The Atlantic Forest () is a moist broadleaf forest that extends along the Atlantic coast of Brazil from Rio Grande do Norte state in the northeast to Rio Grande do Sul state in the south and inland as far as Paraguay and the Misiones Province of Argentina, where it is known as the Missionary rainforest ().
The Atlantic Forest has ecoregions within the following biome categories: seasonal moist and dry broad-leaf tropical forests, tropical and subtropical grasslands, savannas, and shrublands, and mangrove forests. The Atlantic Forest is characterized by a high biodiversity and endemism.Dafonseca, G. 1985. The Vanishing Brazilian Atlantic Forest. Biological Conservation 34:17-34.
It was the first environment that the Portuguese colonists encountered over 500 years ago, when it was thought to have had an area of , and stretching an unknown distance inland, making it, back then, the second largest rainforest on the planet, only behind the Amazon rainforest.Por, Francis Dov. 1992. Sooretama: the Atlantic rain forest of Brazil. The Hague: SPB Academic Pub. Over 85% of the original area has been deforested, threatening many plant and animal species with extinction.
Ecology
The Atlantic Forest region includes forests of several variations: Restinga is a forest type that grows on stabilized coastal dunes. Restinga forests are generally closed canopy short forests with tree density. Open restinga is an open, savanna-like formation with scattered clumps of small trees and shrubs and an extensive layer of herbs, grasses, and sedges.Thomas, William Wayt, and Elizabeth G. Britton. 2008. The Atlantic coastal forest of Northeastern Brazil. Bronx, N.Y.: The New York Botanical Garden Press. Seasonal tropical moist forests may receive more than of rain a year. These include Tropical Moist: Lowland Forests, Submontane Forest, and Montane Forests. Tabuleiro forests are found over very moist clay soils and Tabuleiro Savannas occur over faster-draining sand soils. These are humid areas that rely on water vapor from the ocean.Galindo Leal, Carlos, and Ibsen de Gusmão Câmara. 2003. The Atlantic Forest of South America: biodiversity status, threats, and outlook. Washington: Island Press. Further inland are the Atlantic dry forests, which form a transition between the arid Caatinga to the northeast and the Cerrado savannas to the west. These forests are lower in stature; more open, with high abundance of deciduous trees and lower diversity when compared to tropical moist forests. These forests have between 700 and 1600 mm of precipitation annually with a distinct dry season. This includes Deciduous and Seasonal semideciduous forest each with their own lowland and montane regions. Montane forests are higher altitude wet forests across mountains and plateaus of southern Brazil. Also called Araucaria moist forests. The Mussununga forests occur in southern Bahia and northern Espírito Santo states. The Mussununga ecosystem ranges from grasslands to woodlands associated with sandy spodosols. The word Mussununga is Amerindian Tupi-Guarani meaning soft and wet white sand. Shrubby montane savannas occur at the highest elevations, also called Campo rupestre.
The Atlantic Forest is unusual in that it extends as a true tropical rain forest to latitudes as far as 28°S. This is because the trade winds produce precipitation throughout the southern winter. In fact, the northern Zona da Mata of northeastern Brazil receives much more rainfall between May and August than during the southern summer. The geographic range of Atlantic Forest vary depending on author or institution that published them. Information on four most important boundaries as well as their union and intersection was reviewed in 2018.
Geography
The Atlantic Forest mainly covers regions of eastern Brazil (92% of the total area), but also reaches eastern Paraguay (6%) and northeastern Argentina (2%).
History
The Atlantic Forest has undergone great changes across the last two epochs. Human interaction and environmental changes have been major factors in the ecological history of the forest region.
During glacial periods in the Pleistocene, the Atlantic Forest is known to have shrunk to extremely small fragmented refugia in highly sheltered gullies, being separated by areas of dry forest or semi-deserts known as caatingas. Humans first interacted with the Atlantic Forest 18,000 years ago during the Late Pleistocene. The Atlantic Forest region was very different in the Pleistocene than today. Vegetation ranged from a few rain-heavy forests to an abundance of dry open grasslands and forests.
Early human hunting likely resulted in the first mass extinctions of large mammals in the Atlantic Forest region. Indigenous groups in the Holocene used slash-and-burn agriculture which transformed biological corridors into food resources. Changes in landscape and faunal demographics contributed to greater ecological changes in the Holocene. Ecological changes in this era were signified by the increase in dense rainforests.
Unlike refugia for equatorial rainforests, the refuges for the Atlantic Forest have never been the product of detailed identification.
By the time of European colonization circa 1500 CE, the Atlantic Forest stretched approximately . The regions first encountered by Europeans were not pristine landscape. Researchers estimate that Indigenous land management shaped 60–80% of the forest landscape by the time of European contact. Portuguese colonists exploited Indigenous labor and knowledge to extract Paubrasilia echinata for the red dye the trunk of the plant could produce. Portuguese sugar plantations, engenho, had the most impact on the Atlantic Forest region in colonial times. Colonists needed forests cleared to both hold sugar plantations and to feed mill furnances for sugar conversion. Overtime, these interactions shaped the Atlantic Forest region in a manner that had not occurred under Indigenous land management.
The Atlantic Forest has become fragmented since early colonial interactions. Forest fragmentation continues to impact the Atlantic Forest region and contemporary conservation efforts.
The threatened existence of the golden lion tamarin sparked global interest in the Atlantic Forest in 1970.
Biodiversity
Despite having only 28% of native vegetation cover remaining, the Atlantic Forest remains extraordinarily lush in biodiversity and endemic species, many of which are threatened with extinction. Approximately 40 percent of its vascular plants and up to 60 percent of its vertebrates are endemic species, meaning they are found nowhere else in the world.Tabarelli, Marcelo, Antonio Venceslau Aguiar, Milton Cezar Ribeiro, Jean Paul Metzger, and Carlos A. Peres. "Prospects for Biodiversity Conservation in the Atlantic Forest: Lessons from Aging Human-modified Landscapes." Biological Conservation 143.10 (2010): 2328-340. The official threatened species list of Brazil contains over 140 terrestrial mammal species found in Atlantic Forest. In Paraguay the Atlantic Forest has been heavily impacted in recent years.de la Sancha, Noé U., Sarah A. Boyle, and Nancy E. McIntyre. "Identifying structural connectivity priorities in eastern Paraguay's fragmented Atlantic Forest." Scientific reports 11, no. 1 (2021): 16129. https://doi.org/10.1038/s41598-021-95516-3 In Paraguay there are 35 species listed as threatened, and 22 species are listed as threatened in the interior portion of the Atlantic Forest of Argentina. Nearly 250 species of amphibians, birds, and mammals have become extinct due to the result of human activity in the past 400 years. Over 11,000 species of plants and animals are considered threatened today in the Atlantic Forest. Over 52% of the tree species and 92% of the amphibians are endemic to this area. The forest harbors around 20,000 species of plants, with almost 450 tree species being found in just one hectare in some locations.World Wildlife Fund: Atlantic Forest . World Wildlife Fund. 29 November 2011.
The Atlantic Forest is one of the best studied tropical ecosystems. For example, over 3000 tree species, 98 bat species, 94 large or medium-sized mammal species, over 2000 epiphyte species, 26 primate species, 528 amphibian species, 124 small mammal species, and over 800 bird species have been recorded in the Atlantic Forest.
New species are continually being found in the Atlantic Forest. In fact, between 1990 and 2006 over a thousand new flowering plants were discovered. Furthermore, in 1990 researchers re-discovered a small population of the black-faced lion tamarin (Leontopithecus caissara), previously thought to have been extinct.Reaka-Kudla, Marjorie L, Don E. Wilson, and Edward O. Wilson. Biodiversity II: Understanding and Protecting Our Biological Resources. Washington, D.C.: Joseph Henry Press, 1997. In 1991, the butterfly Actinote zikani was rediscovered in southern Brazil, after being declared extinct ten years earlier. A new species of blonde capuchin (Cebus queirozi), named for its distinguishing bright blonde hair, was discovered in northeastern Brazil at the Pernambuco Endemism Center in 2006.Pontes, A., A. Malta, and P. Asfora. 2006. A new species of capuchin monkey, genus Cebus erxleben (Cebidae, Primates): found at the very brink of extinction in the Pernambuco Endemism Centre. Zootaxa:1-12. A species of endangered three-toed sloth, named the maned sloth (Bradypus torquatus) because of its long hair, is endemic to the Atlantic Forest.Cassano, C., M. Kierulff, and A. Chiarello. 2011. The cacao agroforests of the Brazilian Atlantic forest as habitat for the endangered maned sloth Bradypus torquatus. Mammalian Biology 76:243-250. Hylid tree frog Dendropsophus branneri is also endemic to the Atlantic Forest.
Conservation Human impact
The incorporation of modern human societies and their needs for forest resources has greatly reduced the size of the Atlantic Forest, which has resulted in species impoverishment. Almost 88% of the original forest habitat has been lost and replaced by human-modified landscapes including pastures, croplands, and urban areas. This deforestation continues at an annual rate of 0.5% and up to 2.9% in urban areas. Agriculture: A major portion of human land use in the Atlantic Rain Forest is for agriculture. Crops include sugar-cane, coffee, tea, tobacco and more recently soybean and biofuel crops. Pasture: Even more common than using land for agriculture is the conversion of forest to cattle pastures. This is commonly done by slash and burn, which increases the likelihood of additional forest loss to human-induced wildfires. Hunting: Species in a fragmented forest are more susceptible to decline in population size because they are in a confined area that is more accessible to hunters. Larger animals make up the highest percentage of biomass. These animals are also the most rewarding to hunters and are heavily hunted in accessible fragments. This results in a change in species interactions such as seed dispersal and competition for resources. Logging: Logging removes 10 to 80% of the canopy cover of a forest, making that habitat more susceptible to natural elements such as wind and sunlight. This causes an increase in forest heating and desiccation.Laurance, William F., and Diana C. Useche. "Environmental Synergisms and Extinctions of Tropical Species." Conservation Biology 23.6 (2009): 1427–1437. Large amounts of organic litter and debris build up, which results in an increase in forest vulnerability to fires. Additionally, logging roads create accessibility for humans, thereby increasing the rate of human land disturbance and decreasing the amount of natural forest.