
- Do not consider phylogenetic diversity.
A recent set of papers has pointed out that biodiversity hotspots may differ substantially depending on how one measures biodiversity . Another criticism is that hotspots (and many other sets of priority regions) do not address the concept of cost, which can vary by orders of magnitude across the world . The purpose of biodiversity hotspots is not simply to identify regions with high biodiversity value, but to prioritize conservation spending. The regions identified include regions in the developed world (e.g., the California Floristic Province), alongside regions in the developing world (e.g., Madagascar). The cost of land is likely to vary tremendously between these regions, but the biodiversity hotspots do not explicitly consider this difference.
- Myers, N. 1988. Threatened biotas: `hotspots' in tropical forests. Environmentalist 8, 187-208
- Myers, N. 1990. The biodiversity challenge: expanded hotspots analysis. Environmentalist 10, 243-256
- Myers, N., R. A. Mittermeier, C. G. Mittermeier, G. A. B. da Fonseca, and J. Kent. 2000. Biodiversity hotspots for conservation priorities. Nature 403:853-858
- The Critical Ecosystem Partnership FundOfficial website
- About Conservation International, retrieved 10/23/2007CI's Mission
- Alliance for Zero ExtinctionOfficial website
- Conservation International (2007) BIODIVERSITY HOTSPOTS Resources
- Kareiva, P. and M. Marvier (2003) Conserving Biodiversity Coldspots, American Scientist 91:344-351.
- Orme et al. (2005) Global hotspots of species richness are not congruent with endemism or threat, Nature 436:1016-1019.
- Possingham, H. and K. Wilson (2005) Turning up the heat on hotspots, Nature 436:919-920.