After detailed photographing of the Amazon presented some eight months ago (Pesquisa FAPESP n. 67) the Embrapa Satellite Monitoring, research center of the Federal government situated in the city of Campinas, is uncovering the marks of human occupation in the Northeast: a new history of the region can be told starting with the colored mosaic that has just been mounted from 123 satellite images, which cover nine States and more than 1.3 million square kilometers (km2). The marks are evidence, on the one hand, of current economic activity – linked to irrigation, and the expansion of agriculture and the modernization of the road network – and on the other, serious environmental problems, with risks of the loss of caatinga biome, of the salination of the irrigated lands, predatory exploration of mangrove swamp lands and the deforesting of reserves and mesas.
In the same manner as was carried out with the Amazon, the data on the work, coordinated by the ecologist Evaristo Eduardo de Miranda, has been brought together on CD-Roms and is also available via the Internet and on photographic paper. In truth, a survey of all of the National territory has already been done, in such a way that during this year the mosaics of the Southeast, South and Central-West regions will be displayed, completing an unprecedented picture of the current Brazilian landscape.
The images serve for comparative studies, above all when brought together with the cartography of the Brazilian Institute of Geography and Statistics (IBGE): a satellite image can be superimposed by a transparency over the thematic map of the same area. “The Northeast has available to it a very rich cartography”, comments Miranda. “The crossing of data with this precise image allows for problems to be detected, contoured and corrected, as well as being able to technically support these decisions”.
The meaning of colors
The Northeast mosaic reveals a dynamism that is very large: growing unbanization, transformations on a large scale in semi-arid lands – above all due to irrigation projects, settlements and modernized cattle ranching -, the expansion of mechanized agricultural occupation inthe cerrado (wooded savanna) and expressive development of the infrastructure – for example, roads and electricity networks -, resulting from the transformation commanded by the expansion of towns and of the primary sector. There is also a constant factor: the marks of the destruction of the ecosystems, mainly along the coastline from Bahia to Paraíba, through the expansion of the activities of hotel keeping and of land speculation. Miranda emphasized a somewhat unexpected use: to provide data to democratize the debate about the transposition of the waters of the river São Francisco.
A dozen researchers worked for a year and a half on the development of production programs of the mosaics and in the standardization of the colors of the North American Landsat 7 satellite images. With an approximation of up to thirty meters, the colors of the nine States are translated into environmental data. Contrary to the green and blue tones, the rose and reddish colored tones indicate environmental contrasts, as they correspond to deforested areas or to soils prepared for planting. Cultures in a precocious stage appear under these tones, in regular geometric forms. Towns and settlements also appear under rose, lilac and reddish tones.
The salt pans, typical of the State of Rio Grande do Norte have strongly bluish tones in contrast to their surroundings. Rivers, lakes, reservoirs and dams go from dark blue to black – when there are clear waters where the sunlight penetrates and is almost not reflected. As well, the clear blue tone for areas of water denounces excess of material in suspension, such as clay or pollutants.Aquicultural areas for shrimp production occupy part of the salt pans and of their surroundings, in areas neighboring to swamplands.
It is possible to identify them by the geometrical regularity of the tank, by the presence of the water and by their position close to the mangroves. The irrigation projects for fruit growing in the intermediate area of the river São Francisco, in the Petrolina-Juazeiro industrial hub, leave green marks in the caatinga vegetation. On the other hand, the expansion of cattle rearing through new caatinga management technologies lights up an alert signal to the preservation of this ecosystem.
Caatinga in danger
The hinterland of the state of Pernambuco and in the west of the state of Bahia show worrying signs regarding the loss of areas of caatinga vegetation – and this could be one of the largest environmental damages of the region. In the plateau of Araripe – a green island in the middle of the semi-arid caating on the division between the States of Ceará and Pernambuco, known for its diversity of flora -, the recent expansion of cattle rearing is provoking intense reforesting with grave implications: lowering of the vegetation, excessive use of pasture by cattle and the planting of exotic grass – the buffel, brought from Texas in the United States.
For the researcher, an acceptable environmental management would be: for each ten hectares of caatinga, only one hectare of pasture with exotic grass. In the meantime, the deforesting has been increasing considerably and, in the opinion of Miranda, the damages go a long way beyond this: “The alteration in the stratification of the soil and the intensification in the occupation of the caatinga have altered the hydric dynamics: the rainwater is not intercepted by the leaves, the soil absorbs less water – which runs off faster, provoking floods and afterwards the area becomes drier since it does not store as much water”.
There is also an alteration taking place in the potential use of this biomass. And the caatinga which normally provides firewood for kitchens, wood for building, fibers for artisan work, fruit and leaves (for example umbu and hog plum) for feeding domestic and wild animals, as well as traditional medicines. And it also acts as a reservoir of animal protein, since it sustains, above all during the dry season, the domestic animals and wild animals, hunted by the inhabitants. “All of this delicate and interlinked traditional balance could be lost”, alerts Miranda.
Another alteration is stemmed form the expansion of mechanized agriculture in pioneering areas of the west of Bahia, the south of Piauí and the south of Maranhão: There are large companies that are cultivating soya cotton and corn on a massive scale. “This activity, at the same time that it is developing the region and stimulating the construction of urban centers, has brought on one of the most intense and concentrated processes of recent deforestation in the country, up until now only slightly monitored”.
The extensive plantations of the cashew for cashew nuts exporting in Rio Grande do Norte, Piauí and Ceará are also producing significant deforestations.In the south of the State of Piauí, the deforestation of the Capivara Range has included areas of fifteen square kilometers in extension. In Cariris Novos, on the frontier with Ceará, where there are river springs, one can see an even greater deforested area of twenty five square kilometers. In the same region, the expansion of agricultural colonization in the valley of Gurguéia has rapidly reduced the native vegetation.
In Paraíba, the mosaic provides evidence of the growing urbanization of the hinterland in the regions of Souza, Cajazeiras and Pombal. And shows to what level the large irrigation project of São Gonçalo, in the center of the State, is jeopardized by the salination of the land.
The map of Rio Grande do Norte outlines the new economic occupation on the Chapada do Apodi (Apodi Mesa), at the division with Ceará, taken up by irrigation projects and intensive agriculture. On the coast, over the past ten years there has been an expansion in the shrimp farming, today one of the largest sources of income in the Northeast. In the south of Ceará, the highlight in green is the oasis of Cariri. The dunes of the extensive coastline, the hills of Baturité and Orós – the largest northeastern dam, fed by the river Jaguaribe – gives tones of green to the gray and the ochre that dominate the images.
The Mule’s Highway
The state of Maranhão forms one of the most beautiful mosaics because of the combination of colors. It has the largest areas of indigenous reserves in the Northeast and the images do not point to relevant problems of preservation, but reflect an environmental diversity that runs from semi-arid of the caatinga to the exuberant portion of the Amazon forest in the west.
“It’s a state that during the 19th century lived through an intensive agricultural development”, underlines Miranda. The earth has engrained marks of this activity: the Mule’s Highway, a roadway trod upon for more than a century by pack animals, appears in the form of a whitened line. It crosses the state from the west to the east, until the river Parnaíba, where the salted meat was embarked for other markets. Other highlights of Maranhão is the Tocantins waterway, the Carajás railroad(which brings the iron ore to the port of Itaqui) and a black point that reveals the smoke given off by the industrial hub of the pig iron works in Açailândia.
The state of Bahia needed a total of some thirty six images, each one of them of 34,000 square kilometers (km2). The Bahia scenario is also very diversified. The west, previously taken up by cerrado, now houses mechanized agriculture in an area of almost 30,000 square kilometers, with large use of irrigation through a central pivot – easily recognized by the circular greens that make up the images.
In the sub-region of Baixo Irecê, in the northwest of the state, one can see the expansion of the beans growing over the last few decades, and in the surroundings of the river São Francisco, the consolidation of small farmers in the colonization of the Ramalho Hills, on the banks of the river. In the center of the state, one can note the recent expansion of coffee growing in stretches in the region of Chapada Diamantina. And, along the more than two hundred kilometers of the state’s northern coastline, the marks of an organized and growing urban organization, linked to tourism appear.
It was more difficult to compose the mosaic of the Northeast – especially that of Bahia – than that of the Amazon, not only because of the diversity of the landscape, but mainly by the climatic characteristics: in one period of the year there is lots of rain, and in the other it is totally dry. And, frequently, the quantity of cloud cover prevented the capture of good images at the moment in which the Landsat 7 passed over the region at around ten o’clock in the morning. “In the semi-arid, the climate is cold at night and leads to the formation, by the morning, of small clouds that dissipate by mid-day”, said Carlos Assis Paniago. “These small groups of clouds are present in some parts of the mosaic because we didn’t manage to get images totally free of them”.
Paniago knows that to compose the mosaic is much more than just gluing on patches: “The joints must be corrected because the passages of the satellite are diagonals and each passage registers one day, in such a manner that the conditions of light vary and need to be equalized”. As well as making perfect joints, it transformed electronic files – so large that they can only be read in work stations – into Internet pages. The images were treated with as public domain programs the same as the others developed at Embrapa.
The northeastern mosaic has cost around R$ 1.1 million and was almost totally financed through the Ministry of Agriculture. The maps are available on the Internet (www.cnpm.embrapa.br) on CD-Roms and on maps printed on photographic paper. The CDs corresponding to each state cost R$ 40.00. At the Internet address, it is possible to obtain for free the technical details, explanations about how to consult, as well as images – in definition 50% less than those of the CDs, but with all of the information gathered together. The format is self-explanatory and allows for one to look at the images on various scales. The facility of its use stimulates access: in one year and a half, the site was visited more than 800,000 times.
Expansion of the Local Network of Embrapa’s Satellite Monitoring (nº 96/10284-9); Modality Infrastructure program; Coordinator Evaristo Eduardo de Miranda – Embrapa Monitoring by Satellite; Investment