What is Biodiversity? Why Is It Important? Definition, Types, Importance, Measurement

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What is Biodiversity

Biodiversity found on Earth today consists of many millions of distinct biological species, the product of four billion years of evolution.
Biodiversity is the variety of life on Earth, it includes all organisms, species, and populations; the genetic variation among these; and their complex assemblages of communities and ecosystems. It also refers to the interrelatedness of genes, species, and ecosystems and in turn, their interactions with the environment.

Definition of Biodiversity

Biodiversity is defined as ‘the variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems’.
Conservation and sustainable use of biodiversity is fundamental to ecologically sustainable development. Biodiversity is part of our daily lives and livelihood, and constitutes resources upon which families, communities, nations and future generations depend.
Biodiversity refers to the variety and variability of organisms, of genetic material and of community or ecosystem. This includes diversity within species (genetic diversity), between species (organismal diversity) and ecosystem or community (ecological diversity). Biodiversity refers to the variety and variability among living organisms and the ecological complexes in which they occur.
Biodiversity encompasses all the levels of natural variations from the molecular and genetic to the species level, where we have most of our interaction with biodiversity through enjoyment of the common, strange and beautiful form of life or through suffering caused by the effects of pests, parasites and diseases.
For the assessment of global biodiversity, it is defined as the total diversity and variability of living organisms and of the systems of which they are a part. This covers the total range of variation and variability among systems and organisms at the bioregional, landscape, ecosystem, habitat (levels), and organismal level down to species, populations, individuals and genes (genetic diversity).
The variety of organisms considered at all levels of genetic variants belonging to the same species through, arrays of species, genera, families and still higher taxonomic levels including the variety of ecosystems which comprise both communities of organisms within a particular habitat and the physical condition under which they live.
The simplest approach to define biodiversity is, the ensemble and the interacts of the genetic, species and the ecological diversity in a given place and time.
Different people perceive biodiversity differently. For example, scientists aiming to conserve biodiversity in an ecosystem may give prime importance to the processes that support the maximum variety of organisms. While a lawyer gives priority to legal aspects of conservation criteria ignoring variation between organisms. Similarly, perception will differ between those who live in a developed, developing and under-developed countries and even in the cities and rural areas. Attitude towards biodiversity also varies among the affluent classes, ecosystem people and the ecological refugees. However, the primary aim of biodiversity study is that it provides clue for conservation.
The present day diversity pattern of organisms emerged because of speciation (diversification) and extinction. To understand this, it requires to investigate the underlying genetic processes, estimate the relative past and present rates of speciation or extinction and understand how these rates are being altered by demographic pressures.
Apparently, it appears that measurement of biodiversity may be based on any unit of the three (genetic, organismal and ecosystem diversity) levels, but it is difficult to choose a single unit from each of these three groups as a fundamental or natural unit for measurement. However, 'interaction is the main intrinsic mechanism that shapes the characteristics and the functioning of biodiversity.
Genes are the fundamental unit of the living world, but hardly serve as the general purpose of rapid recognition and assessment of biodiversity. For convenience and practical purposes, obviously species serve as the most measurable unit that occur discretely in nature. As such, species diversity is synonymous with organismal diversity vis-à-vis, biodiversity. Turning to ecosystem diversity, no measurable unit can be fixed for assessment, since it refers to the variety of ecological roles played by different species in a community or in a habitat.
Another component of biodiversity is the cultural diversity, which is referred to the diverse cultures developed by different groups of people during their long association with nature. The diverse cultures with different religious ideas, indigenous knowledge, myths, taboos, conservation ethics, sustainable use of resources with respect to biodiversity, vary greatly within and between the communities. Thus, man has largely evolved with the diverse organisms around him. Hence, biodiversity forms an essential element of culture that helps in civilization to flourish. Australopithecines first initiated tool making which they used for hunting. This marked the emergence of cultural revolution (extra-somatic inheritance) in man. Different cultural practices have been playing a pivotal role in which biodiversity is maintained, preserved and appreciated by the indigenous people. Maintaining diversity of domestic plants and animals is also a part of this cultural practice.

History of Biodiversity

The term 'diversity' is not new, rather has a long history, but 'biological diversity' came into use in scientific literature only in the 1980s. The term was first coined by Elliot Norse (1980) in a US government report.
Norse and McManus (1980) tagged to it 'genetic diversity' and 'ecological diversity' Subsequently, several other authors, equated ecological diversity with species richness which meant the total number of species in a community. However, in 1986, Norse et al. elaborated the concept to refer to biological diversity at three levels: genetic (within species), species (species numbers) and ecological (community diversity).
The concept of 'biodiversity' was popularized in the first planning conference of the 'National Forum on Biodiversity, Washington D.C., on September 1986. Wilson and Peter (1988) edited the proceedings of the conference titled Biodiversity. Subsequently, the term 'Biodiversity' was first published in the Biological Abstracts, BIOSIS database in 1988, containing only four references and by the end of April, 1994 that accounted up to about 888. Since then numerous scientific papers, books and periodicals were published that expanded the concept. Edward Wilson actually elaborated the concept in his book The Diversity of Life (1992).
Convention on Biological Diversity in June 1992, constituted a historical commitment by all nations of the world (although all nations have not yet ratified or signed). For the first time, biodiversity was comprehensively addressed in this binding global treaty. At the same time the genetic diversity was considered and conservation of biodiversity was accepted as the common concern for the cause of human welfare.
According to the Article 1 of the convention: "The provisions are the conservation of biological diversity, the sustainable use of its components and the fair and equitable sharing of benefits arising out of the utilization of genetic resources, by appropriate access to genetic resources and by appropriate transfer of relevant technologies, taking into account all rights over those resources and to technologies, and by appropriate funding".

Types of Biodiversity

Biodiversity is considered to exist at three levels: genetics, species, and ecosystems.
  • (a) Genetic diversity
  • (b) Species diversity
  • (c) Ecosystem/ Community diversity

(a) Genetic diversity
  • It is concerned with the variation in genes within a particular species. 
  • Genetic diversity allows species to adapt to changing environments. 
  • This diversity aims to ensure that some species survive drastic changes and thus carry on desirable genes. 
  • The survival of individuals ensures the survival of the population. 
  • The genetic diversity gives us beautiful butterflies, roses, parakeets or coral in a myriad hues, shapes and sizes.

(b) Species diversity
  • It refers to the variety of living organisms on earth. 
  • Species differ from one another, markedly in their genetic makeup, do not inter-breed in nature. 
  • Closely-related species however have in common much of their hereditary characteristics. For instance, about 98.4 percent of the genes of humans and chimpanzees are the same.
  • It is the ratio of one species population over total number of organisms across all species in the given biome. 
  • ‘Zero’ would be infinite diversity, and ‘one’ represents only one species present.
(c) Ecosystem/ Community diversity
  • This refers to the different types of habitats. A habitat is the cumulative factor of the climate, vegetation and geography of a region. 
  • There are several kinds of habitats around the world. Corals, grasslands, wetland, desert, mangrove and tropical rain forests are examples of ecosystems.
  • Change in climatic conditions is accompanied by a change in vegetation as well. Each species adapts itself to a particular kind of environment. 
  • As the environment changes, species best adapted to that environment becomes predominant. Thus the variety or diversity of species in the ecosystem is influenced by the nature of the ecosystem.

Measurement of Biodiversity

Biodiversity is measured by two major components: 
  • i. species richness, and 
  • ii. species evenness.

(i) Species richness
It is the measure of number of species found in a community

a) Alpha diversity
It refers to the diversity within a particular area or ecosystem, and is usually expressed by the number of species (i.e., species richness) in that ecosystem.

b) Beta diversity
It is a comparison of diversity between ecosystems, usually measured as the change in amount of species between the ecosystems

c) Gamma diversity
It is a measure of the overall diversity for the different ecosystems within a region.
(ii) Species evenness
It measures the proportion of species at a given site, e.g. low evenness indicates that a few species dominate the site.

Importance Of Biodiversity

Life appeared on earth, more than 3.5 billion years ago. Since then the world has faced five episodes of mass extinction which occurred by natural calamities. However, the sixth one is predicted to be framed by man.
Relatively human beings are newcomers in the world, but they have maximally destroyed and manipulated the living world around them. They have invaded, established and conquered the territories of other animals.
Earth is on a continual process of changing naturally, with man enhancing this process manifold. Habitats are altered and modified that have maximally affected their inhabitants. Both renewable and non-renewable resources have been overexploited. Natural ecosystems are thus subjected to multiple use, leading to conflicting demands for bioresources by various interested groups and user agencies. Current rates of species extinction have thus multiplied and exceeded thousand times more than the normal. Exponential rise in population compounded with poverty in the third world countries, the destruction of major habitat types and global climatic shifts, threaten all the evolutionary and ecological processes. Political, social and economic factors have fuelled the loss further. Moreover, science and technology explore new ways to exploit biodiversity every day, which negatively influences species diversity.
A species once lost is lost forever, as relation between various species, in a community breaks down. For example, extermination of pollinating animals can doom the plants they pollinate. Almost 15589 species are already extinct while the total number of threatened species has increased from 5205 in 1995 to 7266 in 2004.
Biodiversity plays a vital role in the material well being of man as well. Widespread loss of biodiversity has put man's existence at stake. The diverse organisms interact with the environment over billions of years and provide an atmosphere to breathe, soil to grow crops and fresh water to drink. So conservation should aim at the totality of life, preserving each and every element of nature. Besides, there are moral and aesthetic grounds for conservation of each individual species. Blanket preservation of millions of species might safeguard few. The science of biodiversity as conceived has provided deep insight into the strategy of biological conservation. Conservation of totality of life is thus the primary focus for biodiversity study.
The term biodiversity integrates molecular biology, genetics, taxonomy and ecology. Unfortunately, various disciplines of life science have received less attention compared to others. For example, in many countries, taxonomy is most neglected with low career options while molecular biology is the highly rated one. Likewise, ecology is also been neglected.
Biodiversity is the backbone of agriculture, aquaculture, animal husbandry and forestry and it is linked with social, religious and cultural practices of a region. Therefore, deep understanding of biodiversity is needed for regional development and restoring degraded landscape.
The immense biodiversity of the earth works in a concerted manner to support all the life sustaining functions. The diverse biotic communities maintain ecosystem services and goods that sustain the life supporting system of man. The organisms around us provide us with the large share of our food, industrial raw materials livelihood and even contribute to the growth of our culture and religion. The living resources are the essential components for man's survival and with time the demand on such resources is growing fast.
Economic development of a country is largely dependent on the availability of bioresources. With escalating human population and developmental activities, these resources are depleting at a steady state. Today after a century of industrial development and steady progress of technology, vast tracks of rainforests, wetlands, water bodies, coral reefs and coastal regions have degraded and this is responsible for the irreplaceable loss of global biodiversity. About 30-40 per cent of the tropical rainforest disappeared between 1950 and 1990. The equal amount of forest may be lost in next 30-50 years, and that would culminate into unprecedented loss of biodiversity.
It has been estimated that 12 per cent of birds, 23 per cent of mammals are already critically threatened, many are extinct while thousands are at risk.
Driven by greed and need, man has invaded, established and conquered the territories of other animals. He has deprived other organisms from their legal share of space and food. It has been observed that maximum species extinctions have occurred between 1000-2000 AD, due to undue anthropogenic activities.
The United Nations Millennium Ecosystem Assessment Report (2005), warned that if current patterns of biodiversity loss continue to increase, then the future of human being would be at greatest risk. The current rate of species extinction has exceeded thousand times more than the normal that threatens the evolutionary and ecological processes.
The new era of 'post industrial period' has witnessed the diversification of global competitive products through modern high technology. For this, man's endeavour is to explore the great potential of the biological resources. Biodiversity offers opportunity to invest new element for human development.
Man being part of the natural system shares habitat with other living organisms and each organism has its intrinsic value and the right to exist. Human beings largely ignore the ecosystem services provided by the nature and assign a higher value to products from which they derive economic benefits.
To derive more benefits beyond need, man has destroyed the natural systems with the extinctions of many species. Although, ecosystems are resilient to changes, but can tolerate only a limited range of disturbances. Therefore, extermination of species is actually the prelude to mans' own destruction.
The 'United Nations General Assembly' declared '2010' as the 'International Year of Biodiversity' (Resolution 61/203). The aim was to increase public awareness and make people understand the importance of biodiversity, raise awareness among the accomplished groups and encourage government to formulate rules and policies to reduce threats to diversity. Finally involving stakeholders to formulate action plans post 2010 period is also a part of the programme.
In 2002, Heads of the State and Government at the 'World Summit for Sustainable Development' in Johannes berg, and the signatories of 'Convention of Biological Diversity' at the Earth Summit in Rio de Janeiro, targeted to reduce biodiversity loss by 2010.
The countries participating in the 'Convention on Biological Diversity' (2002), committed to act and achieve a significant reduction of the current rate of biodiversity loss at the global, regional and national levels by 2010.
Further, 'Committee on Biological Diversity, Heads of State of the EU at the European Council in Gothenburg, framed the 'Countdown 2010 alliance, that aims to stop loss of biodiversity before 2010.
In reality, it is impossible to conserve all species and ecosystem. Therefore, each species or area is to be protected, based on their relative importance. However, laws for conservation are enacted, policies are framed, but the agony of the wild continues. Most of the human being are apathetic towards other animals; they kill, hunt and overexploit them; but seldom love them. Wild animals are scared of human being and attack them accidentally, but the human encroach upon the wild animals' territory and make their life miserable. In India, the Protected Area covers only 5 per cent of the total land mass. So the diverse organisms outside the designated areas remain largely unprotected. The year of biodiversity, '2010, demands the cooperation of man to protect nature's variety.

Biodiversity and Food Web

The building blocks of plants, animals and humans are identical, and are made of the four elements - carbon, oxygen, nitrogen and hydrogen. 
These elements are present in the environment - in air, water and soil. However, only green plants can absorb nitrogen from the soil through their roots, and use sunlight and water to produce energy by a process called photosynthesis. They are known as producers. 
Animals and humans, who have plants or other animals as their food, are known as consumers. The chain that links consumers to producers is called the food chain or web. 
Every living creature is found in a food chain. There are several food chains and they can be complex or simple depending on the environment. 
To cite some examples, grasshoppers eat grass and are in turn eaten by frogs; snakes eat frogs and rodents.
Thus the importance of each and every creature in the web 
of life is evident. Tampering with the food chain only pro�duces negative results, leading to the destruction of the species. 
Every time a species becomes extinct, the chain is broken and many species, including humans, move closer to extinction.

Services provided by Biodiversity

Biodiversity provides a number of natural services for human beings:

(a) Ecosystem services
  • Protection of water resources
  • Soils formation and protection
  • Nutrient storage and recycling
  • Pollution breakdown and absorption
  • Contribution to climate stability
  • Maintenance of ecosystems
  • Recovery from unpredictable events

(b) Biological services
  • Food
  • Medicinal resources and pharmaceutical drugs
  • Wood products
  • Ornamental plants
  • Breeding stocks
  • Diversity in genes, species and ecosystems

(c) Social services
  • Research, education and monitoring
  • Recreation and tourism
  • Cultural values

Causes for Biodiversity Loss

Loss of biodiversity occurs when either a particular species is destroyed or the habitat essential for its survival is damaged. The latter is more common as habitat destruction is inevitable fallout of development. 
The extinction of species takes place when they are exploited for economic gain or hunted as sport or for food. Extinction of species may also occur due to environmental reasons like ecological substitutions, biological factors and pathological causes which can be caused either by nature or man.

(a) Natural causes
  • floods, 
  • earthquakes, 
  • landslides, 
  • rivalry among species, 
  • lack of pollination and diseases.

(b) Man-Made causes
  • Habitat destruction
  • Uncontrolled commercial exploitation
  • Hunting & poaching
  • Conversion of rich bio-diversity site for human settlement and industrial development
  • Extension of agriculture
  • Pollution
  • Filling up of wetlands
  • Destruction of coastal areas

Biodiversity conservation

Conservation of biological diversity leads to conservation of essential ecological diversity and preserve the continuity of food chains.

Modes of Conservation

(a) Ex-situ conservation: Conserving biodiversity outside the areas where they naturally occur is known as ex-situ conservation. 
  • Here, animals are reared or plants are cultivated like zoological parks or botanical gardens. Reintroduction of an animal or plant into the habitat from where it has become extinct is another form of ex situ conservation. 
  • For example, the Gangetic gharial has been reintroduced in the rivers of Uttar Pradesh, Madhya Pradesh and Rajasthan where it had become extinct. 
  • Seed banks, botanical, horticultural and recreational gardens are important centres for ex-situ conservation.

(b) In-situ conservation: Conserving the animals and plants in their natural habitats is known as in-situ conservation. The established natural habitats are: 
  • National parks 
  • Sanctuaries 
  • Biosphere reserves and
  • Reserved forests
  • Protected forests

Constraints in biodiversity conservation
  • Low priority for conservation of living natural resources.
  • Exploitation of living natural resources for monetary gain.
  • Values and knowledge about the species and ecosystem are inadequate.
  • Unplanned urbanization and uncontrolled industrialization.

Botanical garden
Botanical garden refers to the scientifically planned collection of living trees, shrubs, herbs, climbers and other plants from various parts of the world.

Purpose of botanical gardens
  • To study the taxonomy as well as growth of plants.
  • To study the introduction and acclimatization process of exotic plants.
  • It acts as a germplasm collection.
  • It helps development of new hybrids.
  • It augments conserving rare and threatened species.

Zoo is an establishment, whether stationary or mobile, where captive animals are kept for exhibition to the public and includes a circus and rescue centers but does not include an establishment of a licensed dealer in captive animals - CZA .
The initial purpose of zoos was entertainment, over the decades, zoos have got transformed into centres for wildlife conservation and environmental education.
Apart from saving individual animals, zoos have a role to play in species conservation too (through captive breeding).

Species judged as threatened are listed by various agencies as well as by some private organizations. The most cited of these lists is the Red Data Book. 
It is a loose-leaf volume of information on the status of many kinds of species. This volume is continually updated and is issued by the International Union for Conservation of Nature (IUCN) located in Morges, Switzerland. 
“Red” of course is symbolic of danger that the species both plants and animals presently experience throughout the globe. 
The Red Data Book was first issued in 1966 by the IUCN’s Special Survival Commission as a guide for formulation, preservation and management of species listed. 
In this Book, information for endangered mammals and birds are more extensive than for other groups of animals and plants, coverage is also given to less prominent organ�isms facing extinction. 
The pink pages in this publication include the critically endangered species. As the status of the species changes, new pages are sent to the subscribers. 

Green pages are used for those species that were formerly endangered, but have now recovered to a point where they are no longer threatened. With passing time, the number of pink pages continue to increase. There are pitifully few green pages.


Extinct (EX)
A taxon is Extinct when there is no reasonable doubt that the last individual has died. A taxon is presumed Extinct when exhaustive surveys in known and/or expected habitat, at appropriate times (diurnal, seasonal, annual), throughout its historic range have failed to record an individual.

Extinct in the Wild (EW)
A taxon is Extinct in the Wild when it is known only to survive in cultivation, in captivity or as a naturalized population (or populations) well outside the past range. A taxon is presumed Extinct in the wild when exhaustive surveys in known and/or expected habitat, at appropriate times (diurnal, seasonal, annual), throughout its historic range have failed to record an individual.

Critically Endangered (CR)
A taxon is Critically Endangered when the best available evidence indicates that it meets any of the criteria for Critically Endangered.

reduction in population (> 90% over the last 10 years), 
population size (number less than 50 mature individuals), 
quantitative analysis showing the probability of extinction in wild in at least 50% in their 10 years) and 
it is therefore considered to be facing an extremely high risk of extinction in the wild.

Endangered (EN)
A taxon is Endangered when the best available evidence indicates that it meets any of the criteria for Endangered.

reduction in population size (70% over the last 10 years), 
population size estimated to number fewer than 250 mature individuals, 
quantitative analysis showing the probability of extinction in wild in at least 20% within 20 years and
it is therefore considered to be facing a very high risk of extinction in the wild.

Vulnerable (VU)
A taxon is Vulnerable when the best available evidence indicates that it meets any of the criteria for Vulnerable i.e. criteria
reduction in population (> 50% over the last 10 years) 
population size estimated to number fewer than 10,000 mature individuals, 
probability of extinction in wild is at least 10% within 100 years, and 
it is therefore considered to be facing a high risk of extinction in the wild. 

Near Threatened (NT)
A taxon is Near Threatened when it has been evaluated against the criteria but does not qualify for Critically Endangered, Endangered or Vulnerable now, but is close to qualifying for or is likely to qualify for a threatened category in the near future.

Least Concern (LC)
A taxon is Least Concern when it has been evaluated against the criteria and does not qualify for Critically Endangered, Endangered, Vulnerable or Near Threatened. Widespread and abundant taxa are included in this category.

Data Deficient (DD)
A taxon is Data Deficient when there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution and/or population status. A taxon in this category may be well studied, and its biology well known, but appropriate data on abundance and/or distribution are lacking. 
Data Deficient is therefore not a category of threat. Listing of taxa in this category indicates that more information is required and acknowledges the possibility that future research will show that threatened classification is appropriate.
Not Evaluated (NE)
A taxon is Not Evaluated when it is has not yet been evaluated against the criteria.

Summary of Biodiversity

Biodiversity could hardly be defined, but can only be explained. It refers to the totality of the life forms, their genetic variability and the ecological roles they play in an ecosystem besides their interaction and interdependence in the biological communities. Value of biodiversity is measured by the health of the ecosystem. It is the key to the maintenance of natural resource, hence sustenance of organisms, including man. Deep understanding of the subject is thus required, as it provides clues for conservation.

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