The Atlantic Forest, also called Mata Atlântica in Portuguese, is a wet forest with many leafy trees. It runs along the Atlantic coast of Brazil, from the northeast state of Rio Grande do Norte to the southern state of Rio Grande do Sul. It also reaches inland to Paraguay and the Misiones Province of Argentina, where it is known as the Missionary rainforest in Spanish, called Selva Misionera.

The Atlantic Forest includes different areas within several types of environments: seasonal wet and dry tropical forests, tropical and subtropical grasslands, savannas, shrublands, and mangrove forests. This region is known for having many different plant and animal species, many of which are found only there.

Over 500 years ago, the Portuguese colonists first saw this forest. At that time, it was thought to cover between 1,000,000 and 1,500,000 square kilometers, stretching far inland. This made it the second largest rainforest on Earth, after the Amazon rainforest. However, more than 85% of the original forest has been cut down, putting many plant and animal species at risk of disappearing.

Ecology

The Atlantic Forest region includes several types of forests, each with unique features:

Restinga forests grow on coastal dunes that have settled over time. These forests are usually dense with short trees. Open restinga is a different type, resembling a savanna with scattered small trees, shrubs, and a thick layer of grasses and herbs.

Seasonal tropical moist forests receive more than 2,000 mm (79 in) of rain each year. These include Tropical Moist Lowland Forests, Submontane Forests, and Montane Forests.

Tabuleiro forests are found on very wet clay soils, while Tabuleiro Savannas grow on sandier soils that drain water more quickly. These areas depend on moisture from the ocean.

Further inland are the Atlantic dry forests, which act as a transition between the dry Caatinga to the northeast and the Cerrado savannas to the east. These forests are shorter and more open, with many trees that lose their leaves seasonally. They have less variety of plants compared to tropical moist forests. These forests receive 700 to 1,600 mm of rain each year, with a clear dry season. This group includes Deciduous and Seasonal Semideciduous Forests, each with lowland and mountain regions.

Montane forests are found at higher elevations on mountains and plateaus in southern Brazil. These are also called Araucaria moist forests.

Mussununga forests are located in southern Bahia and northern Espírito Santo states. This ecosystem ranges from grasslands to woodlands growing on sandy soils. The name "Mussununga" comes from the Tupi-Guarani language and means "soft and wet white sand."

Shrubby montane savannas are found at the highest elevations and are also called Campo rupestre.

The Atlantic Forest is unique because it includes a true tropical rainforest as far south as 28°S latitude. This happens because trade winds bring rain during the southern winter. For example, the northern Zona da Mata region in northeastern Brazil gets more rain between May and August than during the summer. The geographic range of the Atlantic Forest varies depending on the source. In 2018, information about the four most important boundaries and their overlaps was reviewed.

Geography

The Atlantic Forest covers most of the eastern part of Brazil (92% of the total area), and also covers parts of eastern Paraguay (6%) and northeastern Argentina (2%).

History

The Atlantic Forest has changed a lot over the past two time periods. Human activity and environmental changes were important reasons for these changes.

During cold periods in the Pleistocene, the Atlantic Forest became much smaller and was limited to small, protected areas in deep valleys. These areas were separated by dry forests or desert-like regions called caatingas. Humans first came into contact with the Atlantic Forest about 18,000 years ago during the Late Pleistocene. The forest looked very different in the Pleistocene compared to today. Vegetation included some heavy rainforests and many dry grasslands and forests.

Early human hunting likely caused the first large-scale loss of big mammals in the region. During the Holocene, Indigenous groups used slash-and-burn farming, which changed natural paths for animals and plants into areas for growing food. Changes in the landscape and animal populations led to more ecological changes during the Holocene. This time was marked by the growth of dense rainforests.

Unlike refuges for equatorial rainforests, the safe areas for the Atlantic Forest were not identified in detail.

By around 1500 CE, when Europeans arrived, the Atlantic Forest covered about 1,300,000 km² (500,000 mi²). The land Europeans first saw was not untouched nature. Researchers believe that Indigenous people shaped 60–80% of the forest’s landscape before European arrival. Portuguese colonists used Indigenous labor and knowledge to harvest Paubrasilia echinata, a tree that produced red dye from its trunk. Portuguese sugar plantations, called engenhos, had the greatest impact on the Atlantic Forest during colonial times. Colonists cleared forests to create space for sugar plantations and to fuel mills for processing sugar. Over time, these actions changed the forest in ways that did not happen under Indigenous management.

The Atlantic Forest became fragmented after early colonial activities. Forest fragmentation continues to affect the region and modern conservation efforts.

The endangered golden lion tamarin drew global attention to the Atlantic Forest in 1970.

Biodiversity

Although only 28% of the original plant cover remains, the Atlantic Forest is very rich in biodiversity and has many species found only in this area. About 40% of its vascular plants and up to 60% of its vertebrates are endemic, meaning they exist nowhere else on Earth. Brazil’s official list of threatened species includes more than 140 land mammal species found in the Atlantic Forest. In Paraguay, the Atlantic Forest has suffered major damage in recent years. Paraguay has 35 species listed as threatened, and 22 species are threatened in the interior part of the Atlantic Forest in Argentina. Nearly 250 species of amphibians, birds, and mammals have gone extinct due to human activity over the past 400 years. Today, over 11,000 species of plants and animals are considered threatened in the Atlantic Forest. More than 52% of tree species and 92% of amphibians are found only in this region. The forest is home to about 20,000 plant species, with nearly 450 tree species growing in just one hectare in some areas.

The Atlantic Forest is one of the most studied tropical ecosystems. For example, over 3,000 tree species, 98 bat species, 94 large or medium-sized mammal species, more than 2,000 epiphyte species, 26 primate species, 528 amphibian species, 124 small mammal species, and over 800 bird species have been recorded there.

New species are still being discovered in the Atlantic Forest. Between 1990 and 2006, over 1,000 new flowering plants were found. In 1990, scientists found a small group of black-faced lion tamarins (Leontopithecus caissara), which had been thought to be extinct. In 1991, the butterfly Actinote zikani was rediscovered in southern Brazil after being declared extinct 10 years earlier. A new species of blonde capuchin (Cebus queirozi), named for its bright blonde hair, was discovered in northeastern Brazil at the Pernambuco Endemism Center in 2006. The maned sloth (Bradypus torquatus), an endangered three-toed sloth named for its long hair, is found only in the Atlantic Forest. The Hylid tree frog Dendropsophus branneri is also found only in this region.

Conservation

The needs of modern human societies for forest resources have greatly reduced the size of the Atlantic Forest, leading to a loss of species. Nearly 88% of the original forest has been lost and replaced by human-modified areas such as pastures, farmland, and cities. This deforestation continues at an annual rate of 0.5% and up to 2.9% in urban areas.

Habitat fragmentation causes a series of changes to the original forest landscape. For example, human activities, such as destroying habitats, have caused an extinction crisis in the Atlantic Forest. Species that are found only in this region are especially at risk of extinction because they live in small areas and are not common. A study of forest fragments showed that areas smaller than 25 hectares had only 60% of the original plant biomass. Ecological processes like seed dispersal, the movement of genes between populations, and the spread of species are disrupted by fragmentation. Many important animals that help spread seeds have gone extinct, which may lead to the extinction of tree species that rely on these animals for reproduction. With species already in danger, continued deforestation is expected to cause more extinctions.

Because the Atlantic Forest is home to many unique plants and animals, and because fragmentation threatens these species, groups and organizations are working to restore the ecosystem. Non-governmental organizations (NGOs) in Brazil help by providing money and professional support through the Brazilian Environmental Movement. One group, BirdLife International, uses research to protect bird species and teach people about using natural resources in ways that are sustainable.

Some organizations receive funding from the Critical Ecosystem Partnership Fund if they follow its rules. These rules include programs like the Species Protection Program, the Program for Supporting Private Natural Heritage Reserves, and the Institutional Strengthening Program.

Another way to protect biodiversity in the Atlantic Forest is by creating wildlife corridors. The World Bank is giving $44 million to build a corridor called the Central Biodiversity Corridor in the Atlantic Forest and another in the Amazon. The Brazilian Development Bank has provided non-repayable loans to fund 16 to 18 restoration projects covering 3,500 hectares and costing about $22 million under the Iniciativa BNDES Mata Atlântica. To preserve diversity, the state of São Paulo created the Restinga de Bertioga State Park, a 9,300-hectare area that also acts as a wildlife corridor connecting coastal regions to the Serra do Mar mountain range. Some groups, like the Nature Conservancy, plan to restore lost forest areas and build corridors that work with the lifestyles of local people. The Amazon Institute is helping to replant forests in northeastern Brazil’s Pernambuco state. In 2007, Joao Milanez and Joanne Stanulonis planted 5,500 trees in the Gravata mountains, adding to the remaining ancient forest.

The Pact for Atlantic Forest Restoration has brought together over 100 businesses, NGOs, and government groups to restore 15 million hectares of the original ecosystem by 2050.

The Pontifícia Universidade Católica do Rio Grande do Sul maintains a private reserve of about 3,100 hectares in the Araucaria moist forest ecoregion, near São Francisco de Paula in Rio Grande do Sul. This reserve is used for research and protecting biodiversity.

Ecoregions

The Atlantic Forest Biome includes the following land regions:

• Alto Paraná Atlantic forests
• Araucaria moist forests
• Atlantic Coast restingas
• Bahia coastal forests
• Bahia interior forests
• Caatinga moist forests
• Pernambuco coastal forests
• Pernambuco interior forests
• Serra do Mar coastal forests

• Atlantic dry forests

• Campos rupestres

• Bahia mangroves
• Ilha Grande mangroves
• Rio Piranhas mangroves
• Rio São Francisco mangroves