The caatinga is a type of biome in regions with hot and dry climate, characteristic of the Northeast region of Brazil. It houses a set of plant species of arboreal and shrub size that cover the northeastern semiarid.
The soils that make up the caatinga ecosystem are sandy or sandy-clayey, stony and poor in organic matter. Plants, in the dry season, are parched and whitish – hence their name (” caa ” = forest , ” tinga ” = white ) -, they lose their leaves and show the branches full of thorns.
In the country, this domain covers an area that corresponds to 844 km 2 , 11% of the national territory, accommodating approximately 23 million Brazilians, many of them living below the poverty line. According to the IBGE, 77% of the municipalities in this region are experiencing this sad reality.
The Caatinga biome is spread over ten Brazilian states (Alagoas, Bahia, Ceará, Maranhão, Pernambuco, Paraíba, Rio Grande do Norte, Piauí, Sergipe and northern Minas Gerais).
The Domain is also present in two other spaces in South America. It is distributed to the north of Venezuela and Colombia, in an area known as guajira ; it is also on the diagonal of the Southern Cone, which passes through part of Patagonia, Andean Mountains, northern Chile to Ecuador and part of Peru.
The Domain of Caatingas has a predominance of the semi-arid climate, with drought for 6 to 8 months per year.
This climate is characterized by two distinct rainfall periods. Located in a subequatorial and tropical region, set in an interplanaltic area (Planalto da Borborema and Planalto Sertanejo), it has temperatures that vary between 25 ° C and 29 ° C, with low annual thermal amplitude.
Rainfall is scarce and poorly distributed throughout the year, occurring mainly in the first semester, with an average rainfall of 500 mm per year.
The Caatinga biome is characterized, in large part, by the vegetation cover of dry forest, consisting of xerophytic plants (grasses, shrubs and trees of low-medium size with twisted and spiny trunks, with three to seven meters in height), deciduous or deciduous (with falling leaves). In addition to these, there are cacti, with adaptations to regions with little rainfall.
The most frequent plant species in the caatinga are xiquexique, macambira, mandacaru, facheiro, juazeiro, umbu and pereiro. There are also vegetables of great economic importance, such as caroá, castor bean, carnauba and carioca.
Biogeographically, five types of vegetation that make up the caatinga can be classified:
- dry non-arboreal caatinga– formed mainly by cacti;
- dry arboreal caatinga– formed by sparse shrub vegetation;
- dense shrubbery– formation of small shrubbery ;
- higher level caatinga– formation of dense forests, formed with the aid of greater rainfall;
- and Chapadão do Moxotó caatinga– endemic formation of this plateau area, with arboreal cactuses in the shape of “candelabra”.
Other plant compositions are present in the rocky soil of the Seridó hinterland, which are grasses – undergrowth.
Because of its environmental characteristics, it was long thought that the caatinga was a domain of scarce biodiversity. Recent research has contradicted these observations: there are more than 1300 different animal species in the area. However, this is the third most devastated domain in the country, behind only the Atlantic Forest and the cerrado.
The Domain of the Caatinga is known not only for the periodic intermittence of a large part of its rivers, but also for them, at the end of its course, to flow into the waters of the Atlantic Ocean, unlike the rivers that irrigate other semi-arid areas in the world, which normally flow into closed depression areas.
The main river in the semi-arid region that does not suffer from the action of intermittency is the São Francisco River , also known as the “River of National Unity” – for connecting Minas Gerais to the Northeast. It is a river of great importance, as it serves as a generator of food for the riverside populations, it supplies the waters of the sertão with its waters, it serves as a transport, connecting several localities, and because it is a plateau river, it is also an energy generator.
The Caatinga relief has altitudes of up to 1,100 meters (range between plateaus from 670 to 1,100 meters), being known as a region of pediplanized interplanaltic depressions.
Its geological formation is divided into three periods:
- the top regions of the hillhave a sedimented formation in the Cretaceous Period;
- in the lower areas and escarpments, their formation is associated with the Paleozoic Period;
- the morrotesor hills witnesses of inselberg type have their training related to the end of the Tertiary Period and the beginning of the Quaternary, which explains, for this area, the titles of “badlands or carved, or high peeled.” These formations are: Planalto da Borborema, Chapada Diamantina, Chapada das Mangabeiras, Espigão Mestre, residual Chapadas do Araripe, Grande, Apodi, Ibiapaba, among others.
In the interplanaltic region, between the Planalto da Borborema and the composition of the Plateaus and Chapadas of the Parnaíba Basin, there is the Sertaneja Depression and the São Francisco River , a lowered area that accommodates part of the São Francisco River Basin.
This domain is developed over shallow or shallow soil, due to the scarcity of rain and / or the action of physical weathering, prevalent in the region.
In areas close to the riverbed, there is fertile soil. In other more distant regions, however, there are sandy soils, stony soils or even clay metamorphic rocks (phyllites), forming soil as if it were a brick floor (the litolics), inhibiting its use by losing its soil function, looking like a slab.