Wikipedia Deep Dive

Atlantic Forest

13 min read

When Portuguese sailors first glimpsed the coast of Brazil in 1500, they encountered a wall of green stretching as far as the eye could see. This forest seemed endless, running along the entire Atlantic seaboard and disappearing inland toward the unknown interior. At that time, the Atlantic Forest covered somewhere between one million and one and a half million square kilometers, making it the second largest rainforest on Earth after the Amazon.

Today, less than fifteen percent of that forest remains.

A Forest Like No Other

The Atlantic Forest, known in Portuguese as the Mata Atlântica, is not a single uniform ecosystem but rather a complex tapestry of different forest types. It stretches from Rio Grande do Norte in northeastern Brazil all the way down to Rio Grande do Sul in the south, a distance of roughly 4,000 kilometers. The forest also reaches inland into Paraguay and the Misiones Province of Argentina, where locals call it the Selva Misionera, or Missionary Rainforest.

What makes this forest biologically remarkable is its extraordinary diversity. Approximately forty percent of its vascular plants exist nowhere else on Earth. For vertebrates, that number climbs even higher, with up to sixty percent of species being endemic to this region alone. In some locations, scientists have counted nearly 450 different tree species within a single hectare, an area roughly the size of two American football fields.

To put this in perspective, the entire British Isles contains about 35 native tree species.

The Atlantic Forest breaks the rules of where tropical rainforests are supposed to exist. Most tropical rainforests cluster near the equator, but this one extends as a true rainforest all the way to 28 degrees south latitude, roughly equivalent to the position of Brisbane in Australia or Durban in South Africa. The reason lies in the trade winds, which carry moisture from the Atlantic Ocean and dump it along the coast even during the southern winter. The northern part of the forest, in a region called the Zona da Mata, actually receives more rain between May and August than during the summer months.

The Many Faces of the Forest

The Atlantic Forest encompasses an astonishing variety of ecosystems, each adapted to different conditions of soil, elevation, and rainfall.

Along the coast, you find the restinga forests, which grow on ancient sand dunes that have stabilized over millennia. These forests can be dense and closed, or they can open up into savanna-like formations with scattered clumps of small trees and shrubs amid grasslands. The word restinga comes from Portuguese and originally referred to narrow strips of coastal land.

Moving inland and upward, seasonal tropical moist forests receive more than 2,000 millimeters of rain annually, nearly twice what London gets in a typical year. These forests transition through lowland, submontane, and montane zones as elevation increases. The tabuleiro forests grow over clay soils that retain moisture, while their neighboring savannas occupy sandier ground that drains more quickly. Both depend on water vapor carried inland from the ocean.

Further from the coast, the character of the forest changes dramatically. The Atlantic dry forests form a transitional zone between the humid coastal areas and two very different ecosystems, the Caatinga to the northeast and the Cerrado to the east. The Caatinga is a semi-arid region dominated by thorny scrubland, while the Cerrado is a vast tropical savanna. The dry forests stand shorter and more open than their coastal counterparts, with many deciduous trees that drop their leaves during distinct dry seasons. Annual rainfall here ranges from 700 to 1,600 millimeters.

At higher elevations across the mountains and plateaus of southern Brazil, the Araucaria moist forests dominate. These forests take their name from the Araucaria angustifolia, the Paraná pine, a dramatic tree with an umbrella-shaped crown that can live for over 500 years. Despite its common name, it is not actually a pine but belongs to an ancient family of conifers that dates back to the age of dinosaurs.

In southern Bahia and northern Espírito Santo states, you find the Mussununga forests. The name comes from the Tupi-Guarani language of Indigenous peoples and means soft and wet white sand. These ecosystems range from open grasslands to closed woodlands, all growing on sandy soils called spodosols, which are typically found in much colder climates.

At the very highest elevations, the forest gives way to shrubby montane savannas called campo rupestre, literally meaning rocky field. These windswept highlands support specialized plants adapted to thin soils, intense sunlight, and dramatic temperature swings between day and night.

Deep Time and Human History

The Atlantic Forest has not always looked the way it does today, or rather, the way it did five centuries ago. During the ice ages of the Pleistocene epoch, which ended about 11,700 years ago, the forest repeatedly contracted into small refugia, areas where conditions remained favorable while the surrounding landscape turned to dry forest or semi-desert. These refugia occupied sheltered gullies and valleys, isolated islands of moisture in an increasingly arid world.

Humans first entered this changing landscape about 18,000 years ago, toward the end of the last ice age. The forest they encountered looked nothing like the lush rainforest that later Portuguese colonizers would see. Instead, they found a mosaic of vegetation ranging from scattered rain-heavy forests to extensive dry grasslands.

These early inhabitants left their mark. Their hunting likely drove the first mass extinctions of large mammals in the region. As the climate warmed and the Holocene epoch began, Indigenous groups developed slash-and-burn agriculture, clearing patches of forest to create gardens. Over thousands of years, this practice transformed the landscape, creating what ecologists call biological corridors and converting wild forest into managed food production zones.

By the time Portuguese ships arrived in 1500, researchers estimate that Indigenous land management had shaped between sixty and eighty percent of the forest landscape. The forest that the colonizers encountered was not pristine wilderness but rather a landscape that had been cultivated, managed, and transformed by human hands for millennia.

Colonial Destruction

The Portuguese wasted no time exploiting their new territory. They quickly learned from Indigenous peoples about Paubrasilia echinata, a tree that produced a valuable red dye from its trunk. This tree gave Brazil its name, from the Portuguese word brasa meaning ember, referring to the wood's reddish color. For the first few decades of colonization, extracting this brazilwood was the primary economic activity.

But the real devastation came with sugar.

Portuguese colonists established sugar plantations called engenhos along the coast, and these operations required clearing vast swaths of forest. The trees fell not only to make room for sugarcane fields but also to fuel the mill furnaces that converted raw cane into exportable sugar. Each mill consumed enormous quantities of firewood, and when the nearby forests were exhausted, the operations simply moved to new areas and started again.

This pattern of destruction, clear the forest, exhaust the land, move on, became the template for Brazilian agriculture for centuries. The sugar economy transformed the Atlantic Forest region in ways that thousands of years of Indigenous land management never had.

The Crisis Today

The numbers are stark. Almost eighty-eight percent of the original forest has been converted to pastures, croplands, and urban areas. Deforestation continues at an annual rate of about half a percent, with rates climbing as high as nearly three percent near expanding cities. What remains is not a continuous forest but a patchwork of isolated fragments, some tiny, some large, but all separated from each other by human-dominated landscapes.

This fragmentation creates a cascade of ecological problems far worse than the simple loss of area would suggest. Small forest patches cannot support large animals with extensive home ranges. Seed dispersers like monkeys and large birds disappear from fragments too small to sustain their populations, and without these animals spreading seeds, many tree species cannot reproduce. Gene flow between populations stops when animals cannot travel between fragments, leading to inbreeding and reduced genetic diversity.

Edge effects compound the damage. The boundary between forest and cleared land creates a harsh transition zone where temperature, humidity, and wind exposure differ dramatically from the forest interior. In small fragments, these edge effects can penetrate so deeply that no true interior forest conditions remain at all.

A study of Atlantic Forest fragments found that community-level biomass, essentially the total weight of living organisms, dropped to just sixty percent in plots smaller than 25 hectares. The fragments were losing not just species but the basic biological substance of the ecosystem.

Nearly 250 species of amphibians, birds, and mammals have gone extinct in the Atlantic Forest over the past 400 years as a direct result of human activity. Over 11,000 species of plants and animals are currently considered threatened. The official Brazilian list of threatened terrestrial mammals includes over 140 species found in the Atlantic Forest. In Paraguay, 35 species are listed as threatened; in the Argentine portion of the forest, 22 species face extinction.

A Hotspot of Discovery

Despite the destruction, or perhaps because scientists know their time is limited, the Atlantic Forest remains one of the most intensively studied tropical ecosystems on Earth. Researchers have documented over 3,000 tree species, nearly 100 bat species, 94 large or medium-sized mammal species, more than 2,000 species of epiphytes, those plants that grow on other plants, 26 primate species, 528 amphibian species, 124 small mammal species, and over 800 bird species.

And they keep finding more.

Between 1990 and 2006 alone, scientists discovered over a thousand new flowering plant species in the Atlantic Forest. Some discoveries have been rediscoveries, species thought extinct turning up in isolated fragments. In 1990, researchers found a small population of the black-faced lion tamarin, a species that had been written off as gone forever. The following year, the butterfly Actinote zikani reappeared in southern Brazil, a decade after being declared extinct.

In 2006, scientists announced the discovery of a new primate species, the blonde capuchin, named for its striking golden hair. This monkey was found at the Pernambuco Endemism Center, a region in northeastern Brazil known for its unique species assemblages. The fact that a new primate could be found in the twenty-first century, in a forest that had been studied for decades, speaks to how much remains unknown.

The maned sloth represents another Atlantic Forest endemic. This three-toed sloth species, distinguished by the long black hair around its head and neck that gives it a somewhat leonine appearance, exists nowhere else on Earth. If the Atlantic Forest disappears, so does the maned sloth.

The Golden Lion Tamarin Effect

In 1970, the plight of the golden lion tamarin captured international attention and sparked global interest in conserving the Atlantic Forest. This small monkey, barely larger than a squirrel and covered in brilliant orange-gold fur, had become vanishingly rare. Its story galvanized conservation efforts and helped shift public perception of the forest from an obstacle to development into a treasure worth protecting.

Today, numerous organizations work to preserve and restore what remains of the Atlantic Forest. BirdLife International focuses on protecting the forest's avian biodiversity while promoting sustainable resource use among local communities. The Critical Ecosystem Partnership Fund provides grants to organizations meeting specific conservation criteria, supporting programs focused on species protection, private natural heritage reserves, and institutional strengthening.

One promising strategy involves creating wildlife corridors to reconnect isolated forest fragments. The World Bank has contributed 44 million dollars to establish the Central Biodiversity Corridor in the Atlantic Forest, along with a companion corridor in the Amazon. These corridors allow animals to move between fragments, enabling gene flow, recolonization of areas where populations have gone locally extinct, and escape from disturbances like fires or disease outbreaks.

The Brazilian Development Bank has financed 16 to 18 ecosystem restoration projects totaling 3,500 hectares through its Iniciativa BNDES Mata Atlântica program, with approximately 22 million dollars in non-reimbursable loans. The state of São Paulo created the Restinga de Bertioga State Park, covering 9,300 hectares and serving as a wildlife corridor connecting coastal regions to the Serra do Mar mountain range.

Smaller efforts matter too. In 2007, Joao Milanez and Joanne Stanulonis planted 5,500 trees in the mountains near Gravatá in the northeastern state of Pernambuco, working with the Amazon Institute to add to the precious remnants of ancient forest in the region.

Perhaps the most ambitious initiative is the Pact for Atlantic Forest Restoration, which has assembled over 100 businesses along with governmental and non-governmental organizations around a shared goal: restoring 15 million hectares of the original ecosystem by 2050. For context, 15 million hectares is roughly the size of Nepal.

What Remains

The Atlantic Forest today contains twenty-eight percent of its original native vegetation cover, a number that sounds catastrophic but also represents something remarkable. Despite five centuries of exploitation, this forest retains extraordinary biodiversity. Over half of its tree species exist nowhere else on Earth. Ninety-two percent of its amphibians are endemic. New species continue to be discovered, and species thought extinct keep turning up in unexpected places.

The forest spans multiple political jurisdictions, with ninety-two percent in Brazil, six percent in Paraguay, and two percent in Argentina. Each country faces its own challenges in balancing development pressures with conservation needs. In Brazil, the forest runs through some of the country's most densely populated regions, including the megalopolises of São Paulo and Rio de Janeiro. Every hectare preserved represents land that could otherwise be converted to farms, pastures, or suburbs.

Universities have become conservation partners. The Pontifícia Universidade Católica do Rio Grande do Sul maintains a private reserve of approximately 3,100 hectares called Pró-Mata near the city of São Francisco de Paula. This reserve protects Araucaria moist forest and serves as a living laboratory for research and biodiversity conservation.

The story of the Atlantic Forest is ultimately a story about choices. For five centuries, the choice was clear: the forest was a resource to be extracted and an obstacle to be cleared. Today, that calculus is shifting. The forest is increasingly understood not just as a collection of trees but as an irreplaceable library of biodiversity, a climate regulation system, a water purifier, and a source of as-yet-undiscovered medicines and materials.

Whether fifteen percent becomes ten percent or twenty percent depends on decisions being made right now, by governments, corporations, farmers, and ordinary citizens across three countries. The golden lion tamarin survived its brush with extinction. The black-faced lion tamarin emerged from the presumed dead. The question is whether we can extend that same reprieve to the thousands of other species that call this ancient, battered, resilient forest home.