Chapter: Environmental Science and Engineering


Biodiversity is the variety and differences among living organisms from all sources, including terrestrial, marine, and other aquatic ecosystems and the ecological complexes of which they are a part.




v   Biodiversity is the variety and differences among living organisms from all sources, including terrestrial, marine, and other aquatic ecosystems and the ecological complexes of which they are a part.


v   It is virtually synonymous with “Life on earth”.


v   Biologists most often define "biological diversity" or "biodiversity" as the "totality of genes, species, and ecosystems of a region".


v   The biodiversity found on Earth today consists of many millions of distinct biological species, which is the product of nearly 3.5 billion years of evolution.


1 Levels of Biodiversity


1) Genetic diversity


v   It is a level of biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species.


v   It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary.


2) Species diversity

v   It refers to the variety of species within a region.


v   Species diversity is an index that incorporates the number of species in an area and also their relative abundance.


v   It is generally a much more useful value than species richness.


3) Community and Ecosystem diversity


v   Ecosystem diversity refers to the diversity of a place at the level of ecosystems. This has 3 perspective:


v   Alpha Diversity: Within community diversity. Alpha diversity refers to the diversity of organisms sharing the same Community/Habitat.

 v   Beta Diversity: Between community diversity. It refers to the diversity of organisms sharing two habitats.


v   Gamma Diversity: Diversity of the habitat over the total landscape or geographical area is called gamma diversity.


2 Values of Biodiversity


Food: About 80,000 edible plants and about 90% of present day food crops have been domesticated from wild.


Drugs & Medicines: About 75% of world’s population depends on plants or plant extracts.


Fuel: Forests have been used since ages for fuel wood. Fossil fuels are also products of Biodiversity.


Social Value: Many of the plants like Tulsi, Lotus, Peepal etc are considered holy and sacred.


v   About 2.1 million species have been identified till date, while many more species are believed to exist.


v   According to UNEP estimate, approximately 9.0 – 52 million of species exist on Earth


v   India’s position is 10th in the world & 4th in Asia in terms of Plant diversity.




v   A biodiversity hotspot is a biogeographic region with a significant reservoir of biodiversity that is threatened with destruction.

v   An area is designated as a hot spot when it contains at least 0.5% of plant species as endemic.


v   There are 25 such hot spots of biodiversity on a global level, out of which two are present in India.


v   These are: Indo- Burma (earlier The Eastern Himalayas) ,The western Ghats & Sri Lanka..


v   These hot spots covering less than 2% of the world’s land area are found to have about 50% of the terrestrial biodiversity.


Criteria for determining hot-spots

v   No. of Endemic Species i.e. the species which are found no where else.

v   Degree of threat, which is measured in terms of Habitat loss.


E.g. Indo- Burma (Eastern Himalayas) Hotspot


v   The hotspot includes all of Cambodia, Vietnam & Laos, and nearly the entire areas of Thailand, Myanmar & Bhutan as well as part of Nepal, far eastern India and extreme southern China.


v   In addition, it covers several offshore Islands including Mainan Islands in the south China Sea and Andaman & Nicobar Islands in Indian Ocean.


v   Indo-Burma is one of the most threatened biodiversity hotspots, due to the rate of resource exploitation and habitat loss.


E.g. Western Ghats and Sri Lanka


v   Western Ghats and Sri Lanka, also known as the “Sahyadri Hills” encompasses the montane forests in the southwestern parts of India and on the neighboring Islands of Sri Lanka.



v   The entire extent of hotspot was originally about 1,82,500 square kms, but due to tremendous population pressure, now only 12,445 square Km or 6.8% is in pristine condition.


v   The important populations include Asian elephant, Indian tigers and the endangered lion tailed macaque.



v   Extinction is a natural event and, from a geological perspective, routine.


v   In last century, human impact has been so severe that thousands of species and varieties are becoming extinct annually.


v   Some of the main causes are:


v   Habitat loss, degradation, fragmentation.


v   Habitat loss & degradation are major causes of species extinction, affecting 89% of all threatened birds, 83% of mammals & 91% of all threatened plants assessed globally (IUCN, 2000)


v   The main causes of habitat are agriculture activities, Mining, development of human settlement, industry etc.


v   According to ICUN, UNEP report, more than 50% of wildlife habitat has been destroyed in 49 out of 61 old world tropical countries.




v   Poaching is another threat that has emerged in recent decades as one of the primary reason for decline in number of species.


v   Wildlife is sold and traded in many countries for live specimens, folk medicines, furs, Skin, and other products such as Ivory, horns etc amounting to millions of dollars.




v   The conflict between man and wildlife started with the evolution of man, but intensity increased due to the activities of modern man


v   Due to the lack of stable food and disruption of movement, wild animals came out of forest area and attack the agricultural field and humans and in turn got killed by the humans.


1 Introduction of Exotic species

v   Organisms introduced into habitats where they are not native are termed as exotics.


v They can be thought of as Biological Pollutants and are considered to be among the most damaging agents of habitat alteration and degradation the world.


2 Climate change

A changing global climate threatens species and ecosystems.

v   The distribution of species (biogeography) is largely determined by climate.


v   Climate change may simply shift these distributions but, for a number of reasons, plants and animals may not be able to adjust.





v   According to The International Union of Conservation of Nature and Natural Resources (IUCN), the species that considered in imminent danger of extinction and whose survival is unlikely, if factors causing their decline continue to operate.


v   Out of about 47,000 species of plants in our country, 7000 are endemic


v   India contains 172 species of animals considered globally threatened by IUCN, or 2.9% of the world’s total number of threatened species.


v   These include 53 species of mammals, 69 birds, 23 reptiles and 3 amphibians


v   As many as 3,000- 4,000 higher plants may be under high degree of threat in India


v   Thus Indian subcontinent has about 62% endemic flora, restricted mainly to Himalayas, khasi Hills & Western Ghats.


v   Sapria himalayana, Uvaria lurida, Napenthes khasians etc. are some endemic flora of our country.


v   A large number out of a total of 81,000 species of animals in our country is endemic. About 62% amphibians and 50% lizards are endemic to western Ghats.


v   Golden monkey, Niligiri Langur, Indian Wolf, Red Fox, Himalayan Brown Bear, Great Indian One Horned Rhinoceros, White Winged Wood Duck, Black Necked Crane, Indian Pea Fowl, Gharial, Indian egg eating Snake, Indian Salamandar etc. are some examples of endemic animal species of India.




v   The convention on Biological Diversity held in June, 1992 stressed the need of the conservation of Biodiversity for sustainable development and perpetuation of human beings on earth.


v   Conservation is defined as “ the management of human use of the biosphere so that it may yield the greatest sustainable benefit to the present generation while maintaining its potential to meet the needs and aspirations of the future generations”.


v   The two basic approaches to wildlife conservation in protected habitats are:


1) In- situ conservation 2) Ex- situ conservation.


1 In- situ conservation


v   It simply means conservation of species in its natural ecosystem or even in man made ecosystems.

v   This strategy emphasizes protection of total ecosystem through a network of “protected area”.


v   Protected Areas: an area of land and/or sea specially dedicated to the protection and maintenance of biological diversity and managed through legal effective means.


v   There are different categories of protected areas which are managed with different objectives. These include; Biosphere reserves, National parks, Wild Life Sanctuaries etc.


v   At present we have 11 major biosphere reserves, 80 National parks, 420 wildlife sanctuaries in our country covering 4% of the geographic area.

v   The JIM CORBETT National Park was 1st national park established in India.


What is Difference among Biosphere reserves, National parks, Wild Life Sanctuaries ? Examples of Biosphere reserves of India:


1.     Nilgiri- 5,520


2.     Nanda Devi- 5,860.69 sq. km


3.     Manas – 2837 sq. km


4.     Gulf of Mannar – 10,500 sq. km


5.     Great Nicobar – 885 sq. km


6.     Panchmarhi – 4,926.28 Sq Km Examples of some National park in India


1. Kaziranga- Assam, Gir National Park- Gujarat, Periyar – Kerala, Sariska – Rajasthan Examples of some Wild Life Sanctuaries of India:


1.     Ghana Bird sanctuaries


2.     Hazaribagh sanctuaries


3.     Abohar wild life sanctuaries


4.     Jaldapara wild life sanctuaries


5.     Mudamalai wild life sanctuaries


2 Ex- situ conservation


v   It is defined as “the conservation of component of biological diversity (Sample of genetic diversity, particularly of endangered species) outside their natural habitats”.


v   It involves maintenance and breeding of endangered plant and animal species under partially or wholly controlled conditions. E.g. Zoos, Botanical Gardens, Aquaria, Nurseries, DNA bank, Seed bank, Gene bank etc.


v   There are more than 1500 Botanical gardens in the world containing more than 80,000 species.


v   There are more than 800 zoos around the world with about 3,000 species of mammals, birds, reptiles and amphibians.


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