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The Amazon biome

By: Denise Moraes

Photo: Shaan Hurley/Flickr

Photo: Shaan Hurley/Flickr

The Amazon biome takes up around 40% of the land in Brazil. It spreads across the entire states of Pará, Amazonas, Amapá, Acre, Rondônia and Roraima and a section of Maranhão, Tocantins and Mato Grosso. It also includes lands in neighbor countries such as Guyana, French Guyana, Suriname, Venezuela, Ecuador, Peru and Bolivia.

The Amazon is known for containing the world’s greatest biodiversity, with thousands of animal and plant species, as well as microorganisms. Besides the variety of life, the region includes a large number of rivers, which account for the world’s greatest surface water reserves. The climate of the region is considered to be humid equatorial. As to the terrain, there are different formations, such as plateaus and plains.

Let us take a closer look into some of the aspects of the this rich biome.

Animal life

Red-faced spider monkey*

Red-faced spider monkey*

Research indicates that there are around 30 million animal species in the Amazon. Can you believe that? And that figure only takes into account the species that were identified and studied by scientists. There are some animals there that mankind knows nothing about.

But one thing is for sure: there are a lot of animals interacting in this great ecosystem. The monkeys are probably among the most famous. There are lots of them: spider monkeys, bearded sakis, brown wooly monkeys, etc. A multitude of primates can be found hanging on branches in the Amazon. Besides them, there are other mammals that are native to the region, both terrestrial (such as jaguars, anteaters and squirrels) and aquatic (such as manatees and the Amazon river dolphin).

Reptiles have a place there as well. On a trip to the region, one may see lizards, alligators, turtles and serpents. Among amphibians, there are several types of frogs, toads and tree frogs.

Photo: Daph Chloe/Wikipedia

Photo: Daph Chloe/Wikipedia

The huge array of fish is also noteworthy: in the Amazon waters are 85% of all fish species in South America. Every year, thousands of them migrate in search of adequate places for breeding and spawning. This is called the piracema.

Other smaller creatures are also greatly important for the equilibrium of the ecosystem: the insects. And there are many of them. Beetles, ants, moths and wasps represent the majority of the animal life in the Amazon.

On land, in water, in the air. There are vast numbers of birds in the forest too. Macaws, parrots, parakeets and toucans color the canopy of trees. More than a thousand species of birds have been catalogued already.

Photo: Shao/Wikipedia

Photo: Shao/Wikipedia

Vegetation

There are three types of vegetation in the region: dry land forests, floodplain forests (the várzeas or periodically flooded forests) and igapós (constantly flooded forests).

Dry land forests occur on higher ground and, therefore, are not flooded by rivers. Sizable trees can be found there, such as the Brazil nut tree and palm trees.

Floodplain forests (várzeas) are flooded over certain periods of the year. In the most elevated parts of this forest, the inundation time is shorter and the vegetation looks like that of dry land forests. In the plains, the land is flooded for longer periods, and the vegetation looks more like that of the igapós.

Photo: DarioSanches/Flickr

Photo: DarioSanches/Flickr

But we still have to talk about the Igapós...

Igapós are the kind of vegetation of the lowest lands. They are almost always flooded. Shrubs, vines and moss are examples of common types of plants. The giant water lily Victoria amazonica , a symbol of the Amazon, is also found in the Igapós.

 

Soil

The soil in the Amazon is very sandy. It has a thin layer of nutrients formed due to the decomposition of leaves, fruits and animals. This layer is rich in humus, an organic matter that is very important for some plant species in the region.

In deforested areas, the strong rains wash nutrients out of the soil in a process called leaching, which renders the Amazon soil even poorer. Only 14% of the land in the region is considered viable for agriculture.

However, if only that much is fertile, how come are there so many trees? This is a crucial point for the balance of the ecosystem, a process in which the humus is fundamental. Besides that, nutrients are quickly absorbed by the roots of trees, which, in turn, release nutrients into the soil. It’s a constant process of recycling nutrients.

Pico da Neblina**

Pico da Neblina**

Terrain

The Amazon biome has plains (areas with a low altitude), depressions (more leveled terrain with low hills) and plateaus (elevated terrain).

The rivers recurrently flood plains. In the plateau region, there are a couple of mountain ranges, such as Taperapecó, Imeri and Parima. Brazil’s lowest (the Amazon plains) and highest (the Guianas Shield) lands are also in the Amazon. Pico da Neblina, the country’s highest point (at around 9,890 feet), is in the Guianas Shield.

Water

Because water is fundamental for life, it is always an important aspect of ecosystems. In the case of the Amazon, river water is abundant: it is the largest drainage basin on the planet. Its main river, the Amazon River, has more than a thousand tributaries (smaller rivers that flow into it), is the largest river in the world and is greatly responsible for the development of the forest.

Rivers affect the life of animals and, as you’ve already seen, the vegetation. Rivers usually have muddy, clear or black waters.

 Photo: US Forest Service

Photo: US Forest Service

The color of the water varies depending on substances found in rivers. Muddy waters, such as that of the Madeira and the Amazon rivers are rich in sediments and nutrients. The Xingu, Tapajós and Trombetas rivers have clear waters with waterfalls and stretches of white waters. These rivers do not run along land with soil rich in nutrients, such as muddy rivers, and, therefore, have clearer waters.

Finally, blackwater rivers spring out in plains and carry the sand and humus in that soil. Humus is greatly responsible for the dark color of the water. The most famous black water river in the Amazon is Rio Negro (Black river).

Climate

In the Amazon, it rains a lot and the temperature is high (usually between 71oF and 82oF). It’s the so-called humid equatorial climate, which is typical of regions close to the Equator. And how does the climate affect things? Well, taking from what we have learned until now, you are probably thinking it must affect somehow... For instance: Depending on the rain, river levels vary; if river levels increase, some areas might be flooded and, once flooded, these areas might be more or less suitable to the life of certain plants and animals.

Jaguar. Photo: Cburnett/Wikimedia

Jaguar. Photo: Cburnett/Wikimedia

Variables such as climate, terrain, soil and water affect the life of animals and plants. Wasn’t that the definition of an ecosystem (the relation between living and non-living things in a region)? Well, when we talk about the Amazon, there is yet another relationship that brings risk to the balance of the ecosystem: that between man and the forest. Let’s learn more about this relation and its consequences.

* Photo: Ana Cotta/Flickr

**Photo: Robson Czaban/Wikipedia

Learn more about other biomes and ecosystems:

The Pantanal biome

The Atlantic Rainforest biome

The Caatinga biome

Cerrado Biome

Southern Plains Biome

The Coastal Biome

Consultant:

Vânia Rocha, biologist / Museu da Vida (Fiocruz).

Source:

Linhares, Sérgio & Gewandsznajder, Fernando. Biologia Hoje - Vol 3. São Paulo: ed. Ática, 1998.

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