Location and General Description
This forest-dominated ecoregion is surrounded by open vegetation of Caatinga (north and east) and Cerrado (west and south) and is partially isolated from the main core of the Atlantic forest complex of ecoregions. Located mostly along the pediplained depression on River São Francisco, Atlantic dry forests cover an extensive area on eutrophic soils derived from limestone rocks of the Bambuí group (Andrade-Lima 1975 and 1981). The climate is mostly tropical with five dry months. Annual rainfall ranges from 850 to 1,000 mm. The relief is flat with some relict hills dispersed in the landscape. Tropical dry forests, deciduous or semi-deciduous, are the dominant vegetation type. Small patches of cerrado and caatinga are also found where soils and geomorphology are adequate. Dry forests are fairly dense, up to 25 to 30 m high and characterized by tree species such as Cavanillesia arborea, Cedrela fissilis, Schinopsis brasiliensis, Astronium urundeuva, Aspidosperma macrocarpa, and Tabebuia sp. (Ratter et al. 1978; Andrade-Lima 1981) The most remarkable tree is certainly Cavanillesia arborea, with a huge, bottle-shaped trunk that reaches its maximum diameter of 1.5 m or more about 3 m above ground level. It attains heights of about 27 m (Ratter et al. 1978). Associated with dry forests, there are several calcareous caves that harbor a unique and specialized biota (Mauro et al. 1982). A combination of geomorphological, geological, climatic, hydrological and vegetation features helps to delineate this ecoregion.
Although the biodiversity of Atlantic dry forests is still poorly-known, the presence of bird species restricted to them (Silva & Oren 1992, 1997; Raposo 1997) gives rise to predictions that endemic species for other biological groups will be found. Cave biota is believed to be very distinct, with spectacular adaptations and life history strategies. Because dry forests experience remarkable seasonal changes in structure, their biota should present interesting adaptations. Several bird species fly north during dry season, coming back to breed during wet season. Although this migratory system involves at least 20 species, little is known about it. Most of the endemic and semi-endemic species of vertebrates found in Atlantic dry forests are listed as threatened or near-threatened by IUCN and the Brazilian government. Wege & Long (1995) identified within Atlantic dry forests five key areas (Parnaguá and Corrente; Coribe; Palmas de Monte Alto; Itacarambi and Mocambinho; and Brejo do Amparo) that are important for conservation of six globally threatened birds (hyacinth macaw, Anodorhynchus hyacithinus; vinaceous amazon, Amazona vinacea; golden-capped parakeet, Aratinga auricapilla; moustached woodcreeper, Xiphocolaptes falcirostris; great xenops, Megaxenops paranaguae; and minas gerais tyrannulet, Phylloscartes roquettei).
Approximately 70 percent of the native forest has largely been destroyed. Because these forests grow on relatively rich soils, they are prime candidates for clearing both irrigated and dry-field agriculture (Silva & Oren 1997). Furthermore, the high biomass of these forests makes them important sources of fuel for Brazil's steel and pig iron industries, which run entirely on charcoal (Silva & Oren 1997). The most diverse dry forests on flat terrain and rich soil have been completely removed (Silva & Oren 1993).
Types and Severity of Threats
Currently, the few large remnants of dry forest are found only on the slopes of the plateaus bordering the São Francisco depression. Protected areas (Peruaçu and Serra das Confusões) are located on the extremes of the ecoregion, whereas its core region between Manga (Minas Gerais) and Ibotirama (Bahia) remains unprotected.
Justification of Ecoregion Delineation
These dry forests form the transitional habitat between the caatinga xeric shrublands and cerrado ecoregions of eastern Brazil Some authors (e.g., Andrade-Lima 1981) regard Atlantic dry forests as a kind of caatinga. Other botanical classifications ranked Atlantic dry forests as a distinct vegetation types (IBGE 1993). A large patch of dry forests closely related to Atlantic dry forests is found within the cerrado ecoregion, along the river Paranã depression (Silva, 1989). The linework for these patches and strips of dry forest follow the IBGE (1993) classifications of "montane seasonal deciduous forest", "submontane seasonal deciduous forest", "submontane seasonal semideciduous forest", and all subsequent "secondary vegetation and agricultural activities" enclosed or bordering on these forest types. Linework was reviewed by expert opinion at subsequent ecoregional priority setting workshops (10-14 August, 1999). Additional information is provided in Conservation International do Brazil (2000).
Andrade-Lima, D. 1975. A vegetação da bacia do Rio Grande, Bahia: nota preliminar. Revista Brasileira de Biologia 35: 223-232.
Andrade-Lima, D. 1981. The caatingas dominium. Revista Brasileira de Botânica 4: 149-153.
Conservation International do Brazil, Fundacao SOS Mata Atlantica, Fundacao Biodiversitas, Instituto de Pesquisas Ecologicas, Secretaria do Meio Ambiente do Estado de Sao Paulo, SEMAD/Instituto Estadual de Florestas-MG. Brasilia. 1999. Avaliacao e acoes prioritarias para a conservacao de biodiversidade de Mata Atlantica e Campos Sulinos, MMA/SBF, 2000. 40p.
Experts workshop for ecoregional priority setting. 10-14 August, 1999, Atibaia, Sao Paulo, Brazil
Fundação Instituto Brasilero de Geografia Estatástica-IBGE. 1993. Mapa de vegetação do Brasil. Map 1:5,000,000. Rio de Janeiro, Brazil.
IBGE. 1992. Manual técnico da vegetação Brasileira. Rio de Janeiro: Fundação Instituto Brasileiro de Geografia e Estatística.
Mauro, C.A., M. Dantas, and F.A. Roso. 1982. Geomorfologia. Pages 205-296 in S.D. Folha, editor, Brasil, MME/SG/ Projeto RADAMBRASIL, Brasília: geologia, geomorfologia, pedologia, vegetação e uso potencial da terra. Rio de Janeiro: Ministério das Minas e Energia.
Raposo, M. A. 1997. A new species of Arremon (Passeriformes: Emberizidae) from Brazil. Ararajuba 5: 3-9.
Ratter, J.A., G.P. Askew, R.F. Montgomery, and D.R. Gifford. 1978. Observations on forests of some mesotrophic soils in central Brazil. Revista Brasileira de Botânica 1: 47-58.
Silva, F.C.F. 1989. Vegetação. Pages 107-122 in A. C. Duarte, editor, Geografia do Brasil - Região Centro-Oeste, vol. 1. Rio de Janeiro: Fundação Instituto Brasileiro de Geografia e Estatística.
Silva, J.M.C. and D.C. Oren. 1992. Notes on Knipolegus franciscanis Snethlage, 1928 (Aves: Tyrannidae), an endemism of central Brazilian dry forest. Goeldiana Zoologia, 6: 1-9.
Silva, J. M. C. and D. C. Oren. 1993. Observations on the habitat and distribution of the Brazilian three-banded armadillo (Tolypeutes tricinctus), a threatened Caatinga endemic. Mammalia, 57: 149-152.
Silva, J.M.C., and D.C. Oren. 1997. Geographic variation and conservation of the Moustached Woodcreeper (Xiphocolaptes falcirostris), an endemic and threatened species of northeastern Brazil. Bird Conservation International 7:263-274.
Wege, D.C., and A J. Long. 1995. Key areas for threatened birds in the Neotropics. Cambridge: BirdLife International.
Prepared by: Jose Maria C. da Silva
Reviewed by: In process