BIO – DIVERSITY & ITS CONSERVATION
PART 3
EXTINCTION OF SPECIES :
• The most serious aspect of the loss of biodiversity is the extinction of species.
• Once a species goes extinct, its chances for further evolution are lost.
• A species is considered extinct, when no member of the species remains alive anywhere in the world.
• If individuals of a species remain alive only in captivity or other human-controlled conditions, the species is said to be extinct in the wild.
• In both of these situations, the species would be considered globally extinct.
• A species is considered to be ecologically extinct, if it persists at such reduced numbers that its effects on other species in its community are negligible. Extinction is a natural process.
Types of extinction : Species become extinct through three types of extinction processes.
1. NATURAL EXTINCTION :
• It is the extinction of species slowly from the earth due to change in environmental conditions.
• Some species disappear and the others which are more adapted to changed conditions, take their place.
• Many species have lost in the geological past by natural extinction. The extinction of species in the geological past is also called background extinction.
2. MASS EXTINCTION :
• It refers to the extinction of large number of species due to catastrophe. There have been several periods in the earth's geological history, when large number of species became extinct because of catastrophes. Mass extinction occurred in millions of years.
3. ANTHROPOGENIC EXTINCTION :
• They are extinctions abetted by human activities like settlements, hunting, over exploitation and habitat destruction.
• The World Conservation Monitoring Centre has found out that since 1600 A.D., the earth has lost 533 animal species (mostly vertebrates) and 384 plant species (mostly flowering plants).
• 75% of these extinctions are caused by direct human interference. It is almost documented that Dodo (Raphus cucullatus) and Taswania Wolf (Thylacinus cyanocephalus) have been hunted to extinction by humans.
SUSCEPTIBILITY OF EXTINCTION :
All species are not equally susceptible to extinction. The characteristics which make a species susceptible to extinction are listed below
(i) Large body size e.g. Bengal tiger, lion and elephant.
(ii) Small population size and low reproductive rate e.g. Blue whale and Giant Panda.
(iii) Feeding at high tropic levels in the food chain e.g. Bengal tiger and Bald eagle.
(iv) Fixed migratory routes and habit. e.g. Blue whale and whooping crane.
(v) Localized and narrow range of distribution. e.g. Woodland caribou and Island species.
RED DATA BOOK AND IUCN :
• IUCN is International Union of Conservation of Nature and Natural Resources which is now called World Conservation Union (WCU).
• It has its headquarters at Morges, Switzerland. It maintains a red data book or red list which is a catalogue of taxa facing risk of extinction.
• Threatened species is the one which is liable to become extinct if not allowed to realise its full biotic potential by providing protection from exotic species/human exploitation/habitat deterioration/depletion of food. Red data book or red list was initiated in 1963.
Out of these, four categories of species are included threatened species - critically endangered, endangered, vulnerable and lower risk species.
Two more categories are also added to them.
(i) Rare Species (R): They are species with naturally small population, either localised or thinly scattered, which are always at risk from pests/pathogens/predators/exotic species. Clouded Leopard (Neofelis nebulosa). Hawaiian Monk Seal (Monochus schauinslandii). Great Indian Bustard (Ardeotis nigriceps).
(ii) Indeterminate Species : The species are in danger of extinction but the reason is not known, e.g., 3-banded Armadillo of Brazil, Short Eared Rabbit of Sumatra, Mexican Prairie Dog.
The main objectives of Red lists are listed below :
a. Identification and documentation of endangered species.
b. Providing a global index of the decline of biodiversity.
c. Developing awareness about the importance of threatened biodiversity.
d. Defining conservation priorities at the local level and guiding conservation action.
• The most serious aspect of the loss of biodiversity is the extinction of species.
• Once a species goes extinct, its chances for further evolution are lost.
• A species is considered extinct, when no member of the species remains alive anywhere in the world.
• If individuals of a species remain alive only in captivity or other human-controlled conditions, the species is said to be extinct in the wild.
• In both of these situations, the species would be considered globally extinct.
• A species is considered to be ecologically extinct, if it persists at such reduced numbers that its effects on other species in its community are negligible. Extinction is a natural process.
Types of extinction : Species become extinct through three types of extinction processes.
1. NATURAL EXTINCTION :
• It is the extinction of species slowly from the earth due to change in environmental conditions.
• Some species disappear and the others which are more adapted to changed conditions, take their place.
• Many species have lost in the geological past by natural extinction. The extinction of species in the geological past is also called background extinction.
2. MASS EXTINCTION :
• It refers to the extinction of large number of species due to catastrophe. There have been several periods in the earth's geological history, when large number of species became extinct because of catastrophes. Mass extinction occurred in millions of years.
3. ANTHROPOGENIC EXTINCTION :
• They are extinctions abetted by human activities like settlements, hunting, over exploitation and habitat destruction.
• The World Conservation Monitoring Centre has found out that since 1600 A.D., the earth has lost 533 animal species (mostly vertebrates) and 384 plant species (mostly flowering plants).
• 75% of these extinctions are caused by direct human interference. It is almost documented that Dodo (Raphus cucullatus) and Taswania Wolf (Thylacinus cyanocephalus) have been hunted to extinction by humans.
SUSCEPTIBILITY OF EXTINCTION :
All species are not equally susceptible to extinction. The characteristics which make a species susceptible to extinction are listed below
(i) Large body size e.g. Bengal tiger, lion and elephant.
(ii) Small population size and low reproductive rate e.g. Blue whale and Giant Panda.
(iii) Feeding at high tropic levels in the food chain e.g. Bengal tiger and Bald eagle.
(iv) Fixed migratory routes and habit. e.g. Blue whale and whooping crane.
(v) Localized and narrow range of distribution. e.g. Woodland caribou and Island species.
RED DATA BOOK AND IUCN :
• IUCN is International Union of Conservation of Nature and Natural Resources which is now called World Conservation Union (WCU).
• It has its headquarters at Morges, Switzerland. It maintains a red data book or red list which is a catalogue of taxa facing risk of extinction.
• Threatened species is the one which is liable to become extinct if not allowed to realise its full biotic potential by providing protection from exotic species/human exploitation/habitat deterioration/depletion of food. Red data book or red list was initiated in 1963.
Out of these, four categories of species are included threatened species - critically endangered, endangered, vulnerable and lower risk species.
Two more categories are also added to them.
(i) Rare Species (R): They are species with naturally small population, either localised or thinly scattered, which are always at risk from pests/pathogens/predators/exotic species. Clouded Leopard (Neofelis nebulosa). Hawaiian Monk Seal (Monochus schauinslandii). Great Indian Bustard (Ardeotis nigriceps).
(ii) Indeterminate Species : The species are in danger of extinction but the reason is not known, e.g., 3-banded Armadillo of Brazil, Short Eared Rabbit of Sumatra, Mexican Prairie Dog.
The main objectives of Red lists are listed below :
a. Identification and documentation of endangered species.
b. Providing a global index of the decline of biodiversity.
c. Developing awareness about the importance of threatened biodiversity.
d. Defining conservation priorities at the local level and guiding conservation action.
To be Continued in Part 4
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