Environmental Science

LESSON 9. Biogeographic Classification Of India

India’s Biogeographic Zones are given below :

1. The cold mountainous snow covered Trans-Himalayan region of ladakh

2. The Himalayan ranges and valleys of Kashmir, Himachal Pradesh, Uttarakhand, Assam and other North eastern States.

3. The Terai, the low land where the Himalayan rivers flow into the plains

4. The Gangetic and Brahmaputra plains.

5. The Thar Desert of Rajastan

6. The semi- arid grassland region of the Deccan plateau, Gujarat, Maharashtra,Andhra Pradesh, Karnataka and Tamilnadu

7. The North eastern States of India

8. The Western Ghats in Maharastra, Karnataka and Kerala

9. The Andaman and Nicobar Islands

10. The long western and eastern coastal belt with sandy beaches, forests and mangroves.

THREATS TO BIODIVERSITY:

Habitat loss is mainly due to human population growth, industrialization and changes in the land use patterns, poaching of wild life and man wildlife conflicts. Man has begin to overuse or misuse most of these natural ecosystems. Due to unsustainable resource-use, once productive forests and grasslands have been turned into deserts and wastelands have been increased all over world. Scientists have estimated that human activities are likely to eliminate approximately 10 million species by the year 2050.

 Human population growth, industrialization and changes in the land use patterns:

Around 1.8 million species of plants and animals are known to science. The actual number of species have been existing is  more than 10x1.8millions. Though new species have been continually identified, the rate of extinction is very high (10-20,000 species per year i.e.,1000 to 10,000 times faster rate). Human actions are expected to exterminate 25% of world’s species in next 20-30 years. The mega extinction spasm is related to human population growth, industrialization and changes in the land use patterns in India. The reasons are:

1. Forests and grasslands are changed to agricultural land. Encroachments are being repeatedly legalized.

2. Natural wetlands are drained to establish crop lands leading to loss of aquatic species.

3. Mangroves have been cleared for fuel wood and prawn farming, which has led to decrease in the habitat essential for breeding of marine fish.

4. Grasslands are changed to other forms, degraded by overgrazing. Loss to cattle, goat and sheep.

5. Natural forests are being deforested for timber and replanted for teak, sal etc. Such monoculture does not support biodiversity as in forests which has closed canopy and rich undergrowth. Excess collection of fire wood by lopping of branches of trees canopy is opened up altering the local biodiversity.

6. Foraging cattle retard regeneration of forest as young seedlings are trampled.

7. Ever increasing population gradually decrease buffer zones and forested areas. A prime example is Gir national park, the last bastion of Asiatic lion with a meter gauge railway line, state expressway and 3 temples.

8. Repeated fires by local grazers to increase growth of grass ultimately reduce regeneration of grasses.

9. Introduction of exotic weeds eg. lantana bushes, Eupatorium shrubs and ‘congress’ grass are invading at the expense of indigenous undergrowth species. Following traditional farming techniques like slash and burn in Himalayas, and rab, lopping of tree branches for making wood ash fertilizer in Western ghats

   are now leading to loss of biodiversity.

10. Over harvesting of fish by large trawling boats is leading to depletion of fish stocks.

Marine turtles caught in the net are massacred of the coast of Orissa. The rare whale shark, a highly endangered species, is being killed off the coast of Gujarat.

 Poaching:

Specific threats to certain animals are related to large economic benefits. The skin and bones from tigers, ivory from elephants, horns from rhinos and perfume from the musk deer are extensively used abroad. Bears are killed for their gall bladders. Corals and shells are also collected for export or sold on the beaches of Chennai, Kanyakumari and the Andaman and Nicobar islands. Tortoises, exotic birds and other small animals are packed into tiny containers and smuggled abroad for the pet trade. A variety of wild plants with real or sometimes, dubious medicinal values are being overharvested. The commonly collected plants include Rauwolfia, Nux vomica, Datura, etc. The garden plants collected for illegal trade include orchids, ferns and mosses.

 Man wild life conflicts:

Conflicting situations with wild life starts causing immense damage and danger to man. Ex: In Sambalpur, Orissa 195 humans are killed in last 5 years by elephants and in retaliation villagers killed 98 elephants and badly injured more than 30 elephants. Similar incidents with tigers, leopards etc. are in news. Shrinking forest cover, human encroachment, ill and weak animals, lack of food (one adult elephant needs 200 kg green fodder and 150 kg of clean water) for animals, protecting villagers by putting electric fence are the main reasons for such happenings. As the compensation by government. is not enough, conflicts occur between forest department and villagers.