What is Biodiversity Hotspot? Why is India Considered as a Mega Biodiversity Hotspot?

What is Biodiversity Hotspot?

A biodiversity hotspot is a biogeographic region with significant levels of biodiversity that is threatened by human habitation. Norman Myers wrote about the concept in two articles in “The Environmentalist” (1988), and in 1990 revised after thorough analysis by Myers and others “Hotspots: Earth’s Biologically Richest and Most Endangered Terrestrial Ecoregions” and a paper published in the journal Nature.

To qualify as a biodiversity hotspot on Myers 2000 edition of the hotspot-map, a region must meet two strict criteria: it must contain at least 0.5% or 1,500 species of vascular plants as endemics, and it has to have lost at least 75% of its primary vegetation. Around the world, 36 areas qualify under this definition. These sites support nearly 60% of the world's plant, bird, mammal, reptile, and amphibian species, with a very high share of those species as endemics. Some of these hotspots support up to 15,000 endemic plant species and some have lost up to 95% of their natural habitat.

Biodiversity hotspots host their diverse ecosystems on just 2.4% of the planet's surface, however, the area defined as hotspots covers a much larger proportion of the land. The original 25 hotspots covered 11.8% of the land surface area of the Earth. Overall, the current hotspots cover more than 15.7% of the land surface area but have lost around 85% of their habitat. This loss of habitat explains why approximately 60% of the world's terrestrial life lives on only 2.4% of the land surface area.

Biodiversity hotspot

  • A biodiversity hotspot is a biogeographic region that is both a significant reservoir of biodiversity and is threatened with destruction.
  • The term biodiversity hotspot specifically refers to 25 biologically rich areas around the world that have lost at least 70 percent of their original habitat.
  • The remaining natural habitat in these biodiversity hotspots amounts to just 1.4 percent of the land surface of the planet, yet supports nearly 60 percent of the world's plant, bird, mammal, reptile, and amphibian species.

Why is India Considered as a Mega Biodiversity Hotspot?

A biodiversity hotspot is a biogeographic region with a significant reservoir of biodiversity that is under threat from humans. A hotspot is an area that faces a serious threat from human activities and supports unique biodiversity (endemic, threatened, rare species) with representatives of evolutionary speciation and extinction.

Biodiversity Hotspots Worldwide, The concept of biodiversity was given by Norman Myers (1988).

To qualify as a biodiversity hotspot on Myers 2000 edition of the hotspot map, a region must meet two strict criteria:

1. It must contain at least 0.5% or 1500 species of vascular plants of the world.

2. It has to have lost at least 70% of its primary vegetation.

Myers originally recognized 25 hotspots but recently Conservation International has added 9 more biodiversity hotspots which makes the present number 34. These sites support nearly 60% of the world’s plant, bird, mammal, reptile, and amphibian species, with a very high share of endemic species.

Hotspots in India:

India has two major hotspots. The rate of deforestation in these areas is very high and ecosystems have reached a fragile stage.

1. The Western Ghats:

About the region:

The Western Ghats are a chain of hills that run along the western edge of peninsular India. They are also known as Sahyadri Mountains. They receive high rainfall. It run parallel to the west coast of India and constitutes more than 1600 km strip of forests in the states of Maharashtra, Goa, Karnataka, Tamil Nadu and Kerala.


These regions have moist deciduous forests and rainforests. The region shows high species diversity as well as high levels of endemism. There are over 6000 vascular plants belonging to over 2500 genera in this hotspot, of which over 3000 are endemic.

Much of the world’s spices such as black pepper and cardamom have their origins in the Western Ghats. Many economically important plants such as banana, rice, ginger, etc. have spread to other parts of the country from here.


Nearly 77% of the amphibians and 62% of the reptile species found here are found nowhere else. The region also harbors over 450 bird species, about 140 mammalian species, 260 reptiles, and 175 amphibians. Over 60% of the reptiles and amphibians are completely endemic to the hotspot. Remarkable as this diversity is, it is severely threatened.

India Hotspot-Western Ghats

2. The Eastern Himalayas:

About the region:

The Eastern Himalayas is the region encompassing Bhutan, northeastern India, and southern, central, and eastern Nepal. The region is geologically young and shows high altitudinal variation. Together, the Himalayan mountain system is the world’s highest, and home to the world’s highest peaks, which include Mount Everest and K2.


There are an estimated 10,000 species of plants in the Himalayas, of which one-third are endemic and found nowhere else in the world. Five families —Tetracentraceae, Hamamelidaceae, Circaesteraceae, Butomaceae, and Stachyuraceae — are completely endemic to this region.

Many plant species are found even in the highest reaches of the Himalayan Mountains, For example, a plant species Ermania himalayensis was found at an altitude of 6300 meters in the northwestern Himalayas.


Few threatened endemic bird species such as the Himalayan Quail, Cheer pheasant. Western tragopan is found here, along with some of Asia’s largest and most endangered birds such as the Himalayan vulture and White-bellied heron.

The Eastern Himalayan hotspot has nearly 163 globally threatened species including the One-horned Rhinoceros (Rhinoceros unicornis), the Wild Asian Water buffalo (Bubalus bubalis) and in all 45 mammals, 50 birds, 17 reptiles, 12 amphibians, 3 invertebrates,s, and 36 plant species. The Relict Dragonfly (Epiophlebia Laidlaw) is an endangered species found here with the only other species in the genus being found in Japan.

Indian Hotspot-Eastern Himalayas

Threats to Biodiversity:

Increasing population pressure and over-exploitation of the biotic resources are taking their toll on biodiversity leading to its loss. The major threats to biodiversity decline are land-use changes, pollution, changes in atmospheric CO2 concentrations, changes in the nitrogen cycle and acid rain, climate alterations, and the introduction of exotic species, all coincident to human population growth.

For rainforests, the primary factor is land conversion. Climate will probably change least in tropical regions, and nitrogen problems are not as important because growth in rainforests is usually limited more by low phosphorus levels than by nitrogen insufficiency.

The introduction of exotic species is also less of a problem than in temperate areas because there is so much diversity in tropical forests that newcomers have difficulty becoming established.

Let us consider some of the major causes and issues related to threats to biodiversity:

1. Habitat destruction:

As recently as 30 years ago, most of the regions in these biodiversity hotspots were inaccessible and remote. Now, due to better infrastructure, contact of these areas with humans has increased. Activities such as logging of wood increased agriculture, increased human habitation has led to the destruction of forests and the pollution of rivers.

These factors are causing species ranges to reduce and habitats to become choppy. The government planned to establish habitat corridors, but these plans have not yet materialized in most areas. Activities such as mining, construction of large dams, highway construction has also caused significant destruction of habitats.

2. Resource mismanagement:

Increased tourism without proper regulation has led to pollution and environmental degradation. Prime examples are pilgrimage destinations like Rishikesh and hill stations like Dehradoon.

These spots, once nestled in the pristine ranges of the Himalayas, are now dirty commercial destinations. Places like Dehradoon are even experiencing a construction boom so large that illegal immigrants from Bangladesh are also flocking there.

3. Poaching:

Large mammals such as the tiger, rhinoceros, and elephant once faced the distinct possibility of complete extinction due to rampant hunting and poaching. However, efforts by conservationists since the 1970s have helped stabilize and grow these populations. Still, the trade-in of tiger hides, elephant tusks, tiger teeth, and rhinoceros horn remains profitable and rampant.

4. Global Warming:

There is recent evidence that climate changes are having effects on tropical forest ecology. Warming in general (as distinct from the effects of increasing concentrations of CO2 and other greenhouse gases) can increase primary productivity, yield new plant biomass, increase organic litter, and increase food supplies for animals and soil flora (decomposers).

Temperature changes can also alter the water cycle and the availability of nitrogen and other nutrients. Basically, the temperature variations which are now occurring affect all parts of forest ecosystems, some more than others. These interactions are unimaginably complex.

While warming may at first increase net primary productivity (NPP), in the longer run, because plant biomass is increasing, more nitrogen is taken up from the soil and sequestered in the plant bodies. This leaves less nitrogen for the growth of additional plants, so the increase in NPP over time (due to a rise in temperature or CO2 levels) will be limited by nitrogen availability.

The same is probably true of other-mineral nutrients. The consequences of warming-induced shifts in the distribution of nutrients will not be seen| rapidly, but perhaps only over many years. These events may affect changes] in species distribution and other ecosystem processes in complex ways.

We know little about the reactions of tropical forests, but they may differ from those of temperate forests. In tropical forests, warming may be more important because of its effects on evapotranspiration and soil moisture levels than because of nutrient redistribution.

The migratory patterns of some birds which live in both tropical and temperate regions during the year seem to be shifting, which is dangerous for these species, as they may arrive at their breeding or wintering grounds at an inappropriate time.

Or they may lose their essential interactions with plants which they pollinate or their insect or plant food supplies. Perhaps for these reasons, many migratory species are in decline, and their inability to coordinate migratory clues with climatic actualities may be partly to blame.

Also, as temperatures rise, some bird populations have shifted, with lowland and foothill species moving into higher areas. The consequences for highland bird populations are not yet clear. And many other organisms, both plant and animal, are being affected by warming.

An increase in infectious diseases is another consequence of climate change since the causative agents are affected by humidity, temperature change, and rainfall. Many species of frogs and lizards have declined or disappeared, perhaps because of the increase in parasites occasioned by higher temperatures.

As warming continues, accelerating plant growth, pathogens may spread more quickly because of the increased availability of vegetation (a “density” effect) and because of increased humidity under heavier plant cover. As mentioned above, the fungus Phytophthora cinnamon has demolished many Eucalyptus forests in Australia.

In addition, the geographical range of pathogens can expand when the climate moderates, allowing pathogens to find new, and non-resistant hosts. On the other hand, a number of instances of amphibian decline seem to be due to infections with fungi, which flourish at cooler temperatures.

5. Forest Fragmentation:

The fragmentation of forests is a general consequence of the haphazard logging and agricultural land conversion which is occurring everywhere, but especially in tropical forests.

When forests are cut into smaller and smaller pieces, there are many consequences, some of which may be unanticipated:

(i) Fragmentation decreases habitat simply through loss of land area, reducing the probability of maintaining effective reproductive units of plant and animal populations. Most tropical trees are pollinated by animals, and therefore the maintenance of adequate pollinator population levels is essential for forest health.

When a forest becomes fragmented, trees of many species are isolated because their pollinators cannot cross the unforested areas. Under these conditions, the trees in the fragments will then become inbred and lose genetic variability and vigor.

Other species, which have more wide-ranging pollinators, may suffer less from fragmentation. Most species are not so tolerant, however. Animals, particularly large ones, cannot maintain themselves in small fragmented forests.

Many large mammals have huge ranges and require extensive areas of intact forest to obtain sufficient food or to find suitable nesting sites. Additionally, their migrations may be interrupted by fragmentation.

These animals are also much more susceptible to hunting in forest fragments, which accounts for much of the decline in animal populations in rainforests. Species extinctions occur more rapidly in fragments, for these reasons, and also because species depend upon each other.

(ii) When forests are cut down or burned, the resulting gaps are too large to be filled in by the normal regeneration processes. This permits the ascendancy of rapid-growing, light-tolerant species, and grasses. Large gaps may then be converted to scrub or grassland.

(iii) The use of herbicides and the introduction of exotic species into areas surrounding forest fragments are detrimental to forest health. Herbicides blow from cleared agricultural areas into forests, and exotic species introduced by farmers and ranchers spread, often displacing native species. These exotic organisms interrupt the forest ecosystem and, since they have few or no natural enemies in their new environment, they are difficult to eradicate.

(iv) The fragmentation of forests by logging and agricultural conversion also exaggerates the probability of major epidemics. Pathogens introduced through human activities by land-use practices in areas surrounding the forest can be lethal to forest plants and animals.

(v) Rainforests are losing species, not only because of the disappearance of their habitat but also because essential ecological processes are being interrupted by fragmentation. Fragments are much more easily accessible to human incursions than are intact forests. This leads to a variety of extractive activities within the forest interior.

Intensive hunting, by depleting animal populations, inhibits plant reproduction, since many seeds can neither be dispersed, nor flowers are pollinated without them. Where these seed dispersers have been eliminated, are at low population densities, or cannot move between forest fragments, seed dispersal will be very limited, and as a result tree species dependent upon animal dispersers may become locally extinct.

6. Introduction of exotic species:

Human beings, by introducing exotic species (species belonging to some other place) whether intentionally or accidentally, have created ecological crises in many regions. Sometimes, the exotic species disrupt local ecosystems and, in some cases, even drive the native species to extinction.

7. Overgrazing:

The feeding of the world's livestock is a major problem as fodder is not available in plenty throughout the year, in many areas. The poor people allow their livestock to graze the forests and grasslands, which also causes biodiversity loss.

8. Natural Calamities:

Catastrophic events like floods, droughts, cyclones, volcanoes, fires, etc. cause severe biodiversity loss from time to time.

Endangered and Endemic Species of India:

The population has the potential to extend forward in time, but various factors may prevent the perpetuation of the species. Of the well-known species, there are several which are under threat by human activity. International Union for Conservation of Nature and Natural Resources (IUCN) categorized these species as vulnerable, rare, threatened, and endangered species.

Several plant and animal species in the country are now found in only one or a few protected areas. Among the important endangered animals are charismatic species such as the tiger, the elephant, the rhino, etc. The less well-known major mammals restricted to a single area include the Indian wild ass, the Hangul or Kashmir stag, the Golden langur, the pygmy hog, and a host of others.

There are also endangered bird species such as the Siberian crane, the Great Indian Bustard, the Florican, and several birds of prey. In the recent past, vultures which were common a decade ago, have suddenly disappeared and are now highly threatened. Equally threatened are several species of reptiles and amphibia. Many invertebrates are also threatened, including a large number of species that inhabit our coral reefs.

Many plant species are now increasingly threatened due to changes in their habitats induced by human activity. Apart from major trees, shrubs, and climbers that are extremely habitat-specific and thus endangered, there are thousands of small herbs which are greatly threatened by habitat loss. Several orchids are yet another group of plants that are under threat. Many plants are threatened due to overharvesting as ingredients in medicinal products.

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