14 julho 2008


Foto: A millet field during the dry season, after the farmer has cleared it from remaining millet stalks. The picture is from Dalli, ca. spring 1990. Its waypoint is 14º51'10" North and 8º52'00" East, which is about 60 km south of the pictures from the 'green belt' above.

Desertification - a threat to the Sahel

Written: August 1994

For reference: Eden Foundation, Sweden (1994:1)

The Lost Treasures of Eden
Land covers 14.9 billion hectares of the earth's surface. A UNEP (United Nations Environmental Programme) study shows that 6.1 billion hectares are dryland of which 1 billion hectares are naturally hyperarid desert. The rest of the dryland has either become desert or is being threatened by desertification. One quarter of the world's population inhabit the drylands and depend on this area for their livelihood.
The desert itself is a somewhat stable environment. The landscape varies from flat terrain to lofty sand dunes and mountains. Extreme aridity and powerful winds characterise the Sahara Desert. These winds reach 100km/h, carry sand long distances, erode rocks and reduce visibility to zero in severe storms. Unprotected car windows become 'frosted' and car paint is quickly removed in such storms. Ozenda mentions that the Sahara boasts the highest shade temperature recorded in the world - 58°C in a locality in Libya - and the average maximum for the hottest month reaches 45°C in several places. Many locations experience an average annual rainfall below 25mm. Sand dunes move during violent storms and would be a huge threat if they reached farmers' fields. Deserts generally support a very sparse vegetation cover and this is certainly true of the Sahara. Wild animals live off the meagre resources and have special mechanisms to conserve water. Pastoralists use the desert where possible for grazing while isolated oases sustain date palms and other thirsty crops. These small pockets of human activity are minute compared to the vast expanse of the desert.
The misconception that the Sahel is directly exposed to the Sahara has been widely accepted. The Sahara is sometimes pictured as a sea of sand dunes washing onto the Sahel exposing farmers to waves of sand that roll in from the desert, yearly swallowing large chunks of farming land. If true it would be understandable that projects plant green belts in order to defend the Sahel from the invasion. In reality the situation is much more complex. In some places such as parts of North Africa and Mauritania the Sahara directly threatens farming land. However in Niger the pastoral zone to the north of Tanout (the town 13km N. of Eden's field station) is well vegetated with many bushes and trees. It is in fact a natural green belt that protects farmers from the Sahara.

This zone is species rich and many perennials growing there produce food in abundance. Several species grow larger there despite the lower rainfall than in the agricultural zone. The fauna includes gazelles and desert partridges. The vegetation protects the environment so little wind or water erosion occurs. A UNEP publication confirms that the natural green belt extends across the Sahel. It exists because it is closer to the desert than the agricultural zone and therefore too dry for sustainable millet production. Careless use, however, could easily destroy this zone.
From the natural 'green belt' north of Tanout, two pictures taken in November 1993 from the same spot in different directions. The waypoint of the location is 15º25'55" North and 8º5'6" East.

The agricultural zone to the south of the natural green belt also used to be species rich. Farmers in Dalli remember when it was well vegetated. "Only 100 years ago," says Malam Garba, aged 77 from Dalli, "villagers used to hunt many wild animals such as antelope, monkey, wolf, fox, squirrel, rabbit and even elephant." Malam Garba and his brother harvested 700 baskets of millet from their field 40 years ago which provided a surplus for both their families. Many trees and shrubs surrounded their fields including edible species. Villagers did not need to cut down trees for firewood because enough dead wood was available. Noumau, aged 45, comes from a village NW. of Tanout. His grandparents used to hunt lion, elephant, giraffe, ostrich, addax, antelope and deer for meat and hides. During his parents' lifetime both hunting and agriculture were practised, but hunting was more important.

Nowadays the wind easily erodes the soil because there is little vegetation, so the landscape is brown and desolate for most of the year. Loose sand even moves onto the road.
A millet field during the dry season, after the farmer has cleared it from remaining millet stalks. The picture is from Dalli, ca. spring 1990. Its waypoint is 14º51'10" North and 8º52'00" East, which is about 60 km south of the pictures from the 'green belt' above.
Malam Garba says that rains are lighter and more erratic than before. The daily showers that used to fall during a 25 day period in the rainy season have now ceased. Noumau explains that farmers in his village cultivate millet, irrigate winter cash crops and hunt only a little for deer. Nowadays Malam Garba's field is three times larger, but his harvest is only 1/7 of what it used to be 40 years ago.

This is just sufficient for his family. The lower yields have been caused by the destruction of perennials that used to shelter the annuals and contribute to soil fertility.
Decimation of vegetation is a widespread problem that extends far beyond Dalli. According to National Geographic trees once protected Khuwei village in western Sudan. These days the grain yields are insufficient and a villager talks of always being hungry. Sand dunes even rise to roof level. These dunes did not blow in from the Sahara, 200km away, but have formed from eroded soil inside the agricultural zone where the trees have been cut down. The threat to Dalli and Khuwei farmers does not come from the Sahara Desert itself but from desertification within the agricultural zone.
Desertification is a man-induced process that leads to soil nutrient depletion and reduction of biological productivity. In the Sahel slashing and burning of natural forest and bushland in order to clear land for annual agriculture is the main cause of this destruction. Farmers continue to degrade their environment in the agricultural zone even after the decimation of perennials. A few months after harvest, farmers cut the millet stalks and burn them leaving their fields exposed to strong winds until the next sowing season. These winds blow away the top soil, uproot seeds and seedlings and suffocate seedlings and plants where soil later accumulates. The Director of the National Department of the Environment in Niger said at the Direct Seeding seminar in Zinder that 250,000 hectares are being lost each year in Niger through desertification. This is equivalent to 2,500 km², an area about the same size as Luxembourg. The Department of the Environment, Zinder, explained that firewood destined for Zinder town is collected up to 200 km away.Many people are concerned about the unsustainable slash-and-burn of rain forests in Brazil and its terrible effects on the local population through soil fertility loss. But few know about the similar destruction in the Sahel even though the consequences are just as dire for the Sahelians. Projects have tried to revegetate the region themselves but it is too vast. It is more appropriate for farmers to revegetate their own land as they are cultivating throughout the Sahel and can cover the area more effectively.
Delehanty shows in his study of central Niger how annual agriculture contributes to the process of desertification. He links this process to events that took place during the colonial period. The colonial administration wanted to make Niger profitable and saw peanut cultivation for export as a means of doing this. (The level of taxation was loosely linked to peanut prices, so increases in peanut prices resulted in higher taxes paid to the administration in southern Niger.) Central Niger was seen as a granary to feed the peanut cultivators of the southern part of the country. During the 1920's peanut seeds were distributed to farmers and the colonial administration licensed private firms to set up a peanut marketing network. Peanut exports from the Zinder region rose from 4,500 metric tons in 1928, to 78,900 metric tons in 1970. Peanut exports from the Tessaoua area (near Zinder) also increased rapidly until 1970 but then declined due to lower prices and appearance of a disease. Meanwhile millet cultivation replaced peanuts and rose from 72,000 hectares in 1970 to 162,000 hectares in 1980. (According to Gillet millet fields occupied 80% of the area by 1981 in the Zinder region.) The expansion of annual cropping has resulted in a rapid decline of stable perennial vegetation and desertification over wide areas. An area of species rich woodland called Dana in the Tanout region (near Gangara) covered several hundred hectares in 1952 and villagers were hunting wild animals. In 1960 there were monkeys in Dana, but by the mid 1980s only relics of this woodland remained. Gillet states that in 1964, the tree species Terminalia avicennioides was plentiful around Maradi (south of Dana), but had become extinct in Niger by 1981. Delehanty cites a report by the colonial administration from the Zinder Department in 1951 expressing concern over the expansion of annuals at the expense of bush and forest, resulting in impoverished soils and extension of sand dunes. The report added that they may have to give up peanut production. This warning was clearly ignored.
It is also alarming how over-optimistic projects have mechanically cleared large areas of the green belt of all vegetation in order to make way for annual crops. Local villagers recently grew millet in one such area but then abandoned the land leaving it totally bare because it was too far north for sustainable millet production. If they continue this practice, breaches will be made in the green belt. The desert will advance very quickly into the agricultural zone through the breaches leading to desert encroachment, which is the invasion by the desert onto agricultural land.

Some projects plant green belts in order to protect agricultural land from this menace. However, one or just a few species are usually planted. These species can supplant native flora making the area species poor.
Land used for millet cultivation has become barren sand dunes in east Niger and north east Nigeria. Large livestock herds graze perennial vegetation where it is still in place. Neither livestock nor firewood collection is responsible for the denuded areas away from large population centres. (During droughts and famines however, pastoralists cut trees to feed their animals which does affect forested areas.) It is both more difficult and costly to repair the damage already done to the agricultural land and the natural green belt than to maintain them in good condition.
Man can either destroy his environment or be constructive by solving problems that occur within it. By increasing the population of perennials in the agricultural zone, farmers become agents for the stabilisation of their land. They then live in harmony with their environment in a symbiotic relationship where the land benefits from man's presence through the increased number of perennials, and man benefits from his own active control of desertification.
Eden's solution to desertification is for farmers to stabilise their environment themselves by intercropping edible perennials in their fields. Perennials act as anchors that stabilise the soil against wind and water erosion and also improve fertility. This protects the natural green belt because farmers respect perennials if they cultivate them making it less likely that they cut them down. Where farmers intercrop annuals with perennials, their land will produce more food both from the perennials and from increased yields from annuals lessening the pressure to move into the natural green belt. Eden's solution leaves farmers to revegetate by their own initiative. They then retain their dignity as Westerners are not revegetating their land for them but at the same time Eden supports their work by researching species that they will use.
Literature consulted for this article:
Delehanty J.M. (1988) The northward expansion of the farming frontier in twentieth century central Niger. (Volumes I and II) Ph.D. Thesis, University of Minnesota, USA
Direction Départementale de L'Environnement, Département de Zinder (1992) 'Situation du Secteur Environnement', presented at seminar titled "Reforestation by direct seeding" 5-7 November 1992.
Director of the National Department of the Environment (1992) Communication made at seminar titled "Reforestation by direct seeding" 5-7 November 1992.
Ellis William (1987) Africa's Sahel - The stricken land. National Geographic. August 1987.
Gillet H. and B.P. de Fabregues (1982) Quelques arbres utiles, en voie de disparition, dans le centre-est du Niger. Rev. Ecol. Terre Vie. 36: pp. 465-470.
Grainger Alan (1990) The Threatening Desert. Earthscan Publications Ltd.
Ozenda Paul (1983) Flore du Sahara. 2e edition. Centre National de la Recherche Scientifique, Paris, France.
UNEP (1992) World Atlas of Desertification. Pub. Edward Arnold, UK

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