What is Biodiversity? Definition, Types And Importance

What is Biodiversity

Biological diversity or biodiversity is the variety of all life forms of all types of ecosystems (terrestrial, aquatic, marine) on the planet. The land, air and seas are home to the tiniest insects, microbes and also the largest animals and plants that all comprise the earth's biodiversity.

Types of Biodiversity

Biodiversity can be classified based upon either hierarchy of life or taking community as a reference.

Classification of biodiversity based upon hierarchy of life:

1. Genetic Diversity

It refers to the variety of genes contained in a particular species or in all living species on the planet. It contains different genetic characteristics of species. Genetic diversity serves as a way for populations to adapt to changing environments. With more genetic variation, it is more likely that some individuals in a population will possess characteristics that are better suited for the environment. The population of a genetically diverse species can continue for more generations because of the success of its individuals.

2. Species Diversity

It refers to the variability of species in a region. It has three components:

Species Richness - It is total number of species in a region

Species Evenness - It is relative abundance (in terms of numbers) of species in a region

Species Dominance - It is the most abundant species in a region.

To understand the differences amongst these, imagine two ecological communities as illustrated in figure below-

In both the communities, species richness is 5 as there are five species represented by a, b, c, d and e. However, species evenness differs for both communities.

In the first community, all the species are equally abundant with five individuals each; whereas in the second community, species 'a' is more abundant (with 13 individuals) as compared to the rest of the species (with three individuals each).

Species diversity entails both richness and evenness. If one casually walks through these ecological communities, Community 1 would appear to be diverse while in Community 2, dominant species 'a' would be seen most of the time. Therefore, species diversity for Community 1 is higher than that of Community 2.

The most abundant species in a community is the dominant species. In the above example of Community 2, species 'a' is dominant. Community 1 does not have any dominant species as all species have an equal number of individuals present.

3. Community or Ecosystem Diversity

It refers to different kinds of biotic communities or ecosystems in a given region. There are many different kinds of

ecosystems like forests, deserts, mountain slopes, ocean floor, etc. Each ecosystem provides many different kinds of habitats with its own biotic community.

Whittaker (1960) suggested the classification of biodiversity based upon community as a reference:

1. Alpha Diversity (within community diversity) refers to diversity of species within the same community or habitat.
2. Beta Diversity (between community diversity) refers to rate of replacement of species between two habitats or communities.
3. Gamma Diversity refers to diversity of habitats over the whole geographical area.

**Students Sometimes Ask** What is Meant by Agro-Biodiversity?

Food and Agriculture Organization (FAO) defines agro-biodiversity (or agricultural biodiversity) as 'the variety of animals, plants and micro-organisms that are used directly or indirectly for food and agriculture. including crops, livestock, forestry and fisheries. It comprises the diversity of genetic resources (varieties, breeds) and species used for food. fodder, fibre, fuel and pharmaceuticals. It also includes the diversity of Non harvested species that support production (soil micro-organisms, predators, pollinators) and those in the wider environment that support agro-ecosystems (agricultural, pastoral, forest and aquatic) as well as the diversity of the agro-ecosystems.'

Abundance of Biodiversity

Our planet supports an amazing diversity of life. This biological diversity has changed through geologic time. Up to now, scientists have identified and named approximately 1.4 million species, but the actual number of species is much more than this. Scientists have disagreements over exact number of species as the biodiversity is not constant. New species evolve and existing ones become extinct over time. Another limitation in knowing the exact number of species is that many parts of the earth, like oceans, are still not explored well by the scientists.

Significance of Biodiversity

Biodiversity holds immense significance for mankind and adds value to human life in following major ways:

1. It forms the basis of ecosystem working and services. All the ecosystem services are provided by biodiversity.

For example:

• All the food resources of the world - crops, fisheries or livestock - are part of biodiversity.
• Many pharmaceutical products are derived from biodiversity, e.g. medicine quinine to fight malaria is obtained from trees.
• Soil biodiversity/biota plays a critical role in soil formation.
• Photosynthesis by trees and plants helps in climate regulation by absorbing carbon dioxide from the atmosphere.
• Pollination carried out by natural pollinators like bats, bees, birds is largely responsible for world's crop production.

2. Biodiversity provides channels for energy transfer and nutrient cycling across the trophic levels in ecosystems.

3. Presence of biodiversity ensures seamless functioning of food chains and food webs and therefore maintains ecosystem stability. Removing any species from its biotic community disrupts the food webs, energy and nutrient flows through the ecosystem. This in turn, compromises the ecosystem functioning and stability.

Understanding the significance of biodiversity helps to better appreciate the need for biodiversity conservation. However, there is also an ethical dimension to biodiversity conservation. Every species over the planet has a 'normal right to exist. 'This is also stated in the UN General Assembly World Charter for Nature, signed in 1982 and this right is independent of its value to the people.

Factors Governing Distribution of Biodiversity

Biodiversity is not uniformly distributed on the earth's surface. Abundance of biodiversity and species richness depends upon environmental factors like climate and availability of essential resources like nutrients. In general, biodiversity varies across latitudes; with greater diversity occurring at lower latitudes. This is because of the warmer temperatures and sufficient rainfall at lower latitudes. Both in terrestrial and marine ecosystems, there exists a latitudinal gradient of species richness, that is, species richness is the maximum at equator and decreases towards the poles.

Variation of Species Richness and Primary Productivity for Terrestrial and Marine Environments

Terrestrial Environments	Marine Environments
1. Species richness decreases from the equator towards the poles	1. Species richness decreases from the equator towards the poles
2. Primary productivity decreases from the equator towards the poles	2. Primary productivity of oceans increases from the equator towards the poles except in localised areas of upwelling. Primary productivity in oceans is influenced by seasonal dynamics of thermocline and upward transport of nutrients from the deep oceans
3. Species richness has a positive correlation with primary productivity	3. Species richness has inverse relationship with primary productivity

Distribution of Biodiversity

Large-scale global pattern of geographic distribution of biodiversity can be studied through the following concepts:

1. Biomes

• The concept of biomes was given by ecologists F.E. Clements and V.E. Shelford in 1939. They defined the biome concept as a classification of world's predominant vegetation patterns (like forests, grasslands, shrublands, deserts). However, they combined broad-scale distribution of both plants and animals while classifying major biomes of the world.
• Thus, a biome can be defined as a large geographical region with its predominant community of plants and animals.

2. Biotic Provinces or Biogeographic Realms

• The concept was given by British biologist Alfred Russell Wallace in 1876.
• A biogeographic realm or biotic province is a region inhabited by distinctive kind of animal life (so the basis of classification is fundamental features of animals found in a region).
• Every such biotic province is bound by barriers that limit the spread of life to other regions and immigration of foreign species to it.
• These regions are also called as Wallace Realms and there are six main biotic provinces.

Major Biomes of the World

There are nine major biomes across the world described hereunder:

1. Tropical Rainforests

These are found between 10 degree north and 10 degree south of the equator. Major regions of the tropical rainforests of the world are Amazon and Orinoco basin of South America, South Central America, Gulf of Guinea region, Congo basin of Africa, South east Asia comprising Indonesia and Malaysia and South Pacific Islands like Papua New Guinea.

These regions have warm temperatures throughout the year with mean monthly temperatures of usually more than 20°C. Annual rainfall is 200 to 225 cm and is well distributed throughout the year with almost daily rainfall. There is no distinct season in these regions and the annual range of temperature is very small (usually less than 5°C)

The tropical rainforests are the most biologically diverse and productive terrestrial ecosystems of the earth. These cover only about 6% of the land surface but account for more than 50% of all the plant and animal species. The trees are evergreen, broad-leaved and have hardwood.

The forests have a vertical stratification of vegetation with five major layers - (i) emergent trees with height 50-60 meters, (ii) upper canopy with trees 25-35 meters tall, (iii) lower canopy with tree height as 15-24 meters, (iv) poorly developed shrubs and (v) ground layer of herbs and ferns. Vegetation also comprises lianas (climbing vines), epiphytes and strangler figs. The trees have buttressed roots that support them in shallow soils. Examples of such tree species are mahogany, ebony, dyewood, greenheart and cabinet wood.

The tropical rainforests also have incredibly rich number of faunal species. Many animal life forms like arboreal mammals and primates including gibbons, langurs and macaques are common here. There is also abundance of chameleons, snakes, frogs, birds, ants, etc.

2. Tropical Deciduous Forests or Tropical Monsoon Forests

These occur between latitudes 10-30 degrees north and south of the equator on the eastern margins of the continents which are under the influence of trade winds. Particular regions include eastern Brazil, parts of Central America, eastern Africa, Indian sub-continent, parts of

South east Asia like Myanmar, Thailand, Laos, Cambodia, Vietnam, northern and north eastern Australia.

These regions have a characteristic tropical monsoonal type of climate due to the differential heating of land and water. The climatic conditions are marked by the seasonal reversal of the trade winds and seasonal migration of Inter Tropical Convergence Zone (ITCZ).

The winds become on-shore in summers and off-shore in winters, thus there is a distinct dry season in these regions. The length of the dry season varies based upon the distance of the region from the equator. As the distance from the equator increases, length of dry season also increases.

The natural vegetation of tropical monsoonal forests comprises tropical deciduous trees and shrubs that drop their leaves during the dry season. New leaves grow at the onset of the rainy season. These forests have their species richness next only to that of tropical rainforests. Some common tree species are teak, sal, bamboo, mahua, babul and jamun.

3. Tropical Grasslands or Tropical Savannas

The tropical grasslands of the world are the tropical and subtropical regions receiving annual average rainfall of 25-150 cm. These occur in the central and eastern Africa, southern Africa (north of Tropic of Capricorn), Brazilian highlands, parts of Orinoco basin of South America and semi-arid regions of India and northern Australia.

Being tropics and sub-tropics, these regions have warmer continental climates with mean monthly temperatures not below 20°C. Tropical savannas have a distinct seasonality in precipitation with one or two prolonged dry periods. Wet season coincides with summers and dry season with winters. The seasons are primarily regulated by moisture and not by temperature. The annual precipitation received here is less than that over tropical forest biome.

As in the case of tropical climates, the amount of precipitation decreases as the distance from the equator increases.

Tropical grasslands are mixed grasslands with scattered trees or clumps of trees. This biome has an array of vegetation ranging from open grasslands to widely spaced shrubs or trees (woody vegetation) along with grasses. Thus, the characteristic feature is codominance of grasses and woody vegetation. Availability of moisture controls the density of woody vegetation. But grass cover is always present. In South America, tropical grasslands with lower tree density are called as Campos (in Brazilian highlands) and Llanos (in Orinoco basin); whereas, tropical grasslands with higher density of trees in South America are called Cerrados. Fire is a very important part of the savannas biome. Thus, the dominant vegetation is always fire adapted here. A few important tree species of savannas biome are acacia, palm and baobab in Africa and acacia and eucalyptus in Australia. Tropical grasslands support animals like large herbivores (zebras, antelopes, giraffes) as well as carnivores (lions, cheetah, leopard, hyenas). Savannas also host a large variety of insects like grasshoppers, flies, locusts, ants, dung beetles, etc.

4. Tropical Deserts

These are the tropical regions of the world with annual rainfall generally less than 25 cm. The latitudinal range of tropical deserts extends from about 20-30°C north and south of the equator.

The Sahara desert of North Africa is the largest stretch of hot tropical desert. It extends towards its east as the desert of the Arabian Peninsula, further eastward to Iran, Pakistan and finally as Thar desert of India. In the southwestern North America (i.e. regions of Arizona and California in the USA and Mexico) tropical deserts are called by different names like Californian, Sonoran, Mojave and Mexican. Tropical deserts in southern hemisphere include Atacama desert along the coastal regions of Chile and Argentina in South America, Namib and Kalahari desert of southern Africa and the Great Australian desert.

These regions coincide with the sub-tropical high pressure belt areas where the air that is carried aloft along the ITCZ starts to sink. As the air descends, it warms up and thus there are cloudless skies. Temperatures can be as high as 40-45°C during summers. The cold ocean currents along the western coasts of the continents also aggravate the already arid conditions along the coasts.

Due to the low rainfall and high rates of evaporation in these regions, the soil moisture is insufficient to support high primary productivity. The plants and animals of deserts are well adapted to water scarcity conditions in these regions. Some of the adaptations of the plants in deserts include:

• Drought-evading plants which avoid droughts by growing only when rain happens
• Deep roots also called taproots go deep into soils till ground water tables
• No leaves or few leaves or needle like leaves
• Succulent stems such as those of cacti which can store moisture

These biomes support a wide variety of animals like mammals, birds, snakes, lizards, beetles, ants, etc.

Apart from the tropical deserts, there are also mid-latitude or temperate deserts. Examples include KaraKum desert region in Central Asia, deserts like Takla Makan and Gobi Desert of in Eastern Asia. These regions have arid conditions due to the continentality effect as these are far off from water bodies. These regions have warm summers and long cold winters. Patagonian desert of South America is also a temperate desert due to the rain shadow effect of Andes.

5. Mediterranean Biome or Sclerophyllous Shrublands

This biome corresponds to the Mediterranean type of climate that exists in latitudinal range of 30-45 degrees north and south of the equator along the western margins of the continents.

The largest stretch of the Mediterranean biome is in the areas bordering Mediterranean Sea, that is, southern Europe and northern Africa. Other locations of Mediterranean biome are central Chile, the Cape region of South Africa, western California in North America, south western and southern Australia.

The characteristic climatic feature of this biome is the winter rainfall due to the influence of on-shore westerly winds. Winters are cool with average temperatures around 10-12°C.

During summers, these regions come under the influence of off-shore trade winds. Thus, summers are hot and dry.

The vegetation comprises of evergreen shrubs and dwarf trees. Such type of vegetation is called as sclerophyll vegetation, Main features of this vegetation are small hard leaves, thick cuticles and sunken stomata that reduce transpiration losses during hot summers. Sweet smelling bushes like lavender, rosemary, laurel, myrtle commonly grow here. Evergreen trees like oaks and eucalyptus (in Australia) are also found. The regions are prone to fire during summer season. It helps to continue the dominance of shrubs at the expense of trees. The shrubs grow vigorously after the fire and following the first rain. The animal kingdom also comprises of variety of birds, reptiles, rodents etc.

These shrublands are known by various names - Fynbos in Cape Province of South Africa, Mallee in Australia, Chapparal in North America, Matorral in Chile and Maquis of France.

6. Temperate Grasslands

These are found in the mid-latitude regions in latitudinal range of about 40-55 degrees north and south of the equator in the continent interiors. These grasslands are known by different names in different parts of the world. These are called Steppes in Eurasia (Russia and Ukraine), Pustaz in Hungary prairies in North America, Pampas in Argentina and Uruguay, High Veld of southern Africa and Downs in Murray-Darling basin of Australia.

Being in the continent interiors, the annual precipitation of these regions is 25-75 cm, which is intermediate between deserts and forests. Summers are warm in these regions with average temperatures of 18-24°C; winters are cold. The steppes are the drier type of grasslands due to the vast continental extent of Eurasia. In contrast, prairies are wetter than the steppes.

The height of the grasses depends upon the amount of precipitation received. They can be tall-grass, mid-size grass and short-grass types. Some types of grasses may have adaptations to grow in summers, whereas a few others may grow in winters. Grasses have deep roots-up to two meters deep into the soil. Common species are alfalfa and lucerne. The natural grasslands have been converted to extensive mechanised agricultural fields of wheat and corn or cultivated pasture lands. Large herbivores like bison, kangaroos are common in the natural grassland regions.

7. Temperate Deciduous Forests

Temperate deciduous forests dominate the wetter temperate regions in the latitudinal range of 45-60 degrees north and south of the equator on western margins of the continent. This biome occurs in parts of Europe - Britain, northern and western France, Belgium, Netherlands, Denmark and western Norway; coastlands of British Columbia in North America; southern Chile in South America; Tasmania and most parts of New Zealand.

These regions have warm summers with average temperatures around 18-24°C. Winter temperatures are sub-zero with snowy and frosty conditions. However, the winters are milder for their latitudes due to the moderating influence of the neighbouring seas. The prevailing winds are westerlies.

Thus, these regions receive their annual precipitation from on-shore westerlies and also from the temperate cyclonic activity. Annual precipitation is 75-150 cm, which is evenly distributed throughout the year.

The broadleaf hardwood trees of the temperate deciduous forests shed their leaves in the autumn season before the onset of winters. The leaves regenerate in the spring when temperature and day length increase. Important tree species are elm, oak, maple, beech, birch, chestnut, hickory etc. Apart from trees, temperate deciduous forests have another layer of vegetation comprising of herbs and shrubs. Animal species include deer, bear, foxes, turkey and squirrels.

8. Coniferous Forests or Taiga Forests or Boreal Forests

The coniferous forests are found in the circumpolar belt across the Northern Hemisphere in latitudinal range of 55-70 degrees north of the equator. The geographical distribution extends across North America (southern Alaska and most of Canada), Europe (parts of Norway, Sweden, Finland, northern Russia and northern Siberia) and terminating into Asia.

The summers in these regions are short and cool with maximum temperature of 20°C. The winters are long and bitterly cold with temperatures as low as -40 to -50°C at some locations. Some locations of this biome (like central Siberia) experience the largest annual range of temperature of as much as 100°C. Annual precipitation is around 25-100 cm.

These regions are the largest natural vegetation formation on earth. The forests have only a few species (mainly coniferous type) which are well adapted to withstand the winter climatic extremes of this region. The trees are cone shaped, have drooping down stems and needle like leaves. Common species include pine, fir, spruce, cedar and larch (deciduous type). These are softwood type trees commercially exploited for paper and pulp industry. These forests have a unique animal community comprising of herbivores like caribou, elk (the largest deer), arboreal red squirrel and predators like wolf, lynx, owl etc.

9. Tundra Biome

This is treeless land between the coniferous forests to the south and polar ice caps to the north. Its name comes from a Finnish word- tunturi -meaning a treeless plain. It is the most fragile biome with very low species diversity. Tundra regions are characterised by permafrost or permanently frozen sub soil layer. In permafrost, the top soil thaws during summers and then freezes again in winters.

These regions have long winters extending for 9-10 months, without the daylight. The winter temperatures may be as low as -30 to -40°C. Summers are short with continuous daylight and temperature of up to 10°C. Annual precipitation is less than that in the regions supporting coniferous forests. However, the greatest limiting factor for plants to grow is the availability of sunlight.

The natural vegetation comprises plants like mosses, lichens, sedges, dwarf woody plants and rhododendrons. The animal life comprises large number of migratory birds and insects. Large animals like wolf. musk ox, caribou, reindeer, polar bear and fox are also found here.

Right at the poles and at the peaks of the high mountains, there will be ice caps. Green ice algae and a variety of heterotrophic microorganisms may live in and under the ice.

At the lower latitudes, alpine tundra is found at the higher elevations of the mountains. These regions have harsh environments like snowy precipitation and steep slopes. Natural vegetation may comprise rhododendrons and shrubby thickets.

Some Biodiversity Rich Regions of the World - Biodiversity Hotspots & Megadiverse Countries

As already discussed, biodiversity is not uniformly distributed across the world. It is important to study the biodiversity rich regions as they hold special significance for conservation.

1. Biodiversity Hotspots

The concept of biodiversity hotspot was first given by Norman Myers in 1988. Later, in 1989, Conservation International (CI) adopted Myers' concept and defined it further. A region is classified as a Biodiversity Hotspot if it meets undermentioned two criteria:

• It must have at least 1,500 vascular plants (>0.5% of world's total) as endemics
• It must have 30% or less of its original natural vegetation, or it must be threatened.

There are 36 biodiversity hotspots across the world. These represent just 24% of the earth's land surface but support nearly 43% endemic species of birds, mammals, reptiles and amphibians.

2. Biodiversity Hotspots in India

india has four of biodiversity hotspots of the world.

These include:

• Himalayas: It includes the entire Indian Himalayan Region.
• Indo - Burma: It includes entire north-east India (except Assam) and Andaman group of islands.
• Sundaland: includes Nicobar group of Islands.
• Western Ghats.

3. Megadiverse Countries

This concept was given by Conservation International in 1998. It refers to world's top biodiversity rich countries. To qualify, as a megadiverse country a country must:

• Have at least 5,000 of world's plants as endemics.
• Have marine ecosystems within its borders.

Apart from these two, some other criteria like species and ecosystem diversity are also taken into consideration.

There are 17 megadiverse countries which account for at least two-thirds of all non-fish vertebrate species and three-fourths of all higher plant species. This classification demonstrates how a small number of countries hold large proportion of global diversity and therefore have greater responsibility for conservation and biodiversity management. India is one of the mega-diverse countries of the world.

Biological Diversity and Genetic Engineering

Genetic Engineering is defined as the process of altering the genetic material (DNA) of organisms (plants, animals and micro-organisms) in a way that does not occur naturally by mating and/or natural recombination. It is done by using biotechnology in laboratory.

Through the selective manipulation of DNA, specific genetic characteristics can be transferred from one individual to another or from one species to another. Such organisms are called as Genetically Modified Organisms (GMOs).

Scientists have conducted laboratory experiments for genetic engineering of both plants and animals. However, there are very strong ethical concerns about genetic engineering of animals. The genetically engineered crops are more common and have been widely used since the mid 1990s in several countries. GM crops are produced with specific traits like insect-resistance, weed-resistance, drought-tolerance and virus-resistance. A few examples

of GM crops are canola, maize, cotton and soybean. The use of GM crops has given rise to environmental debates along with the promise of increased agricultural production.

Some of the major environmental concerns associated with the use of GM crops are:

1. GM crops can start cross-pollination with the non-GM crops and wild species. This results in genetic contamination of the native genetic diversity. It is very difficult to contain or reverse this impact Maintaining indigenous genetic diversity is critical for agriculture.
2. Some scientists suggest 'superweeds' can be created by transfer of some new hybrid characteristics by interbreeding with weeds. Also, the use of GM crops can result in weeds and pests becoming resistant over a period of time. Such 'superweeds' or 'superpests' can start attacking the GM variant crop. For example, due to constant exposure to a single herbicide in case of HT crop, many (more than 20) species of weeds in the U.S. are now resistant to Monsanto's glyphosate-based herbicide. One way to contain the above adverse ecological impact is through the technology of 'terminator gene' which makes the seeds from a crop sterile. It prevents the GM crop from spreading further on field on its own. However, this poses economic concerns for the farmers in developing countries like India. They may not be able to afford the purchase of new seeds before every sowing.
3. Through genetic modification, crops can be made pest/insect resistant. An example of this is Bt (Bacillus thuringiensis) Cotton. Bacillus thuringiensis bacteria is a natural pesticide. The gene that makes the pesticide (Bt) is paced in cotton plant through genetic engineering. This reduces the use of pesticides which has a positive effect on the environment in general. But at the same time HT (herbicide tolerant) GM crops are criticised for increasing chemical herbicide use in agriculture.
4. GM crops can also have some unintended environmental impacts on the non-target species. One such case came to light from the USA. For example, like Bt Cotton, Bt Corn contains its own pesticide in every cell of the plant. It was found that the pollen from the Bt corn was toxic for the monarch butterflies. The butterflies died by consuming the food containing Bt corn pollen.

The jury is still out on what will be the long-term ecological impacts of GM crops or whether benefits will outweigh the undesirable effects. GM crops in Indian context will be discussed in Chapter 16 of the book.

Some Key Terms

1. Endemic Species

Those species which are restricted to only one geographic region and not found anywhere else.

For example, lion tailed macaque is a primate species endemic to Western Ghats of India. Nilgiri tahr is a wild sheep species endemic to Western Ghats. Red sandal wood (or Red Sanders) is endemic to southern parts of Eastern Ghats.

2. Keystone Species

The term was first used by Robert Paine (1966). These are those species which have a significant effect on the ecological community even in their relative small numbers. Without the keystone species, the ecosystem would be dramatically different or cease to exist. Any plant, fungi, herbivore or carnivore can be a keystone species.

For example, elephants are a keystone species for African savannas. Elephants feed upon small trees and shrubs which keep savanna as a grassland and not get converted to a forest.

3. Umbrella Species

These species have a very large habitat needs upon which many other species depend. Umbrella species are different from keystone species. An umbrella species is determined based upon its large habitat needs whereas a keystone species is determined based upon its role for maintaining the ecosystem structure.

For example, Siberian tiger is an umbrella species with its territory stretching across Russia, China and North Korea.

4. Foundation Species

These play a critical role in the creation of a habitat in an ecosystem.

For example, coral polyps are foundation species for coral reef ecosystems as their rocky calcareous exoskeletons create enormous habitats where many other marine organisms like microscopic plankton, Mollusca, fishes, marine reptiles, etc., thrive.

5. Indicator Species or Sentinel Species

These are extremely sensitive to any kind of environmental change in an ecosystem. Therefore, these are like biological smoke alarms which give early warnings of deteriorating conditions in a habitat.

For example, coral polyps are extremely sensitive to changing climate and other environmental conditions. Adverse climatic conditions lead to coral bleaching.

Another example is of Gangetic dolphin. This freshwater fish is a reliable indicator of health of entire river ecosystem. Lichen (in which algae and fungi live in a symbiotic relationship with one another) is extremely sensitive to air pollution, especially sulphur dioxide and gets killed by it.

6. Flagship Species

These species act as a symbol for a habitat, environmental issue or campaign. Therefore, these can be mascots for entire ecosystem.

For example, the Great Indian Bustard is a flagship grassland species in India. Tiger is a flagship species in India and is a symbol of wildlife conservation. Polar beers are flagship species of climate change challenges for biodiversity.

Same species may fall into multiple categories. For example, tiger is a keystone species and also a flagship species. Similarly, coral polyps are both foundation and indicator species