Mauritania is losing every year 10.000 hectares of forest zones , an area equivalent of 15.000 football pitches, revealed recently a steady on “Environment profile in Mauritania” financed by the European Union. This illustrates the alarming situation facing this African country of 1,1 million Kilometers square, more than 80 per cent of it are desert lands. Deforestation is therefore one the core environmental challenges Mauritania has to overcome alongside the management of water, cleanness and rubbishes.
Arid zone is considered as the largest ecological entity of Mauritania and includes the areas located among the north border except the coastal belt of Atlantic Ocean. It covers 810.000 Kilometers square and includes the regions of Tiris Zemmour, Adrar, Tagant, Dakhlet Nouadhibou, Inchiri, Oualata, Tamchekett, Boumdeid, Magta Lahjar, Boutilimitt et Ouad Naga.
Protection of roads against moving sand dunes
The Mauritanian authorities had begun to address the scourge of deforestation since the early 1980s with the settlement of “Greenbelt” of Nouakchott, the young capital threatened by the regular advance of sand dunes. This project had aimed to plant trees around the city to protect the buildings and road infrastructures against sand dragged by the frequent winds of the long drought of 1970s and 1980s. During this period, the rainfall was reduced to 40 to 50 percent of its prior levels, reaching 77 to 176 mm per year. As a consequence, vegetation cover was destroyed and the sands began to move. According a study undertaken by foreign experts, A.M. Jensen and M.S. Hajej, the 150 Km road linking Nouakchott and Boutilimitt (south) was sanded over for more than 60 per cent of its length by 1991.
Two approaches have been followed to face this destructive impact of deforestation on road infrastructures witch represent one of pillars of socioeconomic development of the country. The first consists of protection of the road by setting up, over an area of 150 m wide, a grid of woven fencing made from the flexible branches of the indigenous shrub Leptadenia pyrotechnica, with rows 20 to 40 m apart. In the grid between fences, various trees species (Balanites, Leptadenia, Parkinsonia and Prosopis species) were planted. Each seedling received a total of 200 liters of water during the first years. The system was maintained by replacing sanded over fences by new ones.
The second approach introduces an artificial dune called a “counter dune” witch was constructed parallel to and 50 m to the north of he road, protected by two rows of the same kind of Leptadenia fencing. This counter-dune stopped sand from crossing the road in the form of dunes, while letting loose sand cross.
In both approaches, the dunes between the protective system and the road had been cleared away by the wind after a year and a half, and the road stayed clear of dunes over the period that the system was maintained. But three years after the last maintenance, the road was again extensively sanded over. This indicates that continued regular maintenance is essential for all mechanical dune stabilization work.
Refinements in methods to protect roads against sanding in Mauritania show that protection is technically possible by using barriers of inert materials if rainfall is insufficient, and can be carried out mainly by afforestation where annual rainfall is above 100 mm. Wood and vegetable production from these stand could even bring in worthwhile income, especially for local households involved in the operation of stabilization of dunes.
Besides the “Greenbelt” of Nouakchott witch aims primarily protecting the capital, the most important afforestation scheme in the country was that of Magta Lahjar (360 Km south of Nouakchott) where 335 ha were planted with Prosopis juliflora, Parkinsonia aculeate and Leptadenia pyrotechnica. This greenbelt of Magta Lahjar has given total and lasting protection from sand on 7 kilometers of the road, or 50 ha of trees per kilometer of road.
The experts estimate that a belt 400 to 500 m wide will generally suffice to ensure the protection of the road and that the production from this belt could cover the maintenance costs. For Nouakchott – Boutilimitt road, the cost of counter-dunes has been calculated at 28.000 US dollars per kilometer over five years and it is estimated that their annual maintenance costs level out at 2.500 US dollars per kilometer from the fourth year onwards. These costs are economically more profitable than those spent annually for mechanical road clearance with large machines such as bulldozers witch level out at 13.600 US dollars per kilometer.
The cost of afforestation has been estimated at 450 US dollars per hectare with no watering, or 500 US dollars per hectare with 20 liters of water at the time of planting. A forest strip 200 m wide will thus cost between 8.900 and 10.200 US dollars per kilometer. The income from forest product could provide an estimated additional income of 760 US dollars per kilometer per year. In addition, the mechanical road clearance costs are paid mostly in foreign currency while this proportion is only 20 per cent for counter-dunes and 10 per cent for afforestation.
Sensitization on environmental stakes
On an other side, the Mauritanian government undertakes annual operations of aerial sowing at the beginning of the rain seasons on wide areas around the main roads in the country. This aims to regenerate the vegetal cover lost during the drought period. Moreover, the ministry of energy conducts periodic campaigns to sensitize households on the use of butane gas for the tasks of cooking with as goal to avoid the cutting down of trees motivated by search of wood.
The global results of environmental combat remains modest but the most important is that the fight against the desertification has become nowadays a part of the technical and socio-economic tradition in the action of ONGs, cooperatives and simple individuals. The creation of a governmental autonomous institution in charge of these issues, “the Center of Fighting against Desertification” remains widely expected.
Maarouf Ould Oudaa
technorati tags:sand, desertification
