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CAATINGA OF NORTH-EASTERN BRAZIL
GeographyThe "caatinga", the north-eastern floristic province of Brazil (Andrade-Lima 1981), constitutes one of three arid nuclei in South America, together with the Guajira Peninsula along the Caribbean coast of Colombia and Venezuela, and the dry belt that extends from Argentina through Chile and Peru into Ecuador (Ab'Sáber 1980). Each of these three regions represents a different geological province and is subject to a different climatic regime, and each has originated very distinct xeromorphic vegetation. The geology of the caatinga is in essence not much different from that of the Upper Rio Negro region (CPD Site SA6). Both originated from very old Precambrian rocks, severely degraded during the Tertiary, and overlain by more recent marine sandstones and other sediments. As in the Upper Rio Negro, there are remnant crystalline outcrops, including monolithic mesas and isolated mountain ranges (Ab'Sáber 1977; Fernandes and Bezerra 1990). Climatically the caatinga region can be considered one of the more complex areas in the world, being at the crossroads or convergence of several highly unstable winds coming from north, south, west and east (Nimer 1969; Andrade-Lima 1977). The most significant winds are the northern currents, with an intertropical convergence centre at c. 5°N, which influence rainfall as far as 9°-10°S. The climate is largely Köppen BShw (hot, semi-arid, with summer rains) or BShw´ (hot, semi-arid, with summer and autumn rains). The rainfall is influenced by the equatorial Atlantic, southern Atlantic and equatorial continental masses, and varies between 200-800 mm (rarely 1000 mm) annually, with a 35 month rainy season and 7-9 dry months (roughly May-November). Rainfall is highly irregular, leading to catastrophic droughts and floods. The temperature is isothermic, with means varying between 25°-29°C. VegetationThe caatinga as delimited in Map 55 does not correspond to a single type of vegetation, but is a broad mosaic of types. Towards the coast, the caatinga is replaced by remnants of the Atlantic Coast forest (Mata Atlântica); inland, the caatinga merges with no clear limits into the "cerrado" (see CPD Site SA21). Interspersed with the caatinga are low mountains with uplands that are much more humid, containing elements ("brejos de altitude") of the Atlantic and Amazonian forests, with trees 30-35 m tall. General characteristics of the caatinga elements include total loss of leaves during the dry season, small and firm (xeric) leaves, intense branching of the trees from the base (giving them a shrubby appearance) and the presence of succulent and crassulaceous species (Romariz 1974). Most authors recognize two main types of caatinga: dry caatinga ("sertão") located in the interior and more humid caatinga ("agreste") toward the coast. Eiten (1983) divided the caatinga into the following eight categories: 1. Caatinga forest, or low (8-10 m) xerophytic deciduous tropical broadleaved forest, with closed canopies, and the trees having a ground coverage over 60%. This robust formation occurs where there is sufficient rain and the soils are deep enough. 2. Arborescent caatinga, with the shrubby subcanopy not closed, and tree coverage 10-60%. 3. Arborescent-shrubby closed caatinga, or low xerophytic deciduous open tropical broadleaved forest with closed scrub, where the tree coverage is 10-60%. This is the most common form of undisturbed caatinga, sometimes called "carrasco". 4. Arborescent-shrubby open caatinga, with the total ground coverage of trees, shrubs, cacti, bromeliads, etc. between 10-60%. 5. Shrubby closed caatinga, or xerophytic deciduous or semi-deciduous closed tropical broadleaved scrub; the thoroughly deciduous scrub is more common. 6. Shrubby open caatinga, or xerophytic open tropical scrub, which can be composed of deciduous broadleaved species, cacti and bromeliads, or mixtures of the same. Coverage varies between 10-60%. Common throughout the caatinga on very shallow soils or rocky outcrops. 7. Caatinga savanna or xerophytic short-graminose tropical savanna with deciduous broadleaved scrub; this formation is usually called "seridó". 8. Rocky caatinga savanna or xerophytic sparse tropical scrub, in which both scrub and graminose elements have ground coverage of less than 10%. This formation occurs on pavements and outcrops of massive rock, with the plants interspersed in cracks and hollows. FloraThe flora of the caatinga region is poorly known. Humid sierras have elements (brejos de altitude) of both the Amazonian and the Atlantic Coast forest floras. Fernandes and Bezerra (1990) postulate that before the breakup of Gondwanaland in the Cretaceous (c. 90-95 million years ago), the north-east of Brazil together with the adjacent part of Africa (e.g. Nigeria) constituted a bridge between those two floras, which were probably not distinct. Certainly, fossil evidence indicates that a great part of the north-east was covered by tropical rain forests (Bigarella, Andrade-Lima and Riehs 1979; Lima 1979; Fernandes and Bezerra 1990). Pockets of cerrado also occur, suggesting that in the past this vegetation type occupied a significantly larger area (Fernandes and Bezerra 1990). Moreover, at some time in the past the dry caatingas formed part of a much larger dry belt, as evidenced by: (1) the occurrence of the same species in the chaco/pantanal complex, for example Apuleia leiocarpa, Geoffroea superba and Peltophorum dubium, (2) the presence of vicariant species such as Copernicia prunifera/C. alba and Ziziphus joazeiro/Z. mistol, and (3) many other species affinities in genera such as Astronium, Aspidosperma, Schinopsis, Capparis, Mimosa and Jatropha (Rizzini 1963; Fernandes and Bezerra 1990). In the caatinga itself, the most representative tree species include Mimosa tenuiflora, M. caesalpinifolia, Caesalpinia microphylla, C. bracteosa, C. ferrea, C. macrophylla, Auxemma oncocalyx, A. glazioviana, Patagonula bahiana, Fraunhofera multiflora, Amburana cearensis, Schinopsis brasiliensis, Cavanillesia arborea, Cereus jamacaru and Astronium urundeuva. The shrubby-scrub elements include Caesalpinia bracteosa, C. pyramidalis, Capparis ico, C. jacobinensis, Croton compressus, C. sonderianus, Lantana camara, Jatropha gossypifolia, J. mollissima, Piptadenia aculeata, Mimosa malacocentra, M. tenuiflora, Cordia leucocephala, Combretum leprosum, Luetzelburgia auriculata, Stylosanthes humilis, S. scabra, S. gracilis, S. guianensis, Aspidosperma pyrifolium, Hyptis suaveolens, Borreria verticillata, Centrosema brasilianum, Ipomoea asarifolia, Aeschynomene monteroi, A. filosa, A. americana, Zornia latifolia, Z. reticulata, Sida glomerata, S. galheirensis, Senna uniflora, Waltheria ferruginea, Melochia americana, Melocactus bahiensis, Discocactus placentiformis and Opuntia inamoena. The grasses include Paspalum, Aristida, Cenchrus and Setaria. Other discrete vegetation types associated with the caatinga are distinctive palm stands. The most common are "carnaúba" stands ("carnaubais"), where the principal component is Copernicia prunifera, and "babassu" stands ("babaçuais"), formed mainly by Orbignya phalerata. Other important stands include "tucúm" palms (Astrocaryum aculeatissimum) and "macaúba" palms (Acrocomia aculeata). The dry forests associated with the caatinga are between 500-600 m above sea-level and differ in general vegetation although caatinga elements are present. The most characteristic species include Triplaris gardneriana, Tabebuia serratifolia, Tallisia esculenta, Spondias lutea, Ceiba glaziovii, Astronium fraxinifolium, Guazuma ulmifolia, Anadenanthera macrocarpa, Pithecellobium polycephalum and Melanoxylum brauna. Among the most common species in the humid sierras, which are between 600-1000 m above sea-level, are Cedrela odorata, Didymopanax morototoni, Lecythis pisonii, Pithecellobium polycephalum, Manilkara rufula, M. subtriflora, Hymenaea courbaril, H. martiana, Inga fagifolia, Gallesia gorasema, Lonchocarpus obtusus, L. sericeus, Cordia tricotoma, Machaerium amplum, Symphonia globulifera, Pterocarpus violaceus, Zollernia ilicifolia, Dalbergia variabilis, Jacaratia dodecaphylla and Pilocarpus jaborandii. Evidence of the caatinga as a separate floristic province is given by its endemics (Fernandes and Bezerra 1990; Andrade-Lima 1981). Endemic genera include Moldenhawera, Cranocarpus (Leguminosae); Fraunhofera (Celastraceae); Apterokarpos (Anacardiaceae); Auxemma (Boraginaceae); and Neoglaziovia (Bromeliaceae). Among the endemic species are Cavanillesia arborea, Bursera leptophloeos, Ceiba glaziovii, Aeschynomene monteroi, Mimosa caesalpinifolia, M. tenuiflora, Pilosocereus gounellei, P. squamosus (= Facheiroa squamosa), Cereus jamacaru, Patagonula bahiana and Calliandra depauperata. Useful plantsThe caatinga has many useful species. The legumes and grasses are of great importance as sources of forage for arid lands, including Stylosanthes, Zornia, Paspalum, Macroptilium, Galactia, Vigna, Centrosema, Aeschynomene, Chamaecrista, Desmanthus, Panicum and Digitaria. Many species are valuable sources of food, with many used locally as fruit, e.g. Tallisia esculenta, Spondias lutea ("umbú"), Spondias tuberosa, Lecythis pisonii, Manilkara rufa and Hancornia speciosa ("mangabá"). Important caatinga timber species include Anadenanthera macrocarpa, Ziziphus joazeiro, Amburana cearensis, Astronium fraxinifolium, A. urundeuva, Tabebuia impetiginosa, T. caraiba and Schinopsis brasiliensis, as well as those found in patches of other types of vegetation, e.g. Cedrela odorata, Dalbergia variabilis, Didymopanax morototoni and Pithecellobium polycephalum. Among the medicinals are Pilocarpus jaborandii, which as well as Amburana cearensis is officially listed as threatened. The palms are of special importance in that they constitute the backbone of the local domestic economy in many parts of the North-east. Rural populations rely heavily on extraction from babassu (babaçú) (Orbignya phalerata) (May 1992), carnaúba (Copernicia prunifera), tucúm (Astrocaryum aculeatissimum) and to a lesser extent macaúba (Acrocomia aculeata), and many species of Syagrus, Scheelea and Attalea. Social and environmental valuesThe region contains a complete sequence of human occupation extending from c. 12,000 years ago, including the most abundant examples and diversified traditions of rock art from South America (Schmitz 1987). North-east of Brasília in the State of Piauí, in Serra da Capivara National Park (1000 km²) is an archaeological site claimed to be the most ancient in the Americas, purportedly some 50,000 years old, but its dating has not yet been settled (Meltzer, Adovasio and Dillehay 1994). The north-east of Brazil has the largest population concentration in the country, as well as the poorest people. The so-called triangle of drought, which includes practically all the vegetation described, supports over 60 million inhabitants. The social situation is extremely complex, with a large majority of the rural population depending upon extractivism for a large part of their livelihoods. For example, over half of the population of Maranho and Piauí states depend on babassu for c. 50% of their income (cf. May 1992). In other areas of the North-east, the same can be said for other species. Decline of caraiba woodland (dominated by Tabebuia caraiba) along the São Francisco River in Pernambuco and Bahia between Juazeiro (or perhaps Remanso) and Abaré may have contributed to the endangerment of the nearly extinct Spix's macaw (Cyanopsitta spixii) (Juniper and Yamashita 1991). Economic assessmentThe local flora is the source of livelihood for many people. Some of the extractive species, including most of the palms and fruits, have a fair to high potential under cultivation. The babassu, macaúba and tucúm palms are all potential commercial sources of high quality lauric oil, with macaúba also having a high percentage of oleic oil. Among the fruits, "umbú" (Spondias lutea) and "mangabá" (Hancornia speciosa) probably are the most promising. Large parts of the region are being put under irrigation, especially in the valley of the São Francisco River. Overall this is very promising, as the soils for the most part are fertile, and without the severe aluminium limitations of the cerrado and Amazon Basin. However, with fairly saline water and salt pans near the water table, salinization of the soil is a major threat. The region is beginning to undergo an economic boom, based primarily on irrigated agriculture; if the trend continues, it may become an important breadbasket, not only for Brazil but the world. The São Francisco Valley is exporting fruit, including grapes, papayas and melons, and will probably end up competing in world markets of these and other products. Paradoxically, this new North-east will probably co-exist with the losses described below. At the same time that some areas develop their economic potential, others will continue to be degraded, in terms of the environment and their carrying capacity for human populations. ThreatsOvergrazing by cattle and goats and excessive harvesting of fruits are seriously affecting the population structure of most of the more important species. Indiscriminate timbering for industry as well as fuelwood and charcoal is decimating the original vegetation. The region is rapidly approaching the situation of Africa in the Sahara and Sahel, where chronic drought and misuse of the environment are threatening a major catastrophe. Desertification is a serious threat, as is gradual salinization of the soils due to irrigation. Furthermore, most if not all of the over 16 conservation units in the North-east are under severe pressure from the local human populations. ConservationAs shown in Table 58, with c. 0.31% of its area (c. 3168 km²) in official principal conservation units, the North-east falls below Brazil's national average which is c. 4%. Since this region has the highest population pressure, and the population is most dependent on the natural vegetation, conservation efforts fall short of what is necessary (Andrade-Lima 1977). Map 55. Caatinga of North-eastern Brazil (CPD Site SA19)Ab'Sáber, A.N. (1977). Potencialidades paisagisticas brasileiras. Universidade de São Paulo, São Paulo. Ab'Sáber, A.N. (1980). O dominio morfoclimático semi-árido das caatingas brasileiras. Craton and Intracraton 6. Universidade Estadual Paulista "Julio de Mesquita Filho", São José de Rio Preto. Andrade-Lima, D. de (1977). Preservation of the flora of northeastern Brazil. In Prance, G.T. and Elias, T.S. (eds), Extinction is forever: threatened and endangered species of plants in the Americas and their significance in ecosystems today and in the future. New York Botanical Garden, Bronx. Pp. 234-239. Andrade-Lima, D. de (1981). The caatingas dominium. Rev. Bras. Bot. 4: 149-163. Bigarella, J.J., Andrade-Lima, D. de and Riehs, P.J. (1975) [1979]. Considerações a respeito das mudanças páleoambientais na distribuição de algumas espécies vegetais e animais no Brasil. An. Acad. Bras. Ciênc. 47 (supl.): 411-464. Eiten, G. (1983). Classificaço da vegetaço do Brasil. CNPq/Coordenação Editorial, Brasília. Fernandes, A. and Bezerra, P. (1990). Estudo fitogeográfico do Brasil. Stylus Comunicações, Fortaleza, Ceará. Juniper, A.T. and Yamashita, C. (1991). The habitat and status of Spix's macaw Cyanopsitta spixii. Bird Conserv. Internat. 1: 1-9. Lima, M.R. (1979). Paleontologia da formação Santana (Cretáceo do nordeste do Brasil). Estágio atual do conhecimento. Universidade de São Paulo, São Paulo. May, P.H. (1992). Babassu palm product markets. In Plotkin, M. and Famolare, L. (eds), Sustainable harvest and marketing of rain forest products. Island Press, Washington, D.C. Pp. 143-150. Meltzer, D.J., Adovasio, J.M. and Dillehay, T.D. (1994). On a Pleistocene human occupation at Pedra Furada, Brazil. Antiquity 68: 695-714. Nimer, E. (1969). Clima - circulação atmosférica. Paisagens do Brasil. Instituto Brasileiro de Geografia e Estatística (IBGE), Série D, No. 2. Rio de Janeiro. Rizzini, C.T. (1963). Nota prévia sôbre a diviso fitogeográfica do Brasil. Rev. Bras. Geogr. 25(1): 1-64. Romariz, D.A. (1974). Aspectos da vegetação do Brasil. Instituto Brasileiro de Desenvolvimento Florestal (IBDF), Rio de Janeiro. Schmitz, P.I. (1987). Prehistoric hunters and gatherers of Brazil. Journal World Prehist. 1: 53-126. AuthorThis Data Sheet was written by Dr Eduardo Lleras [Centro Nacional de Pesquisas de Recursos Genéticos e Biotecnologia (CENARGEN)/EMBRAPA, Caixa Postal 02-372, 70.849 Brasília, D.F., Brazil]. |
