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The Atlantic Rainforest biome

Por: Denise Moraes

Tijuca Forest(1)

Tijuca Forest(1)

Let’s go back to our history books before we talk about a biome that played a very important role in Brazil’s history even before it was classified as a biome.

When the Portuguese reached the shores of Brazil in 1500, they saw a very different coast from their caravels. As the scribe Pero Vaz de Caminha wrote in a letter to the king of Portugal:

“Toward eventide, we sighted land! Firstly, a large mountain, very tall and round; then other, lower hills, lying southward of the mountain, and beyond that, flat land. And mighty woods.”

What Caminha and his fellow crew members saw from their ships was the environment we now call the Atlantic Rainforest, so named precisely because it lies near the Atlantic Ocean. Smooth, rounded hills, flat lands, and massive forests are typical of this biome, which today covers only 8% of the territory it occupied when the Portuguese arrived.

The Atlantic Rainforest follows the Brazilian coast from the Northeast state of Rio Grande do Norte to the southernmost state, Rio Grande do Sul, spreading across seventeen states in all. Since this biome is found in very different areas of Brazil, it contains different ecosystems, with different varieties of fauna, flora, soil, topography, and climate. But all of the Atlantic Rainforest has some features in common. We’ll focus on these things, so you can learn more about this jewel that enchanted the colonizers so much.

Wooly spider monkey(2)

Wooly spider monkey(2)

Fauna

Some 260 species of mammals, 620 species of birds, and 260 species of amphibians have been found in the Atlantic Rainforest, not to mention many reptiles and insects. The forest shelters 383 of Brazil’s 633 endangered species, including the golden lion tamarin, which loves to swing from tree to tree.

Other mammals live in these woods as well. Sloths, opossums, bats, ferrets, saki monkeys, and pacas are common to this environment, which is home to another surprise: the wooly spider monkey, the biggest monkey on this continent.

The most notable of the reptiles are broad-nosed caymans, fresh-water turtles, coral snakes, and black lizards (teiús)—a species of lizards that can grow to more than one meter in length (3.2 ft). The most common birds include tanagers, woodpeckers, piping guans, bellbirds, and hawks.

Flora

To help them study the forest’s plantlife, researchers classify flora in strata, or layers. The tallest trees—the ones that get the most sun—belong to the highest stratum. Called the canopy, this stratum is where we find trees like the manacá-da-serra (Tibouchina mutabilis) and the Brazilian firetree (Schizolobium parahyba).

The understorey lies just beneath the canopy, inside the woods; this is where we find species living in the shade of the taller trees. The understorey is home to trees like the jaboticaba (also called the Brazilian grape tree), the juçara palm, begonias, jatobas, Brazilian glory trees, and the ipê (also known as the trumpet tree).

The lowest stratum is called the shrub layer, which is made up of small plants that lie close to the ground. This includes small bushes, herbs, grasses, and mosses.

Brazilwood (3)

Brazilwood (3)

While trees in the canopy get most of the sunlight and then the plants in the understorey capture a bit of it too, how much is left for the shorter plants, which grow inside the dense forest?

There’s not much sun left, but there is some. Plants found in the lower layers have adapted by growing large leaves and increasing the amount of surface that can capture sunlight.

Brazilwood, which is hard to find nowadays, used to be a very common plant. It was the first thing Portuguese explorers went after because they could extract a substance called “brasileína” from the tree and use it to make a red dye.

 Serra do Mar. Foto: Ibama

Serra do Mar. Foto: Ibama

Topography

The Atlantic Rainforest runs along the entire stretch of the coastal plains and into the coastal mountain range. This range is known by different names in the various regions it cuts through. In Southeast Brazil, for example, a length of it is called the Serra do Mar.
Serra do Mar.

Between the plains and the mountains lie rounded hills. The hill that caught Pero Vaz de Caminha’s eye is called Monte Pascoal (Easter Mountain), and it is located in the state of Bahia. With an elevation of 586 meters (1,922 ft), the mountain got its name because the Portuguese arrived around Easter time.

Atlantic rainforest soil, Ipatinga, MG(4)

Atlantic rainforest soil, Ipatinga, MG(4)

Soil

The soil in this forest is generally quite shallow, not well drained, always moist, and receives very little light, since—as we have already seen—most of the sunlight is absorbed by the leaves of the tallest trees.

The soil is poor but its fertility is guaranteed by something called the undergrowth: a layer covering the surface of the soil that is formed of old vegetation, like leaves, stalks, and fruit peels.

The decomposition of this vast quantity of organic matter guarantees the recycling of nutrients in this environment. The nutrients found in the undergrowth are absorbed by the soil and go back into the plants, in a cycle that ensures this biome’s lush plantlife.

Iguazu Falls(5)

Iguazu Falls(5)

Water

The Atlantic Rainforest holds enough water to supply the needs of 70% of the Brazilian population. The rivers that pass through the biome are part of seven of the country’s nine hydrographic basins.

We’re talking about a very humid forest. The rain that runs down the leaves and trunks and accelerates soil decomposition also filtrates into the soil and feeds the groundwater, which can in turn form springs and riverheads. Rivers are also fed by rain water and their courses can even be altered by heavier rains.

Climate

Since the Atlantic Rainforest is spread all along the Brazilian coast, it is home to different types of climate. Some southern stretches of the forest lie in moist subtropical climates, while other areas lie in a tropical climate region and still others are found very close to Northeast Brazil’s semi-arid caatinga.

But all regions of the Atlantic Rainforest, from north to south, have something in common: the heavy rainfall caused by the proximity of the ocean and the winds that blow inward over the continent. These winds carry masses of very moist air, and when these come up against the mountains of the Atlantic Rainforest, they condense and form rain.

Golden lion tamarin(6)

Golden lion tamarin(6)

Reference:

PRADO, J. F. de Almeida. Pero Vaz de Caminha: carta do achamento do Brasil. Rio de Janeiro: Agir, 1998. (Coleção Nossos Clássicos, nº 87)

Images:

(1) Photo: Abrivio/Wikipedia

(2) Photo: Luis A. Florit

(3) Photo: Mauroguanandi/Wikipedia

(4) Photo: Helio VL/Wikipedia

(5) Photo: Martin St.Amant/Wikipedia

(6) Photo: su neko/Wikipedia

See also other Brazilian biomes:

The Amazon biome

The Pantanal biome

The Caatinga biome

Cerrado Biome

Southern Plains Biome

The Coastal Biome

Sources:

Ibama

IB/USP

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

Consultancy:

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

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