A biodiversity hotspot is a region that holds an exceptionally high number of species found nowhere else on Earth and has already lost a large share of its original habitat. The concept, first proposed by ecologist Norman Myers in 1988 and later refined in 2000, applies a two-part test: the area must contain at least 1,500 species of vascular plants as endemics, and it must have lost 70 percent or more of its original vegetation. Thirty-six regions currently meet these criteria, and together they cover only about 2.5 percent of Earth’s land surface while harboring more than half of all plant species restricted to a single region. That concentration of irreplaceable life in a small, already-damaged footprint is what makes hotspots the sharpest focus for conservation concern.
How the Concept Took Shape
Myers’s original 1988 paper identified ten tropical forest regions where deforestation was threatening large numbers of endemic species. By 2000, a major update expanded the list to 25 hotspots and introduced the formal thresholds for endemism and habitat loss that remain in use. The idea caught on fast. It attracted funding from the MacArthur and Moore Foundations, the World Bank, the Global Environment Facility, and Conservation International, among others, totaling over $750 million committed to hotspot-focused conservation, the largest sum ever directed at a single conservation strategy at the time.1BioScience. Biodiversity Hotspots Revisited The number of recognized hotspots has since grown to 36 as more regions were assessed and additional data accumulated.
The appeal of the hotspot framework is strategic triage. With limited money and political capital, conservation groups needed a way to identify where losing habitat would cause the greatest number of extinctions. The twin criteria of high endemism and severe habitat loss function like a filter: they pick out places where the most irreplaceable species are in the most immediate danger. That logic has guided billions of dollars in spending over three decades.
Why Mountains and Islands Dominate the List
Many of the 36 hotspots are mountainous regions, island archipelagos, or both. Mountains generate biodiversity through a combination of isolation, varied climate zones packed into short vertical distances, and geological upheaval that creates new habitat over evolutionary time. Rugged terrain separates populations of the same species, which over millennia diverge into distinct forms. The interplay of tectonic activity, long-term climate shifts, and complex topography enhances speciation rates while also offering niches where lineages can persist for millions of years.2PubMed. Building mountain biodiversity: Geological and evolutionary processes The climatic complexity of mountain regions differs fundamentally from lowland areas, likely playing a central role in both generating and maintaining high species counts.3PubMed. Humboldt’s enigma: What causes global patterns of mountain biodiversity?
Islands work by a related mechanism. Geographic isolation from the mainland prevents interchange of species, which pushes resident populations toward endemism over time. Oceanic islands formed by volcanism or tectonic movement can spark bursts of adaptive radiation, as colonizing species diversify to fill empty niches. The ocean surrounding these islands also buffers them from the large-scale climate swings that trigger mass extinctions on continents, allowing ancient lineages to survive.4PubMed Central. Islands conserve high species richness and areas of endemism of Hormaphidinae aphids The result is that many island hotspots contain species that have evolved nowhere else and have no close relatives anywhere else, making each extinction there a permanent loss with no backup population.
Not Just Land and Not Just Tropics
The original hotspot framework was designed for terrestrial plants and vertebrates, but the concept has expanded. Marine biologists have identified their own hotspots, particularly coral reefs. An analysis of over 3,200 species of reef fish, corals, snails, and lobsters found that restricted-range species cluster into marine centers of endemism. The ten richest of these centers cover roughly 16 percent of the world’s coral reefs, which itself amounts to a tiny fraction of the ocean, yet they contain between 45 and 54 percent of restricted-range species in the groups studied.5PubMed. Marine biodiversity hotspots and conservation priorities for tropical reefs
The Coral Triangle in Southeast Asia is the most species-rich marine region on Earth, but how it got that way is counterintuitive. Research on coral evolution found that the speciation rate within the Coral Triangle has actually been lower than in surrounding waters, and the extinction rate higher. Its richness persists because species from surrounding regions keep expanding their ranges into the Triangle faster than local species die out.6Evolution. The origin and evolution of coral species richness in a marine biodiversity hotspot The Triangle functions less like a cradle where new species are born and more like a museum that collects species from its neighbors.
Freshwater ecosystems are another overlooked category. Fresh water covers less than one percent of Earth’s surface yet supports roughly 9.5 percent of all known animal species, including about a third of all vertebrates. The species richness of freshwater bony fishes is nearly equal to that of all marine bony fishes, despite the ocean being vastly larger.7Current Biology. What Is a Biodiversity Hotspot and Why Do They Matter? Ancient lakes are particularly striking examples. Lake Ohrid in the Balkans, one of Europe’s oldest lakes, harbors an extraordinary number of species found nowhere else, but decades of pollution and development have created what researchers describe as a “creeping biodiversity crisis.”8Biogeosciences. A freshwater biodiversity hotspot under pressure – assessing threats and identifying conservation needs for ancient Lake Ohrid
What Makes Hotspots Valuable Beyond Their Species Lists
The standard argument for protecting hotspots emphasizes preventing extinctions, but there are practical reasons that go beyond species counts. Forests and other vegetation in hotspot regions store enormous quantities of carbon. A detailed carbon inventory of the Eastern Arc Mountains in Tanzania, a recognized hotspot, estimated the landscape stores about 1.3 billion metric tons of carbon, considerably higher than most previous estimates for the region. Tropical forest there stores roughly 182 metric tons of carbon per hectare.9PubMed Central. Quantifying and understanding carbon storage and sequestration within the Eastern Arc Mountains of Tanzania, a tropical biodiversity hotspot When hotspot forests are cleared, that carbon enters the atmosphere, accelerating climate change.
There is some overlap between areas that are biodiversity hotspots and areas that store the most carbon, but it is far from complete. One global analysis found 38 percent overlap between carbon and biodiversity hotspots in regions targeted for proactive conservation, but only 5 percent overlap in reactive conservation settings.10PubMed Central. Mapping co-benefits for carbon storage and biodiversity to inform conservation policy and action That means protecting biodiversity and protecting carbon stocks are related goals but not the same goal. Some carbon-rich areas are not particularly biodiverse, and some species-rich areas do not store much carbon. Conservation planning benefits from mapping both.
Hotspots are also reservoirs of genetic resources for agriculture and medicine. Morocco, recognized as part of the Mediterranean hotspot, has been identified as a significant center for crop wild relatives, the wild ancestors and cousins of domesticated food plants. These wild species carry genetic traits like drought tolerance and disease resistance that plant breeders need to keep food crops adaptable in a changing climate.11Genetic Resources and Crop Evolution. Crop wild relatives and wild harvested plants of Morocco: checklist and priorities for conservation Losing a hotspot does not just mean losing charismatic animals; it can mean losing the genetic raw material that future agriculture depends on.
The Threats That Define Hotspots
By definition, hotspots have already lost most of their original habitat, but the losses continue. A global analysis of land-use change found that agricultural expansion and urban growth together account for nearly all habitat loss in hotspots, with farming responsible for about 90 percent and urbanization for about 10 percent. The pattern differs by wealth: in developing nations, agricultural expansion drives the damage, with hotspots like Sundaland, Indo-Burma, and the Cerrado especially hard hit. In wealthier countries, urban sprawl plays a larger role, as seen in the North American Coastal Plain and the Forests of East Australia.12Resources, Conservation and Recycling. Hotspots of land-use change in global biodiversity hotspots
Climate change compounds the problem, and endemic species are the most exposed. A meta-analysis of over 8,000 projections across 273 areas of exceptional biodiversity found that all assessed areas face negative impacts from climate change, but endemic species are consistently hit harder. Terrestrial endemics are projected to be roughly 2.7 times more affected than non-endemic native species and about 10 times more affected than introduced species. Among endemic species studied, 34 percent of terrestrial endemics and 46 percent of marine endemics face projected losses exceeding 80 percent due to climate change alone. For island and mountain species, the figures are even more alarming: 100 percent of island endemics and 84 percent of mountain endemics in the analysis were projected to face that level of extinction risk.13Biological Conservation. Endemism increases species’ climate change risk in areas of global biodiversity importance Introduced species, by contrast, appear largely unaffected by climate projections, which means warming reshuffles communities in favor of generalists and invaders.
Climate change threatens freshwater hotspots in specific ways. Modeling of fish species in an Iranian biodiversity hotspot predicted that native species will suffer far more than non-natives, with 13 species losing over 90 percent of their range and seven facing complete loss of suitable habitat.14Scientific Reports. Predicting climate heating impacts on riverine fish species diversity in a biodiversity hotspot region Freshwater species often cannot simply move to cooler areas because they are confined to individual river basins or lake systems, making them especially vulnerable when conditions shift.
Invasive Species and Island Vulnerability
Island hotspots face a particular threat from invasive species. Evolution on islands tends to produce organisms that are well adapted to local conditions but poorly equipped to deal with new competitors, predators, and diseases. Species evolve toward “island syndromes,” including changes in body size, reduced defensive traits, and smaller clutch sizes. These adaptations help them thrive in isolation but make them disproportionately vulnerable once humans introduce rats, cats, goats, or invasive plants.15PubMed Central. Scientists’ warning – The outstanding biodiversity of islands is in peril Global biodiversity loss has been disproportionately rapid on islands, and invasive species are a major driver of those extinctions.16PubMed Central. Globally threatened vertebrates on islands with invasive species
The good news is that invasive species removal on islands is one of conservation’s better success stories. Eradicating rats or feral cats from small islands has led to rapid recoveries of seabird colonies and native vegetation in numerous well-documented cases. The challenge is scale: larger islands with human populations make eradication campaigns far more complex and expensive.
Extinction Debt and the Illusion of Stability
One of the more unsettling concepts in hotspot conservation is extinction debt, the idea that species losses from past habitat destruction have not fully played out yet. When a forest is fragmented, the remaining patches may still hold populations of many species, but some of those populations are too small to survive long-term. The extinctions come years or decades later, creating a false sense that the current habitat is adequate.
Research in Madagascar, one of the hotspots with the highest rates of habitat loss, quantified time-lagged effects of fragmentation for 157 non-flying terrestrial mammal species. The study found that ignoring these delayed effects leads to significant underestimation of the real impact of habitat loss.17PubMed Central. Time-lagged effects of habitat fragmentation on terrestrial mammals in Madagascar Similar work in the Argentine Dry Chaco, a deforestation hotspot in South America, found strong evidence of extinction debt: the landscape structure from the year 2000 predicted current bird and mammal richness better than either current or older landscape data, suggesting that species are responding with a delay of roughly 10 to 25 years.18Journal of Applied Ecology. Mapping extinction debt highlights conservation opportunities for birds and mammals in the South American Chaco
The practical implication is uncomfortable: the species counts you see today in many fragmented hotspots are probably higher than the landscape can actually sustain. Some of those species are already committed to local extinction even if no further habitat is destroyed. Recognizing extinction debt changes the calculus of how urgently remaining fragments need to be reconnected through habitat corridors or restored.
Indigenous Lands and Overlooked Conservation
An increasingly well-documented finding is that Indigenous-managed lands within and near hotspots often retain better environmental quality than surrounding areas. One study found that within biodiversity hotspots, armed conflict was more likely to occur on Indigenous Peoples’ lands than on non-Indigenous lands, yet environmental damage and anthropogenic impacts were both lower on Indigenous lands.19Biological Conservation. Even after armed conflict, the environmental quality of Indigenous Peoples’ lands in biodiversity hotspots surpasses that of non-Indigenous lands That finding held even in areas subjected to active conflict, suggesting that Indigenous land management practices are resilient.
Across Australia, Brazil, and Canada, Indigenous lands showed the highest species richness in all focal vertebrate groups combined, surpassing both formal protected areas and non-protected lands.20Environmental Science & Policy. Vertebrate biodiversity on indigenous-managed lands in Australia, Brazil, and Canada equals that in protected areas This matters because formally protected areas like national parks cover a relatively small fraction of land. In Australia, Indigenous lands represent over half the country’s terrestrial area, compared with about 9 percent for protected areas. Recognizing Indigenous governance as a conservation mechanism, rather than treating conservation as something imposed by outside institutions, could dramatically expand the effective footprint of biodiversity protection.
There is also a striking overlap between biological and linguistic diversity. High-biodiversity regions, including hotspots, account for roughly 70 percent of all languages on Earth, and many of those languages are themselves endemic to particular regions and face extinction.21PubMed Central. Co-occurrence of linguistic and biological diversity in biodiversity hotspots and high biodiversity wilderness areas When communities lose their languages, they often lose the traditional ecological knowledge embedded in those languages, knowledge about local species, seasonal patterns, and land management techniques that may have been sustaining biodiversity for centuries.
Critiques and Blind Spots in the Hotspot Framework
The hotspot concept has been enormously influential, but it has real limitations. One major critique is that the original framework leans heavily on vascular plants and vertebrates as measures of biodiversity, with relatively little attention to invertebrates. Given that insects and other invertebrates make up the vast majority of animal species, critics have pointed out that plants may not reliably serve as umbrella species for herbivorous insects, fungi, and nematodes, and that a more detailed analysis of these groups might shift conservation priorities.22Global Ecology and Conservation. Biodiversity hotspots: A shortcut for a more complicated concept
Another issue is that “hotspot” has become a loosely used term. Researchers now speak of hotspots for species richness, endemism, rare species, threatened species, evolutionary distinctiveness, and functional diversity, and these do not always overlap. An analysis of different diversity metrics found that hotspots based on different components of diversity were largely inconsistent with one another. Loosely collected species generally prevailed, with relatively few distinct assemblages, suggesting that hotspots could be unreliable for directing conservation if based on only one component of diversity.23PubMed Central. What’s hot and what’s not: Making sense of biodiversity ‘hotspots’ A region that ranks as a hotspot for overall species richness might not rank highly for evolutionary uniqueness or functional traits, and vice versa.
The framework also focuses on places that are already severely degraded, which means it inherently directs money toward damaged landscapes. Some conservation biologists argue that protecting large, intact wilderness areas like the Amazon or the Congo Basin would save more total biodiversity per dollar, even though those areas do not qualify as “hotspots” precisely because they have not yet lost 70 percent of their vegetation. The tension between protecting the most threatened places and protecting the most intact ones remains unresolved in conservation planning.
Where the Money Goes
Conservation budgets are perpetually insufficient, which makes allocation decisions life-or-death for species. Research on cost-effective global conservation spending has found that incorporating both the cost of conservation action and the rate of habitat loss into funding decisions matters more than which group of organisms you use to set priorities. About two-thirds of funding goes to the same regions regardless of whether the priority-setting focuses on mammals, birds, amphibians, or plants, as long as cost and threat data are included.24PubMed Central. Cost-effective global conservation spending is robust to taxonomic group Without accounting for threat level and cost, only about one-fifth of funding ends up in the same places.
A return-on-investment approach, one that weighs biological importance against the cost of protecting land and the urgency of the threat, consistently outperforms simpler allocation methods. After 20 years of modeled investment, a return-on-investment strategy protected 32 to 69 percent more plant and vertebrate species than four alternative approaches tested.25PLoS ONE. Protecting Biodiversity when Money Matters: Maximizing Return on Investment The implication is that identifying hotspots is only half the job. Where land is cheap, threats are imminent, and governance allows effective enforcement, a dollar spent can protect many times more species than the same dollar spent in a wealthy nation with high land values and slower rates of loss.
New Tools for Finding and Tracking Biodiversity
The hotspot framework was built on field surveys and museum collections, but the technology for documenting life on Earth has changed dramatically. Environmental DNA sampling, where researchers filter water or soil and sequence the genetic material left behind by organisms, can detect species that traditional surveys miss entirely. Bioacoustic monitoring uses automated recorders and machine-learning algorithms to identify bird, bat, frog, and insect species by their calls. These high-throughput methods, alongside whole-genome sequencing and AI-driven image recognition, are transforming taxonomy from a slow, reactive discipline into something faster and more predictive.26Zoological Synthesis. Modern Taxonomic Tools in the Race Against Anthropogenic Extinction
For hotspots, these tools matter because many of the species within them have never been formally described. Tropical forests and deep reef systems almost certainly harbor thousands of species unknown to science, and some of those species are vanishing before anyone catalogs them. Faster identification methods raise the chance that conservation efforts can target species and habitats before they are lost, rather than documenting losses after the fact.
Does Ecotourism Actually Help
Ecotourism is frequently promoted as a way to give local communities an economic stake in protecting hotspot ecosystems. The logic is appealing: if a standing forest generates more revenue through tourism than a cleared one does through farming, people will choose to protect it. The evidence, however, is mixed. A study using counterfactual analysis in the Himalayan hotspot found limited evidence that ecotourism hubs experienced different forest-loss trajectories than non-ecotourism areas. In Nepal and Bhutan, differences in forest loss between ecotourism hubs and matched comparison areas were not significant. In India, forest loss was actually higher in ecotourism hubs. Only in China, where overall forest loss rates were the highest in the analysis, did ecotourism areas show lower loss rates than non-ecotourism areas.27Conservation Biology. Effects of ecotourism on forest loss in the Himalayan biodiversity hotspot based on counterfactual analyses
None of this means ecotourism is useless. It can still generate income, build local support, and raise international awareness. But the idea that ecotourism alone will save hotspot forests is not well supported. The Himalayan data suggest that tourism revenue has to be quite substantial relative to the alternative economic pressures on land before it changes deforestation trajectories. In places where farming or logging are highly profitable, a modest tourist lodge is not going to tip the balance.