Life in Tropical and Sub-tropical Regions

"The tropical and sub-tropical regions extend up to 30 degrees latitude, north and south of the Equator. These regions have warm climate and, apart from the deserts, receive abundant rainfall."

1.0Introduction

The Earth is a natural terrarium and its characteristics are differing due to different climate, location, latitude, and altitudinal condition. That is why Earth is full of uneven structure, for example dry deserts, frozen lands and hot wet rainforests.

2.0Life in the Amazon Basin

• In the map given below, notice that the tropical region lies very close to the equator; between $10^{\circ }\mathrm{N}$ and $10^{\circ }\mathrm{S}$. So, it is referred to as the equatorial region.
• The river Amazon flows through this region. Notice how it flows from the mountains to the west and reaches the Atlantic Ocean to the east. The place where a river flows into another body of water is called the river's mouth.
• Numerous tributaries join the Amazon River to form the Amazon basin. The river basin drains portions of Brazil, parts of Peru, Bolivia, Ecuador, Columbia and a small part of Venezuela.
  
  The Amazon Basin in South America

Climate

• As you now know, the Amazon Basin stretches directly on the equator and is characterized by hot and wet climate throughout the year.
• Both day and nights are almost equally hot and humid.
• The skin feels sticky. It rains almost every day, that too without much warning.
• The day temperatures are high with very high humidity.
• At night the temperature goes down but the humidity remains high.

Bromeliads are special plants that store water in their leaves. Animals like frogs use these pockets of water for laying their eggs.

Rainforests

• As it rains heavily in this region, thick forests grow.
• The forests are in fact so thick that the dense "roof" created by leaves and branches does not allow the sunlight to reach the ground.
• The ground remains dark and damp.
• Only shade tolerant vegetation may grow here.
• Orchids, bromeliads grow as plant parasites.
• The rainforest is rich in fauna.
  
  Toucans
• Birds such as toucans, hummingbirds, MACAW with their brilliantly coloured plumage, oversized bills for eating make them different from birds we commonly see in India.
• These birds also make loud sounds in the forests.
• Animals like monkeys, sloth and ant-eating tapirs are found here. Various species of reptiles and snakes also thrive in these jungles. Crocodiles, snakes, pythons abound. Anaconda and boa constrictor are some of the species.
  
  Tapir
• Besides, the basin is home to thousands of species of insects.
• Several species of fishes including the flesh-eating Piranha fish is also found in the river.
• This basin is thus extraordinarily rich in the variety of life found there.

Population dessity: It means the number of persons that live in one sq. km. of area e.g. the population density of Uttarakhand is 189 while the density of West Bengal is 1029 and that of Bihar is 1102 .

People of the Rainforests

• People grow most of their food in small areas after clearing some trees in the forest.
• While men hunt and fish along the rivers, women take care of the crops. They mainly grow tapioca, pineapple, and sweet potato.
• As hunting and fishing are uncertain it is the women who keep their families alive by feeding them the vegetables they grow.
• They practice "slash and burn agriculture".
• The staple food is manioc, also known as cassava, that grows under the ground like the potato.
• They also eat queen ants and egg sacs.
• Cash crops like coffee, maize and cocoa are also grown.
• The rainforests provide a lot of wood for the houses.
• Some families live in thatched houses shaped like beehives.
• There are other large apartment-like houses called "Maloca" with a steeply slanting roof.
• Life of the people of the Amazon basin is slowly changing.
• In the older days the heart of the forest, could be reached only by navigating the river.
• In 1970 the Trans Amazon highway made all parts of the rainforest accessible.
• Aircrafts and helicopters are also used for reaching various places.
• The indigenous population was pushed out from the area and forced to settle in new areas where they continued to practice their distinctive way of farming.
• The developmental activities are leading to the gradual destruction of the biologically diverse rainforests.
• It is estimated that a large area of the rainforest has been disappearing annually in the Amazon basin.
• You can see that this destruction of forests has a much wider implication.
• The topsoil is washed away as the rains fall and the lush forest turns into a barren landscape.

3.0Life in the Ganga-Brahmaputra Basin

• The tributaries of rivers Ganga and Brahmaputra together form the Ganga-Brahmaputra basin in the Indian subcontinent.
• The basin lies in the sub-tropical region that is situated between $10^{\circ }\mathrm{N}$ to $30^{\circ }\mathrm{N}$ latitudes.
• The tributaries of the River Ganga like the Ghaghra, the Son, the Chambal, the Gandak, the Kosi and the tributaries of Brahmaputra drain it.
  
• The plains of the Ganga and the Brahmaputra, the mountains and the foothills of the Himalayas and the Sundarbans delta are the main features of this basin.
• Ox-bow lakes dot the plain area.
• The area is dominated by monsoon climate. The monsoon brings rains from mid-June to midSeptember.
• The summers are hot and the winters cool. The basin area has varied topography.
• The environment plays a dominant role in the distribution of the population.
• The mountain areas with steep slopes has inhospitable terrain.
• Therefore a smaller number of people live in the mountain area of the Ganga-Brahmaputra basin. The plain area provides the most suitable land for human habitation.
• The soil is fertile.
• Agriculture is the main occupation of the people where flat land is available to grow crops. The density of population of the plains is very high. The main crop is paddy.
• Since cultivation of paddy requires sufficient water, it is grown in the areas where the amount of rainfall is high.

In the fresh waters of River Ganga and River Brahmaputra, a variety of dolphin locally called Susu (also called blind dolphin) is found. The presence of Susu is an indication of the health of the river. The untreated industrial and urban wastes with high amount of chemicals are killing this species.

• Wheat, maize, sorghum, gram and millets are the other crops that are grown.
• Cash crops like sugarcane and jute are also grown. Banana plantations are seen in some areas of the plain. In West Bengal and Assam tea is grown in plantations.
• Silk is produced through the cultivation of silkworms in parts of Bihar and Assam.
• In the mountains and hills, where the slopes are gentle, crops are grown on terraces.
• The vegetation cover of the area varies according to the type of landforms.
• In the Ganga and Brahmaputra plain tropical deciduous trees grow, along with teak, sal and peepal. Thick bamboo groves are common in the Brahmaputra plain.
  
  Paddy Cultivation
• The delta area is covered with the mangrove forests.
• In parts of Uttarakhand, Sikkim and Arunachal Pradesh, coniferous trees like pine, deodar and fir can be seen because the climate is cool and the slopes are steep.
• There is a variety of wildlife in the basin. Elephants, tigers, deer and monkeys are common.
• The one-horned rhinoceros is found in the Brahmaputra plain.
• In the delta area, Bengal tiger and crocodiles are found.
• Aquatic life abounds in the fresh river waters, the lakes and the Bay of Bengal Sea.
• The most popular varieties of the fish are the rohu, catla and hilsa.
• Fish and rice is the staple diet of the people living in the area.
  
  One horned rhinoceros
• The Ganga-Brahmaputra plain has several big towns and cities.
• The cities of Allahabad, Kanpur, Varanasi, Lucknow, Patna and Kolkata all with the population of more than ten lakhs are located along the river Ganga.
• The wastewater from these towns and industries is discharged into the rivers.
• This leads to the pollution of the rivers.
• All the four ways of transport are well developed in the Ganga-Brahmaputra basin.
• In the plain areas the roadways and railways transport the people from one place to another.
• The waterways are an effective means of transport particularly along the rivers.
• Kolkata is an important port on the river Hooghly.
• The plain area also has many airports.
• Tourism is another important activity of the basin.
• Taj Mahal on the banks of River Yamuna in Agra, Allahabad on the confluence of the Rivers Ganga and Yamuna, Buddhists stupas in Uttar Pradesh and Bihar, Lucknow with its Imambara, Assam with Kaziranga and Manas with wildlife sanctuaries and Arunachal Pradesh with a distinct tribal culture are some of the places worth a visit.

4.0MIND MAP

5.0Glossary

• River basin - It is the land that water flows across or under on its way to a river.
• Tributaries - These are small rivers that join the main river. The main river along with all its tributaries that drain an area forms a river basin or the catchment area.
• Slash and burn agriculture - It is a way of cultivating land where farmers clear a piece of land by slashing or cutting down trees and bushes.
• Subcontinent - A large landmass, such as India, that is part of a continent but is considered either geographically or politically as an independent entity.
• Habitation - It is a state of living somewhere.