Biodiversity hotspots revealed

Posted: 2 March 2001

Author: Russell Mittermeier, Ian Bowles and William Konstant

Author Info: Russel Mittermeier is President of Conservation International and Chairman of the Primate Specialist Group of IUCN's Species Survival Commission. Ian Bowles is Vice President of Policy and Bill Konstant is Special Projects Director with Conservation International. Conservation International is working with Norman Myers on refining and expanding the hotspots analysis. This article represents a preliminary account of their findings.

US-based Conservation International has completed an updated version of its Global Biodiversity Hotspots map - showing areas of key importance in the battle to save the planet's diversity of life. Here, Russell Mittermeier, Ian Bowles and William Konstant explain what the map reveals and how it can be used to develop a global conservation strategy.

The Earth's 25 biodiversity hotspot regions collectively cover about two per cent of the planet's land surface, yet claim more than 50 per cent of all terrestrial species diversity. Over the next few decades, focusing conservation efforts on these areas can achieve maximum impact for each dollar spent.

Male Panther Chameleon, Madagascar © Kevin Schafer/Still PicturesDr Norman Myers coined the phrase "biodiversity hotspots" in 1988, identifying 10 tropical rainforest hotspots containing an estimated 13 per cent of all plant diversity in just 0.2 per cent of the planet's total land area. In a subsequent analysis, he added several rainforest areas and four Mediterranean-type ecosystems resulting in a total of 18 areas that accounted for 20 per cent of global plant diversity in just 0.5 per cent of the land area.

In 1989, Conservation International (CI) and the MacArthur Foundation were the first organisations to adopt Myers' hotspots as the guiding principle for conservation investment, with CI slightly modifying and expanding Myers' list.

The current analysis is based on species numbers, using vascular plants (300,000 species worldwide) as the principal indicator of biological diversity. Hotspots are identified by two main criteria: first plant endemism and then degree of threat. In this analysis, we have identified regions with 0.5 per cent or more of total global plant diversity represented as endemic species - each region having a minimum of 1,500 plant species. The areas ultimately identified by this analysis have all lost an estimated 75 per cent or more of their original pristine vegetation, with many of the areas on the final hotspots list in fact having already lost 80 to 95 per cent. Thus far, our analysis focuses only on the terrestrial realm.

We have also looked at patterns of diversity and endemism for mammals, birds, reptiles, and amphibians in the target ecosystems. Not surprisingly, the tropical rainforest hotspots generally have very high vertebrate diversity and endemism, following global trends of plant diversity. In contrast, temperate hotspots like the Mediterranean-type ecosystems and drier tropical hotspots, though very high in plants, tend to exhibit much lower vertebrate diversity and endemism.

Endemic species

Endemism is the principal criterion for hotspot status because endemic species are entirely dependent on a single area for survival, and by virtue of their more restricted ranges, are often the most vulnerable. These species confined to highly threatened ecosystems will almost certainly be the first to be hit by extinction episodes, and are most in need of rapid and effective conservation action.

We believe that biodiversity priority setting exercises must focus first and foremost on biological parameters. Threat analysis should come next, highlighting the urgency of conservation action. If we are to have a real impact on biodiversity conservation worldwide, we must emphasise the biologically most important regions regardless of their political or social situation, and do whatever possible to overcome obstacles that might stand in our way.butterflyButterfly, Asia© J Y Gropas/Still Pictures This is not a trivial consideration. New Caledonia in the Pacific, for example, has been grossly under-funded relative to its global biological importance because of its political status as part of a G-7 country (France). Costa Rica, on the other hand, has received proportionately much more support than other comparably important countries because it has, to its credit, created a very receptive, positive environment for international conservation investment.

Based on our method, the first 25 high priority terrestrial biodiversity hotspots have been identified. Of these, five are entirely tropical rainforest areas; five include tropical rainforest and tropical dry forest components; five include tropical rainforest, dry forest and arid systems; five are temperate Mediterranean-type ecosystems; one is a mosaic of dry forests and savannahs; three contain temperate forest and steppe; and one is an arid region.
The Guinean forests of West Africa are home to at least 9,000 plant species, 551 mammals, 514 birds, 135 reptiles and amphibians, and more than 750 butterflies.In all, the remaining natural vegetation in these 25 hotspots covers only about 2 per cent of the land surface of the planet, and yet they have within them a phenomenal total of 131,399 plant species, or 43.8 per cent of all plant diversity represented as endemics. Of course, these areas also harbour many other non-endemics as well.

Although the analysis of the vertebrate data is not yet complete, we estimate that these same areas will encompass the distribution of between 30 to 40 per cent of all terrestrial vertebrates as endemics. Considering total diversity, we also conservatively estimate that these 25 hotspots will contain no less than 50 per cent of all terrestrial biodiversity in only about 2 per cent of the land surface of the planet and possibly much more. Furthermore, our data provides clear indications that at least 75 per cent of terrestrial animal species in the critically endangered, endangered and vulnerable categories, defined by IUCN for globally threatened species, are found within this extremely reduced extent of land.

Among the hotspots, there are top priorities that can sharpen our focus still further. For example, the Tropical Andes hotspot has 20,000 plant species, or 6.7 per cent of the global total, endemic to it, whereas the Mediterranean Basin, a non-tropical hotspot, accounts for 13,000 plant species, or 4.3 per cent of global plant diversity, as endemics. The top 10 hotspots for plant endemism, harbouring 5,000 or more species as endemics, account for 93,218 plant species, or 31.4 per cent of total global plant diversity, as endemics. Again, total diversity in such areas is much higher than what is represented by the endemics alone. The Andes hotspots tops nearly all other hotspots in terms of species diversity and uniqueness. Some 45,000 to 50,000 plant species (18-20 per cent of the world's plants) occur in the Tropical Andes hotspot. Of these 20,000 species can be found else where.

Tropical diversity

In addition to biodiversity hotspots, major tropical wilderness areas also represent high-biodiversity ecosystems, but they are on the opposite end of the threat spectrum. The hotspots consist mainly of heavily exploited and often highly fragmented ecosystems greatly reduced in extent, with usually less than 25 per cent of original pristine vegetation remaining. The major tropical wilderness areas, on the other hand, are still largely intact, with more than 75 per cent of original pristine vegetation remaining, and have low human population density. Most are found in the southern Guianas, southern Venezuela and adjacent parts of extreme northern Brazilian Amazonia, parts of upper Amazonian Brazil, Colombia, Ecuador, Peru, and Bolivia; parts of the Congo Basin, and much of the island of New Guinea.

The major tropical wilderness areas represent important storehouses of biodiversity and major watersheds, and play a vital role in climate stability. They are very often the last places where indigenous peoples have any hope of maintaining their traditional lifestyles, and they will serve as controls against which to measure the management of the more devastated hotspots. Major tropical wilderness areas are also likely to assume even greater recreational, aesthetic, and spiritual values on an increasingly overcrowded planet.

Once we have determined the globally most important hotspots and wilderness areas, we can proceed with the next steps in what we refer to as the hierarchy of priority setting (global, regional, national, local and specific priority sites). Fortunately, a great deal of this more specific priority setting has taken place simultaneously with (and has been heavily stimulated by) various global priority setting processes over the past decade. All of these have considerable agreement.

For instance, if one compares the most critical of the World Wildlife Fund's Global 200 Eco-regions, the most important Endemic Bird Areas of BirdLife International, and the WWF/IUCN Centres of Plant Diversity, with CI's Biodiversity Hotspots, the same regions usually rise to the top, among them the Tropical Andes, Madagascar, the Atlantic Forest Region of Eastern Brazil, the Mesoamerican Forests, the Philippines, most of Indonesia, the Cape Floristic Region of South Africa, and New Caledonia.

In any case, the original message of Myers' hotspots analysis echoes loud and clear: a very high percentage of global terrestrial biodiversity can be protected in a very small portion of Earth's land surface, and international efforts to conserve terrestrial biodiversity should focus heavily, but not exclusively, on these areas.

Now we must agree on the most important and collaborative action to ensure that as much as possible is conserved.

  • A $150,000 fund to help safeguard 25 of the most threatened hotspots was launched in August 2000 as a joint initiative of Conservation International, the World Bank and the Global Environment Facility (GEF). It was planned to spend this money over five years, with the initial focus on hotspot regions of Madagascar, West Africa, and the Tropical Andes.