{"id":138448,"date":"2013-10-23T16:20:30","date_gmt":"2013-10-23T18:20:30","guid":{"rendered":"http:\/\/revistapesquisa.fapesp.br\/?p=138448"},"modified":"2015-09-21T18:20:30","modified_gmt":"2015-09-21T21:20:30","slug":"on-the-razors-edge","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/on-the-razors-edge\/","title":{"rendered":"On the razor\u2019s edge"},"content":{"rendered":"
\"View

ANDR\u00c9 FREITAS\/UNICAMP<\/span>View of mangrove vegetation in the Picinguaba conservation area in Ubatuba, S\u00e3o PauloANDR\u00c9 FREITAS\/UNICAMP<\/span><\/p><\/div>\n

The Atlantic Forest has been the backdrop for Brazil\u2019s 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 ju\u00e7ara palm (Euterpe edulis<\/i>), 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.<\/p>\n

\u201cAmong the approximately 5,000 plant varieties found only in the Atlantic Forest, bromeliads, orchids and palms are the most abundant,\u201d 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 S\u00e3o 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 (km\u00b2), or 15% of Brazil\u2019s national territory, along its coastline and inland through the states of Minas Gerais, S\u00e3o Paulo and Paran\u00e1, encompassing parts of what are now 17 states. Today, however, only 7% (95,000 km\u00b2) 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<\/i> and mangroves, as well as forests of arauc\u00e1ria, <\/i>or Brazilian pine, and denser, moist montane (hillside) forests. There are also small enclaves near other ecosystems, such as the campo<\/i> grasslands of the Pampa and the flat plains of the Pantanal wetland (see Pesquisa FAPESP Issue No. 207<\/i>)<\/a>.<\/p>\n

\"From

EDUARDO CESAR<\/span>From left, Fl\u00e1vio Ponzoni, Andr\u00e9 Freitas and Carlos Alfredo JolyEDUARDO CESAR<\/span><\/p><\/div>\n

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. \u201cFew species survive in this type of environment,\u201d Joly says. \u201cMangrove 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.\u201d He says that mangrove groves throughout the world are characterized by only three tree genera: Rhizophora<\/i>, Avicennia<\/i> and Laguncularia<\/i>. 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.<\/p>\n

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. \u201cWe\u2019re talking about an environmental service of the highest importance for humans,\u201d 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.<\/p>\n

\"\"<\/a>The high degree of endemism among plant species extends to the fauna of the Atlantic Forest as well. According to biologist Andr\u00e9 Freitas, also of Unicamp\u2019s 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. \u201cThere is a clear north-south dividing line with respect to the origin of this diversity,\u201d he says. From the northern half of the state of Esp\u00edrito 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.\u201d 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.<\/p>\n

Divided past
\n<\/b>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. \u201cWhen they arrived there, these species began to diversify,\u201d Freitas says. One example is Leptanilloides atlantica<\/i>, 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<\/i> is the sole Atlantic Forest representative of an Andean genus. \u201cThese 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.\u201d<\/p>\n

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 Par\u00e1 near Maraj\u00f3 Island, as well as the areas around the Xingu, Tocantins and Araguaia rivers (see Pesquisa FAPESP Issue No. 210<\/i><\/a>). One result of that connection is the Silvery-breasted Tanager (Tangara velia cyanomelaena<\/i>)\u2014a bird residing in the Atlantic Forest whose closest relative is the Opal-rumped Tanager (Tangara velia iridina<\/i>) <\/i>of the Amazon\u2014in addition to several species of butterflies, beetles, lizards and amphibians.<\/p>\n