MIGUEL TREFAUT RODRIGUES / USPBefore the dry season: at the bottom of ponds, fecundated eggsMIGUEL TREFAUT RODRIGUES / USP
In the 1960’s, Nelson Pereira dos Santos in Vidas Secas [Barren Lives] and Glauber Rocha in Deus e o Diabo na Terra do Sol [Black God White Devil] showed the backlands of the northeast as an inhospitable, dry and almost lifeless environment, persecuted by a scorching Sun. Now, the same space reappears in Abril Despedaçado [Behind the Sun], by Walter Salles, and in Baile Perfumado [Perfumed Ball], by Paulo Caldas and Lírio Ferreira. Coincidentally, in the domains of science as well, a new view is emerging of the Caatinga ( Semi arid), the only entirely Brazilian ecosystem and the least studied. A scenario of intricate ecological processes, this environment know as the backlands (sertão) – an area of 800,000 square kilometers, which corresponds to almost half of the nine states of the Northeast – reveals itself to be much richer in exclusive species of plants and animals, such as fish, lizards, birds and mammals, than one used imagined. In the 800 pages of the book Ecologia e Conservação da Caatinga [Ecology and Conservation of the Caatinga], launched this month, a group of 35 specialists from the Northeast itself and from the Southeast synthesizes the last 200 years of research, adds the most recent discoveries, and does away, for once and for all, with the notion that this ecosystem, where 20 million persons live, is homogeneous and uninteresting.
At the bottom of the lake – As in the driest region of the Caatinga there are years when it rains only some 300 millimeters a year – six times less than in the Atlantic Rain Forest or in Amazonia, the plants and animals have adapted themselves so as to survive with the minimum of water, without losing out in beauty or diversity on account of this. The plants have small leaves and thick bark, which reduces the loss of water. In the extreme cases, cacti like the mandacaru (Cereus jamacaru) and xique-xique (Pilosocereus gounellei) live with leaves that are no more than thorns. Amongst the fishes, at least 25 of the 240 species identified manage to postpone birth, while they wait for the rains: they spend the greater part of the time in the form of eggs, which are only hatched when the waters arrive, at some moment between February and May. These fish – called annual – are between 5 and 15 centimeters long and live in lakes or in ponds of water no more than a meter across, which dry up during the dry season.
But there is time to create a new generation. Before the dry season arrives, the males court the females and attract them to the bottom of these little lakes, lined with mud and sand. Next, they take a dive into the mud, the female releases her eggs and the male fecundates them. During the dry season, which may last almost a year, the embryo develops slowly inside the eggs, without bursting the shell. “The embryo remains in a sort of hibernation”, explains one of the authors of the book, biologist Wilson Moreira da Costa, from the Federal University of Rio de Janeiro (UFRJ). It was in the last few years that Costa discovered the majority of these species, which the people from the backlands call cloud fishes, for believing that they are born in the clouds, before the first rains, as if they were the fruit of spontaneous generation.
Ants and trees
Under the coordination of ecologists Inara Leal and Marcelo Tabarelli, both from the Federal University of Pernambuco (UFPE), and of ornithologist José Maria Cardoso da Silva, a professor on leave from UFPE and a vice-president of Conservation International (CI) Brazil, Ecologia e Conservação da Caatinga enjoyed financial support from the Center for Environmental Research of the Northeast (Cepan), from CI itself, from The Nature Conservancy of Brazil, and from the National Council for Scientific and Technological Development (CNPq). One of the original articles, signed by Inara, deals with the dispersion of seeds by ants in the Caatinga. Taking part in this process, which allows the seeds to germinate far from the mother plant, avoiding competition for food, are no less than 18 species of ants, to the benefit of 28 species of plants, amongst them 11 from the Euphorbiaceae family, the one to which the faveleira (Cnidosculus phyllacanthus) belongs, a tree whose fruit, when it is ripe, opens up with a snap and launches the seeds afar.
Inara discovered that the ants prefer seeds with a fatty body, the elaiosome, which provides them with food and at the same time makes it easier to transport the seeds, some of which are carried for as much as 11 meters. Ants like the leaf cutters (Atta and Acromyrmex), the thief ants (Solenosis) and the trap-door and ponerine ants (Odontomachus and Ectatomma) also eat the pulp of the fruits of five kinds of cacti and three species from the Anacardiaea family, the same as the umbu (Spondias tuberos). They remove all of the pulp of the fruits that have fallen on the ground of the forest and leave the seeds completely bare. “This behavior reduces attacks by funguses and increases the germination rates of the seeds”, says Inara.
Contrasts
The Caatinga is not just one. There are at least six types of distinct plant compositions – from the more open and lower, with trees 1 meter high, to the dense kind, with trees of up to 20 meters in height -, described by the Argentinean botanist Darién Prado, from the National University of Rosario. Over this mosaic of landscapes, there is a mixture of 932 species of plants, of which one third is endemic, for existing only there.On the dry, red soil, covered by a sky that is always blue, the whitish-gray tone of the trunks of the trees and leafless bushes, typical of the dry season, predominates, the leaves start growing again with the first rainfall. In the years of severe drought, the quantity of rain may be reduced by as much as 95%, according to meteorologist José Oribe Rocha Aragão, from UFPE.
The vegetation begins to change in the foothills of Ceará, of Paraíba and of Pernambuco. Up at the top, at an altitude of over 600 meters, it looks like another world: veritable islands of green forest, dense and humid, with trees of up to 30 meters in height. We are now in the high wet forests, which cover, for example, the Maranguape mountain range, close to Fortaleza, 30 kilometers away from the Atlantic, or the Ibiapaba plateau, now on the border with Piauí.During the dry season, the forests nurture another group of animals that show surprising diversity: the birds. 510 species live in the Caatinga, almost one third of the total found in the country, and almost double the number surveyed in 1965 by the German ornithologist Helmut Sick.
“The forests ensure the continuity of the regional ecological processes, like the migrations”, says Cardoso da Silva. “Some species that live in the Caatinga during the rainy season go back to these damp areas during the long periods of drought.” The Spix’s macaw (Cyanopsitta spixii), for example, used to leave the region of Curaçá, in Bahia, and fly kilometers to the forests to feed itself, when the pinhão (Jatropha mollissima), the faveleira or the baraúna (Schinopsis brasiliensis) no longer gave fruit. Today, the Spix’s macaws live only in zoos or nurseries – there are only 60 specimens in the world – and the species is regarded as extinct in nature: the last specimen living free was seen in October 2000.
For their ecological importance, the high wet forests are amongst the 82 priority areas for the conservation of the Caatinga, just like the dunes of the São Francisco, another space equally rich in exclusive species, between the towns of Barra and Sobradinho, in Bahia. The dunes of up to 60 meters that arise from the banks of the São Francisco river, or Velho Chico (Old Frank), the largest perennial river in the region, concentrate about one third of the species of the semi-arid, amongst them 16 species of lizards, eight of snakes, four of amphisbaenia, and one amphibian, examples of animals that are exclusive to that area. Amphisbaenia are reptiles related to snakes, without any visible scales or eyes, also called worm lizards. In a recent excursion, reptile specialist Miguel Trefaut Rodrigues, from the University of São Paulo (USP), found another new species in the dunes, Amphisbaena arda, so-called because of its whitish body with black patches. “Of all the lizards and amphisbaenia of the Caatinga, 37% are endemic to the dunes, a small territory that does not exceed 7,000 square kilometers, or 0.8% of the area of the northeastern backlands”, says Rodrigues.
It is not just the high level of endemism that comes as a surprise in the dunes of the São Francisco. The opposite banks of the river are home to lizards, snakes and amphibaenia that are very similar in appearance, but from distinct species and genetic constitution: they are sister species, like the lizards Tropidurus amathites and Tropidurus divaricatus. Both are up to 30 centimeters in length and have a brown body with black and yellow patches, but with different patterns. According to Rodrigues, it was the São Francisco itself that induced these species to arise from a common ancestor. According to the recently accepted hypothesis, the river used to run into a lake in the interior of the Northeast, not to the sea, until the end of the last glacial period, 12,000 years ago. On the banks of this lake, there used to live populations of animals adapted to sandy soils.
“When the river burst these banks, it isolated in opposite sides populations of the same species, which used to live in similar habitats”, says the biologist from USP. As a consequence, these species evolved in separated environments and originated species that are found today only on the right bank of the river or on the left (see Pesquisa FAPESP 57). The model remains the same, but the lizards up until then called Tropidurus came to be recognized as a new genus (Eurolophosaurus), and DNA analyses suggest that their origin must have been older, between 1 and 3 million years, and not so recent as was supposed.
From the Caatinga to the Chaco
Amongst mammals, the total number of species that live in the Caatinga has leapt from 80 to 143 and of endemic ones, from three to at least 20, as a result of the surveys coordinated by João Oliveira, from UFRJ. It was already known that it is only in the Caatinga that are to be found the rock cavy (Kerodon rupestris), a rodent of up to 40 centimeters; the red-nosed mouse (Wiedomys pyrrhorhinos), from 10 to 13 centimeters long, not counting the long tail, which acts as a support when it comes to climb trees; the three-banded armadillo (Tolypeutes tricinctus), the smallest Brazilian armadillo, between 22 and 27 centimeters long, which rolls up its body and looks like a ball when it feels threatened. The list of endemic species now includes the insect-eating bat Micronycteris sanborni, the marsupial Thylamys karimii, with its light gray back and cream belly, and a titi monkey (Callicebus barbarabrownae), described on the basis of material collected at the beginning of the last century and found recently in the hinterland of Bahia. Even so, according to Oliveira, the endemism of mammals from the Caatinga is still at least three times less than in the Atlantic Rain Forest or in Amazonia, in view of the very size of each ecosystem.
“The Caatinga is Brazil’s least protected ecosystem, since the full protection conservation units cover less than 2% of its territory”, says Tabarelli, who advocates the creation of new conservation units. The study by botanists Isabel Cristina Machado and Ariadna Valentina Lopes, from UFPE, stresses the need for preservation, when it reveals an unexpected wealth of specialized pollination processes: of the 147 species grasses, trees and bushes studied, 30% are pollinated by bees only, 15% by humming birds and 13% by bats. “These discoveries help to undo the myth that the Caatinga is poor in exclusive species and phenomena”, the researcher comments. For lack of evidence, the ancient idea has also fallen to the ground that the native vegetation of the Brazilian semi-arid could be a prolongation of the Argentinean Chaco. Now there is a suspicion in the other direction: some species of plants, like the quebracho (Aspidosperma quebracho), a tree of up to 30 meters in height, may have followed in the opposite direction. It was a slow migration, carried out over thousands of years, as the climate changed and the rainwater, the wind and the ants, with their habitual discretion, took their seeds from one place to another.
Republish