The Atlantic Forest has been the backdrop for Brazil’s principal economic cycles over the past 500 years. Since colonization by the Portuguese, the region has seen long periods of intensive, unregulated use focused on extraction or agricultural production for export. Such is the case for the exploitation of Brazil wood and sugarcane, which have played a role in the occupation of the forested region of the Northeast. Over the centuries, the region has experienced gold and coffee cycles, urban expansion into the forest beginning in the 1920s and, more recently, illegal logging, hunting and capturing of animals, and extraction of plants such as the juçara palm (Euterpe edulis), a food source for several bird species. All of these processes have transformed the landscape of the ecosystem. But those who attended the lectures at the BIOTA-FAPESP Education Conference Cycle on August 22, 2013, saw that the remains of the Atlantic Forest still host a large diversity of plant and animal species despite such degradation.
“Among the approximately 5,000 plant varieties found only in the Atlantic Forest, bromeliads, orchids and palms are the most abundant,” said botanist Carlos Alfredo Joly of the Institute of Biology at the University of Campinas (Unicamp). Joly, coordinator of the BIOTA-FAPESP program, was speaking to an audience filled with high school students from São Paulo. Joly says that at the time the Portuguese arrived, the Atlantic Forest was the second-largest tropical forest in South America. It stretched for slightly more than 1.3 million square kilometers (km²), or 15% of Brazil’s national territory, along its coastline and inland through the states of Minas Gerais, São Paulo and Paraná, encompassing parts of what are now 17 states. Today, however, only 7% (95,000 km²) of its original coverage area remains, with the highest rates of deforestation occurring in the Northeastern states, where the remaining areas constitute no more than 2%. Owing to its large expanse, the Atlantic domain has different types of environments, with vegetation characteristic of dunes, restingas and mangroves, as well as forests of araucária, or Brazilian pine, and denser, moist montane (hillside) forests. There are also small enclaves near other ecosystems, such as the campo grasslands of the Pampa and the flat plains of the Pantanal wetland (see Pesquisa FAPESP Issue No. 207).
Among the species inhabiting these environments, dune and mangrove vegetation faces the most adverse environmental conditions, due in part to the high salinity and instability of the soil in which it grows. “Few species survive in this type of environment,” Joly says. “Mangrove areas, for example, are flooded with seawater that has a high saline content. So these plant species have developed specific adaptive mechanisms to survive under such conditions.” He says that mangrove groves throughout the world are characterized by only three tree genera: Rhizophora, Avicennia and Laguncularia. This hostile environment for trees is home to hundreds of species of fish and crustaceans, so its degradation has resulted in a loss of $1.6 billion per year, according to the United Nations Environment Program.
The remaining fragments of Atlantic Forest are important in the formation of rivers and waterfalls, which supply water to the 125 million people currently living in the Atlantic domain. “We’re talking about an environmental service of the highest importance for humans,” Joly says. The population density in these areas has rapidly increased in recent years, giving rise to a new problem of concern to the public. The soil of the Atlantic Forest is acid, sandy and nutrient-poor, in addition to being shallow and rather unstable. It is precisely that set of characteristics, aggravated by the occupation of slopes and foothills, that have led to landslides such as the one that occurred in the mountainous region of the state of Rio de Janeiro in 2011, killing more than 900 people.
The high degree of endemism among plant species extends to the fauna of the Atlantic Forest as well. According to biologist André Freitas, also of Unicamp’s Institute of Biology, 45% of the butterfly species in the Atlantic Forest are exclusive to that ecosystem. He explains that this biological diversity originated when fauna began to diversify thousands of years ago, by way of very different migratory routes. “There is a clear north-south dividing line with respect to the origin of this diversity,” he says. From the northern half of the state of Espírito Santo to the edges of the Atlantic Forest in the Northeast, the fauna abound with Amazonian features. Farther to the south, those features are more associated with species of the Andean range.” This division occurred in the Miocene epoch 23 million years ago, when the Nazca tectonic plate in the Pacific collided with the South American continental plate, pushing up the chain of Andes mountains that stretch from Chile to Venezuela and reach a height of nearly 3,500 meters.
The emergence of this enormous wall completely changed the biogeography of the region. Before it rose up, the rivers that now form the Amazon Basin flowed toward the Pacific Ocean. The mountains interrupted their path, however, and led to the formation of the present-day basin, whose waters drain off into the Atlantic Ocean. During that time, periodic climate changes created natural corridors of cold, moist forest that enabled Andean species to migrate to the Atlantic Forest. “When they arrived there, these species began to diversify,” Freitas says. One example is Leptanilloides atlantica, a recently-described ant species of the Serra do Mar mountain range. This genus of ants had been known only in the Andes region and Central America. The butterfly species Hyalenna pascua is the sole Atlantic Forest representative of an Andean genus. “These animals are from high mountains with a cold climate, and for this reason they did not come to the northern part of the Atlantic Forest.”
The ones that made it to that part of the Atlantic Forest were the Amazonian species, when the forest in the Northeast was connected to the Amazonian vegetation of the Guianas and the state of Pará near Marajó Island, as well as the areas around the Xingu, Tocantins and Araguaia rivers (see Pesquisa FAPESP Issue No. 210). One result of that connection is the Silvery-breasted Tanager (Tangara velia cyanomelaena)—a bird residing in the Atlantic Forest whose closest relative is the Opal-rumped Tanager (Tangara velia iridina) of the Amazon—in addition to several species of butterflies, beetles, lizards and amphibians.
Past climate changes also play an important role in that history, inasmuch as they caused the size of the forest to expand or diminish during certain periods. We know that continued maintenance of the Atlantic Forests depends on certain climate and soil conditions. “But in the past, when the climate was cold and much of the forest was drier, the size of the forest may possibly have been reduced to a few areas, where the minimum requirements for maintaining it remained intact,” Freitas says. At that time these forests were isolated, which encouraged the process of regional differentiation among species of the same genus. These regions are known as centers of endemism. There are three major centers in the Atlantic Forest, located in the states of Pernambuco, Bahia and Rio de Janeiro. In addition, there are two secondary centers, one in Santa Catarina and the other in central Brazil, known as Araguaia. “For many groups of animals typical of moist forests, the differentiation between populations in the centers of endemism of the Atlantic ecosystem is quite clear, and this confirms a historical process of regional differentiation in the past.”
One very well-known case that attests to the existence of these centers of endemism involves lion tamarins (Leontopithecus). There are four species of these animals in the Atlantic Forest, one in each of its centers of endemism, and each has a different color pattern. “The large diversification and high degree of endemism of Atlantic Forest fauna can be explained by a combination of different processes.” So, Freitas concludes, the great biodiversity found throughout this environment is the result of interaction between the environmental tolerances of the different animal groups; heterogeneity of habitats, such as forests, restingas and campos; and historical processes such as climate change.
What’s left to preserve?
The fact that the Atlantic Forest is significantly degraded yet still harbors many endemic species has led to its inclusion on the map of the world’s biodiversity hotspots: areas that have lost at least 70% of their original vegetation coverage but, when combined, are home to over 60% of all terrestrial species on the planet. Today these regions occupy 2% of the land surface and host a population of over 1.1 billion people. Many of the economic activities in these areas rely on products from healthy ecosystems, derived through the exploitation of wild plants and animals. In Joly’s opinion, these factors make the Atlantic Forest a high-priority area for conservation.
But that is not what has happened. In June, the SOS Atlantic Forest Foundation and the Brazilian National Institute for Space Research (INPE) released the latest version of the Atlas of Remaining Forest Areas of the Atlantic Forest. Joly says that after a three-year decline, the rate of deforestation in the Atlantic Forest picked up pace again in 2011 and 2012, reaching its highest level since 2008. According to INPE researcher Flávio Jorge Ponzoni, one of the invited speakers, the increase in 2012 was led by Minas Gerais State, which was responsible for half the deforestation in that period. Ponzoni helped prepare the Atlas and explained that the monitoring includes areas up to three hectares in size, or about three football fields. “Everything is done through visual interpretation of satellite images. It’s a subjective analysis. So to ensure that the data are comparable, we update the database every year.” It was the fourth consecutive year that Minas Gerais ranked first in deforestation. That led SOS Atlantic Forest to file a complaint with the Minas Gerais Office of the Prosecutor for the Public Interest, which responded in kind. “It was impressive how quickly the authorities mobilized,” Ponzoni comments.
Failure to preserve the Atlantic Forest could trigger another problem: we know that deforestation contributes to global warming. If temperatures continue to rise, the forest tends to return more carbon dioxide (CO2) into the atmosphere than before. “When we compare the Atlantic Forest to the Amazon Forest, we can see that there is an enormous difference in the amount of CO2 accumulated, whether in the trunks or branches of the trees, or in the soil,” Joly says. The same thing happens in regard to the amount of nitrogen (N) stored in the soil; it is likely to be released in greater amounts when warming occurs.
The outlook does not seem very promising. By 2100, 30% of the area now occupied by 60 species of trees in the Atlantic Forest is expected to be lost. “That projection is based on optimistic scenarios from the Intergovernmental Panel on Climate Change (IPCC), based on all members meeting the commitments they agreed to in the Kyoto Protocol and the global temperature not rising more than two degrees this century,” Joly warns. Under the worst-case scenario, in which the temperature rises as much as four degrees, the estimated loss of that same area could run as high as 65%.
The BIOTA-FAPESP Education Conference Cycle is an initiative of the BIOTA-FAPESP program in partnership with Pesquisa FAPESP, focused on discussing the challenges involved in preserving Brazil’s principal ecosystems. The lectures, to be presented between now and November, are intended to present knowledge created by researchers throughout Brazil, aimed at improving the quality of environmental and science education for high school teachers and students in Brazil.Republish