Did You Know?
The annual rate of deforestation of the Amazonian rainforest has been pegged at about 5,800 sq. km. in the year 2013, as compared to the loss that was recorded in 2012, which was pegged at 4,500 sq. km. The global destruction rate accounts for more than 56,000 sq. miles of tropical rainforests, which are cut down every year.
Tropical rainforests are mainly located in the equatorial regions. They are characterized by high rainfall, and have the largest biodiversity in the world. Cumulatively, they occupy an area bigger than any other type of forest. They are the most common type of rainforests, and are evenly distributed all over the world, except in Europe and Antarctica. They are located in the following continents:
- Asia: Includes Indian subcontinent and Southeast Asia (from Myanmar to Philippines)
- Australia: Northeastern regions (Queensland)
- America: South America (Amazon river basin) and Central America
- Africa: Congo river basin
- The tropical jungles of Borneo and Malaysia are very old, and may have been formed during the Pleistocene epoch more than 100 million years ago. On the basis of concentration of forests around the globe, these areas are placed at the third position.
- The Harapan rainforests of Sumatra and Indonesia are famous for the Sumatran tiger and Sumatran rhinoceros, both of which fall under the category of critically endangered species.
- Some of the famous endemic species found in these forests are the royal Bengal tiger, a flying (gliding) mammal called Colugo, Proboscis Monkey, etc.
- Over 300 species of birds are found in these tropical jungles, out of which a few endemic ones are: the Mountain Blackeye, Philippine Eagle, Crimson-headed Partridge, Silvery Kingfisher, etc.
- Numerous instances of mutual thriving among both flora and fauna can be observed in these forests. For example, the Durian tree flowers mainly undergo pollination by the Dawn Bat species.
- Due to rampant destruction and deforestation, it has been estimated that till 2100, about 50% of the current tropical forest biodiversity in Southeast Asia and a third of the current forest coverage will be wiped out, if proper efforts for conservation are not taken.
- Increase in the global demand of palm oil has led to large-scale palm tree plantations, at the cost of cutting down native tree species of the Southeast Asian forests. This has caused incessant illegal logging, ultimately affecting the entire biodiversity of the region.
Australasia and Oceania
- Belonging to the Australasian ecozone, the Queensland tropical rainforests are situated in the northeastern part of this continent. They span an area of more than 30,000 sq. km., and are divided into three sections.
- The major examples of flora include the conifers belonging to the Podocarpaceae and Araucariaceae families, and Eucalyptus tree species.
- Endemic fauna species include the Cassowary, Rainforest Kangaroos, Mountain Thornbill, Yellow Honeyeater, etc.
- In the past, these forests covered a significant area of the continent. But due to continuous deforestation, they now cover only about 2% of the entire continent.
- The Daintree Rainforest is a major part of the Wet Tropical Heritage Zone of Australia, which is included under the Queensland tropical forests. About 30% of frog, reptile, and marsupial species of Australia are found in this area.
- The Hawaiian tropical rainforest is a major example of this biome, and is included under Oceania. It is considered to be one of the wettest places on Earth, with an annual rainfall of 500 inches. These regions are categorized as coastal mesic forests, mixed mesic forests, wetlands, and bogs.
South and Central America
- The largest tropical rainforest in the world is the Amazon rainforest. It covers up to eight countries in South America, and spans an area of more than 1 billion acres.
- Thousands of floral and faunal species are seen in these jungles, and such a rich biodiversity is not present in any other corner of the world. Formed around 55 million years ago, the forest has seen infinite changes in evolution of organisms since the Eocene period.
- With reference to the flora, one of the tallest trees in the world calledKapok tree, is found in the Amazon basin. It grows to a height of more than 80 meters
- Among the fauna species, examples like jaguars, caimans, poison dart frogs, electric eels, etc., are characteristic to these regions. According to several studies, one in five species of birds and fish found all over the world are present in this region.
- A staggering number of insect species (more than 2 million) is found in the Amazon. This particular name has been given to the rainforest as the world's widest river Amazon, flows through the entire tropical region.
- The Brazilian part of the forest is experiencing an ever-increasing deforestation. Since 2005, the average rate of deforestation in this region has been more than 22,000 sq. km. per year. This is having an extensive impact on the climate of the Amazon, and is even leading to an increase in global warming levels. In the last two decades, the Brazilian rainforest has suffered two massive drought periods, which have significantly affected the biodiversity in the region.
- In Central America, tropical rainforests in countries like Costa Rica and Panama consist of about 7% of the total species of all organisms in the world. These regions are famous for the occurrence of four species of monkeys: spider, squirrel, howler, and cebus.
- The Congo river basin forms the heart of the tropical rainforest regions of this continent. The Democratic Republic of Congo accounts for more than 50% of the total forest area of Africa.
- Spanning across more than 3.5 billion sq. km., the Congo river basin rainforest experiences much less rainfall than its counterparts - Amazon and South Asian forests. The area is characterized by an average 1,800 mm. rainfall.
- These jungles were formed about 7,00,000 years ago, and hence, can be said to be one of the youngest tropical rainforest regions in the world.
- About 8,000 species of plants are found in these regions. The coconut tree species thrive in significantly large numbers in these areas, and this characteristic is not seen anywhere else in other rainforests.
- The river basin is characterized by the presence of about 2,500 species of vines and tree ferns. The latter can grow up to a height of about 30 meters.
- The major faunal species include the African Forest Elephant, Colobus Monkey, Mountain Gorillas, Pygmy Hippopotamus, etc.
- According to some studies, if the current rate of deforestation of these forests continues, they will be completely wiped off from our planet by the year 2020. Approximately every second, an area equivalent to a football field is being wiped out from these jungles.
Tropical rainforests are studied with respect to several components and related aspects. The main components of this biome are presented below.
- The ecosystem in the tropical rainforests is quite different from any other forests in the world.
- Heavy rain in these areas causes soil weathering.
- The soil is very poor in nutrients, but rich in aluminum and iron oxide.
- Most of these rainforests in the world are very old, which means that there has been an extensive usage of the available nutrients. Then, how does the soil support such a huge vegetation diversity? The answer is their rapid nutrient cycle.
- Unlike most other forests, the soil in these rainforest regions receives nutrients from the living and decaying vegetation, dead wood, decomposed animals, excreta, etc.
- Due to the abundance of decomposing agents present in these areas, the degradation of waste products is so fast that the nutrients do not penetrate the soil, and are present in the upper layers. Hence, the soil in these regions cannot be recommended for agriculture.
- More than two-thirds of the plant species around the world are found in the tropical rainforests, and hence, they are dense with vegetation.
- As soil is poor in quality, the trees have shallow roots. Broad-leaf evergreen trees are quite common in these regions.
- Trees that grow very tall (70 to 80 m) to receive the sunlight are called emergents.
- To absorb more nutrients from the soil, such trees have developed a special feature called "buttressed roots". They are the additional roots that grow from the base of the trunks, and can reach up to a height of 15 feet.
- There are also many epiphytes in these forests. They may be parasitic or symbiotic, like mosses, orchids, and numerous fungi species.
- You will find a number of carnivorous plants including the famous pitcher plant, sundew plant, rafflesia, etc. The undergrowth in these areas is less developed, as very less sunlight actually reaches the ground surface.
- Every tree and plant competes with each other for whatever sunlight that is available, and as soon as even a small amount of light reaches the surface, dense vegetation starts to thrive.
- Other examples of rainforest plants include coffee, avocado, tamarind, rubber tree, bamboo, oak, pineapple, cedar, etc.
- The plants are mostly known for their medicinal properties. One in every four pharmaceutical products are derived from the rainforest plants. About 1,400 tropical plants are believed to be effective for cancer cure.
- These regions are also one of the biggest oxygen-producing ecosystems in the world.
- More than half of the Earth's animal and insect species live in the tropical forests, and only 1% of them have ever been studied. There are over millions of species of insects. Many rare birds also live in these areas.
- Anacondas, the largest snakes in the world are mostly found in the Amazon rainforest region.
- Large pythons called Boa constrictors, and the extremely rare blue-colored morpho butterfly are found in South and Central America.
- Chlamydosaurus kingii are frilled lizards that are found in Australia.
- The blue-tongued skink is an Australian lizard found in this continent.
- Gorillas are mainly found in the African forests, while orangutans are restricted to the Indonesian and Borneo forests.
- Spider monkeys, lemurs, and howler monkeys are other examples of mammals found in these areas.
- The amphibians found here include numerous species of frogs due to the humid and damp conditions in these forests. Most species have still not been discovered. For example, poison dart frogs are one of the most poisonous ones in the world.
- Birds like macaws, parrots, toco toucans, etc., are mainly found in the tropical forests.
- The endangered animals found in these forests include the Javan and Sumatran rhinoceros, jaguar, giant otter, Proboscis monkey, etc.
- Other rainforest animals include red lizards and black tarantulas.
Climate and Temperature
- The climate in tropical rainforests is hot and humid, and the temperatures hover around 80° F for most of the year.
- These regions receive around 100 to 400 inches of rain in a single year, and changes in weather are rarely observed.
- The climate of these regions is controlled by a particular type of wind-front called Intertropical Convergence Zone.
- Annual rainfall of around 800 cm. causes the forest floor to permanently remain wet, and hence, decomposition rate on the surface increases.
- The Amazonian rainforests produce about 20% of the world's oxygen, and hence, they are also known as the lungs of the Earth.
- This causes a significant effect on the global climate, as the rainforests act as a gigantic carbon dioxide sink, leading to the decrease in global warming.
- Currently, these areas are experiencing a temperature increase of approximately 0.30° C per year, due to the greenhouse gas effect.
- Also, due to increase in the El Niño activity in the equatorial regions since a few decades, rainforests have been experiencing drastic variations in climate and temperatures, leading to drought seasons and dry spell intensity during the monsoon.
- Though most of the tropical rainforests are covered by the emergent and canopy layer of tall trees and other plants, these regions are also characterized by a variety of landforms and geological features.
- Of all the mountains in the world, about 22% are found in the Amazon rainforest of South America. Other mountain ranges are also present in various rainforest areas of Africa, Central America, Indonesia, Malaysia, Borneo, etc.
- Inselbergs are a characteristic feature of these forests. They are massive isolated rocks and boulders, which have formed due to weathering of less resistant minerals and sediments, leaving behind these outcrops. For example, large granite inselbergs are found in the Congo basin rainforest region of Central Africa.
- V-shaped and U-shaped valleys are important geological structures found in these regions. They allow the formation of river and stream courses, and ultimately lead to the floodplain areas.
- Wetlands are one of the most important landforms of tropical rainforest areas, as they annually receive a large amount of rainfall, leading to formation of bogs, swamps, marshes, etc. The soil in such areas is saturated with water, and not fit for agriculture.
- Floodplains are the areas that get inundated due to sudden increase in river water volume, as a result of heavy monsoon. They are formed due to the joining of two or more rivers at a junction.
Around 40% of tropical rainforests have already been cut down in Latin America and Southeast Asia. If proper measures are not taken to save these areas, we will lose the most valuable source of pharmaceutical products, as well as the wide variety of floral and faunal species found in these regions. They play a crucial role in maintaining the ecological balance, and are extremely necessary for our survival. Protecting these forests is of vital importance.