The Amazon rainforest is the largest continuous rainforest ecosystem in the world. The ecosystem includes the drainage basin for the Amazon River. The river itself is over 4,000 miles long and is at the centre of the functioning of this ecosystem. The land base is nearly the size of the lower 48 states of the U.S. Little seasonal climate change occurs during the year. The average temperature is about 25.6 degrees C, with heavy rainfall occurring throughout the year. These climatic conditions have a direct impact on the ecosystem.
The land, the river, and its climate contribute to the vast biodiversity of the Amazon rainforest. A 2005 study published in the journal Conservation Biology estimated that Brazil, which includes over half of the entire rainforest, has over 170,000 different species of known organisms. According to the Nature Conservancy, a four-square mile section of rainforest may contain over 400 species of birds alone. The warm, humid climate creates the ideal conditions for plant growth.
The Amazon rainforest, like others, has a unique ecological structure which influences the interactions and relationships which occur in this ecosystem. It is composed of five layers, each with its own unique plant life and thus, wildlife which inhabit each layer. The top two layers consist of trees which form the forest canopy. The canopy forms a dense layer overhead, shading the third layer of the lowest trees. The fourth layer includes shade-tolerant shrubs, while the fifth and lowest layer consists of low herbaceous plants. Birds and bats are found at the top layers. Insects inhabit lower layers, with the large mammals found at ground level.
The plants of the Amazon rainforest show their diversity and adaptability. The structure of the rainforest allows the plants to find their own unique ecological niches. The Nature Conservancy further reports that a four-square mile area contains over 1,500 species of flowering plants and up to 750 species of trees. Unfortunately, while these figures may sound significant, they represent only a fraction of the true picture. Only a small percentage of the Amazon's plant life has been documented or studied for their potential medicinal value. Much of the ecology of this ecosystem remains unknown.
Like plants, the birds and bats of the Amazon rainforest adapted to the variety of niches and food resources available to them. A 2005 study also published in Conservation Biology reported that the Amazon rainforest has over 1,200 species of birds. Diversity is also evident in other wildlife, with an estimated 427 mammal species, 378 reptiles and 427 amphibians.
Despite its vast size, the Amazon rainforest ecosystem faces environmental pressure that threatens its very existence. One of the primary threats is deforestation. Since 1970, over 200,000 square miles of Amazon rainforest have been lost due to deforestation, according to Monga Bay. The rainforest soils are poor, lacking in fertility. Most of the nutrients are locked in the above ground plant growth. Due to the ecology of the ecosystem, recovery is difficult, if not impossible.
- Greatest Places: Amazon Basin
- "Ecology and Field Biology;" Robert Leo Smith; 1990
- Conservation Biology: "How Many Species Are There in Brazil?;" T. Lewinsohn and P. Prado; June 2005
- Nature Conservancy: Rainforests
- Conservation Biology: "The Fate of the Amazonian Areas of Endemism;" J.Cardoso da Silva, A. Rylands, and G. da Fonseca; June 2005