Environment Notes

Tropical rainforests: Characteristics, Location, Flora & Fauna

Tropical Rainforests: Hub of Biodiversity

Tropical rainforests are some of the most vibrant and biologically diverse ecosystems on Earth. They are characterized by high levels of rainfall, with annual precipitation often exceeding 2000 mm (about 78 inches), and are typically found near the equator, within the latitudinal belt of 10°N to 10°S. These forests cover about 7% of the Earth’s surface but harbor more than half of the world’s plant and animal species. The Amazon rainforest in South America is the largest tropical rainforest in the world.

Ecological Conditions

1. Climate: Tropical rainforests experience a warm and humid climate with relatively stable temperatures throughout the year, usually ranging from 20°C to 25°C (68°F to 77°F). The high humidity, often between 77% and 88%, and substantial rainfall contribute to the lush vegetation and diverse wildlife found in these forests.

2. Soil: Despite the rich biodiversity, the soils in tropical rainforests are often poor in nutrients. This is because the constant warm temperatures and moisture accelerate the decomposition of organic matter, which is quickly absorbed by the dense vegetation. Nutrients are not stored in the soil for long. The top layer of soil, known as the O horizon, is rich in organic material, but the underlying layers are less fertile.

3. Canopy Structure: The forest structure is stratified into different layers, each with distinct plant and animal life adapted to its specific conditions. The emergent layer consists of the tallest trees that rise above the general canopy, reaching heights of up to 70 meters (230 feet). The canopy layer forms a dense roof over the forest and is home to a majority of the forest’s wildlife. Below the canopy is the understory, a shadowy, cooler environment with smaller trees and shrubs. The forest floor receives minimal sunlight and is covered with decomposing plant and animal matter.

4. Biodiversity: Tropical rainforests are renowned for their biodiversity. They provide habitat for a vast array of species, including numerous types of trees, plants, mammals, birds, reptiles, amphibians, and insects. Many species are endemic, meaning they are found nowhere else in the world. This high level of biodiversity is due to the constant climate, which has remained relatively unchanged for millions of years, allowing species to evolve and adapt over long periods.

5. Water Cycle: Tropical rainforests play a crucial role in the global water cycle. The dense vegetation transpires a significant amount of water, contributing to the formation of clouds and precipitation not only within the forest but also in regions far away. This process, known as evapotranspiration, helps regulate the Earth’s temperature and moisture levels.

6. Carbon Sequestration: These forests are vital in the global carbon cycle. They absorb large amounts of carbon dioxide from the atmosphere through photosynthesis, making them significant carbon sinks. This helps mitigate climate change by reducing the concentration of greenhouse gases in the atmosphere.

Major Tropical Rainforests and Their Biodiversity

Tropical rainforests are found in several regions around the world, each with its unique flora and fauna. Here are some of the major tropical rainforests, their locations, and examples of their biodiversity:

1. Amazon Rainforest

Location: Spread across nine countries in South America, with the majority in Brazil.
Flora: Home to over 40,000 plant species, including the rubber tree (Hevea brasiliensis), various orchids, and giant water lilies (Victoria amazonica).
Fauna: Hosts a diverse range of wildlife, including the jaguar (Panthera onca), Amazon river dolphin (Inia geoffrensis), sloths, several species of monkeys, and over 1,300 bird species like the harpy eagle (Harpia harpyja).

2. Congo Rainforest

Location: Central Africa, primarily in the Democratic Republic of Congo.
Flora: Contains about 10,000 plant species, with mahogany trees, ebony, and the Congo peacock (Afropavo congensis) being notable.
Fauna: Rich in biodiversity, including forest elephants (Loxodonta cyclotis), lowland gorillas (Gorilla gorilla gorilla), okapi (Okapia johnstoni), and the bonobo (Pan paniscus).

3. Southeast Asian Rainforests

Location: Covers parts of Indonesia, Malaysia, Thailand, Myanmar, and the Philippines.
Flora: Known for the Rafflesia arnoldii, the world’s largest flower, teak trees, and various species of bamboo and rattan.
Fauna: Home to the orangutan (Pongo spp.), Sumatran tiger (Panthera tigris sumatrae), Asian elephant (Elephas maximus), and the critically endangered Javan rhinoceros (Rhinoceros sondaicus).

4. Daintree Rainforest

Location: Northeast coast of Queensland, Australia.
Flora: One of the oldest rainforests, with ancient ferns, epiphytic plants, and the unique Idiot Fruit tree (Idiospermum australiense).
Fauna: Habitat for the cassowary (Casuarius casuarius), the musky rat-kangaroo (Hypsiprymnodon moschatus), and the Ulysses butterfly (Papilio ulysses).

5. Madagascar Rainforests

Location: Eastern coast of Madagascar.
Flora: Known for its high level of endemism, including the traveller’s tree (Ravenala madagascariensis), various species of Baobabs, and over 10,000 endemic plant species.
Fauna: Famous for its lemurs (over 100 species), the fossa (Cryptoprocta ferox), and numerous unique bird species like the Madagascar fish-eagle (Haliaeetus vociferoides).

6. Central American Rainforests

Location: Stretching from southern Mexico through Central America.
Flora: Contains mahogany trees, ceiba (the national tree of Guatemala), and various orchids.
Fauna: Home to the jaguar, Baird’s tapir (Tapirus bairdii), the resplendent quetzal (Pharomachrus mocinno), and the scarlet macaw (Ara macao).

Each of these rainforests plays a crucial role in maintaining global biodiversity, climate regulation, and the water cycle. Their unique ecosystems are a result of millions of years of evolution, leading to a high degree of endemism and diversity. However, they are all facing threats from deforestation, climate change, and human encroachment, highlighting the need for concerted conservation efforts.