Country study Burkina Faso 
Biodiversity 

3.2 DIVERSITY OF HABITATS AND ECOSYSTEMS

The essence of the diversity of habitats and ecosystems comes from the geographical situation and the physical milieu described in chapter 1.4.

3.2.1 PHYSICAL CHARACTERISTIS OF THE HABITAT

More than 80% of the Burkinabè territory rests on a large peneplain with an altitude of 250 to 300 m hardly affected by the hydrographic network. A few small chains of steep hills emerge from distances apart (GUILOBEZ S., 1985).

3.2.1.1 vegetation

Because of its flora and vegetation, Burkina Faso is part of the vast Sudano-Zambian region. The flora is divided into two main sub-sets. One belongs to the Saharan and Sahelian dry flora, and the other to the Sudanese. In the extreme southwest, flora components of the Guinean wetland appear along the main rivers.

3.2.1.2 Classification of habitats in humid milieu

In Burkina Faso, wetland water can be classified into three (3) categories, which are: Oligotrophic water bodies (often deep with a narrow bank, poor in coastal plants), eutrophic water bodies (they are often flat and surrounded by concentric belts of aquatic plants) and dystrophic water bodies (with water rich in humid matter and poor in mineral salts).

3.2.2 ECOSYSTEMS

As mentioned in chapter 1.4.5, the present phytogeographical division shows two main domains: the Sahelian domain and the Sudanese domain, which correspond respectively to two main phytogeographical domains of the country. These two can be distinguished by their respective floral set: the Saharan and Sahelian dry flora zone (25% of the country), and the mesophile Sudanese flora zone. In the details, there are transition zones constituted by north-Sahelian, south-Sahelian, north-Sudanese and south-Sudanese sectors.

There is not yet a consensus on national nomenclature for the classification of plant formations. For the moment, plant units are classified by drawing inspiration from Yangambi's classification of vegetation types. The following nomenclature of groups of plant formation / ecosystem/ habitat has been chosen:

  • terrestrial ecosystems (natural or artificial) : sparse forest, savannah, steppes, fallows and agroforestry parks, plantation;
  • intermediary ecosystems : formations along streams and lake banks, swamps, irrigated systems;
  • hydrospheres (natural or artificial, intermittent or perennial) : vegetation of lakes, dams and ponds, phytoplankton;
  • Specialised ecosystems: terrestrial (vegetation of sandy structures), aquatic (vegetation of springs and waterfalls).

According to the Tropical Forestry Action Plan in BOGNOUNOU O., 1993, the three main types of forestry ecosystems found in Burkina Faso are distributed as follows:

Table 15: Distribution of ecosystems

Identification  Area (ha) % Territory
Terrestrial ecosystems  25 140 000 91.22 
Aquatic ecosystems 72 500 0.26
Intermediary ecosystems  371.000 1.34
Total  25 583 500 93.84

Source: OUADBA J. M., 1997

The rest of the country is covered with other types of environment, particularly dunes, towns, rocks, roads, etc. Some of these ecosystems or habitats have been the object of specific studies by technical services. They are:

  • The designated and State protected forests;
  • Some forest galleries along the Mouhoun River ;
  • The agroforestry parks of the Central Plateau;
  • Wetlands.
3.2.2.1 Ecosystem functions

Ecosystems maintain the lives of the other categories of biological diversity, including man. The richness of a country in biological diversity depends on the importance in quantity and quality of its ecosystems. The economy of Burkina Faso, as any agricultural country, depends on the functions of the ecosystems it shelters. Table 16 shows us a few examples of these functions, which benefit the development of Burkina Faso.

Table 16: List of a few functions of ecosystems.

Function  Role played by ecosystems Types of ecosystems or habitats
Production  Maintenance of fertility Forestries, clogged wetlands
Maintenance of humidity idem
Diversification of production Agricultural zones, pastoral zones, pastures, zones which can be irrigated
Prevention of erosion / Protection Slowing down of runoff water speed and winds  Ligneous and herbaceous forestry formations
Mildness of climate Shade, increase in air humidity Forestries, wetlands
Education  Availability of varied complexes Terrestrial, aquatic
Scientific  Variation of ecological systems idem
Aesthetic and recreational Diversification of species National parks
3.2.2.2 Terrestrial ecosystems

Natural forestry formations are divided into protected areas (25%) and non-protected areas (75%). The domain of forest reserve covers a total area of 2,721,857 ha, i.e. 14% of the national territory.

Among the terrestrial ecosystems, forests account for an important position. The exploitation of the documentation produced under the aegis of the ministry in charge of environment reveal the following data concerning terrestrial plant formations. Plant formations (herbaceous and ligneous) cover 93% of the national territory distributed as follows: 60% of natural formation (forests, savannahs, steppes, spotted bushes), 32% of man-made formation (fallows and agroforestry parks, plantations). The detailed distribution of plant formations is shown in table 17, following the documents produced under the aegis of the ministry in charge of environment.

Table 17: Distribution of types of plant formations.

Origins of formation Types of formation Area (ha) % Territory
Natural Gallery forests 270 000 1
Sparse forests 287 000 1
Bushy savannahs 4 291 000 16
Shrubby savannahs 10 185 000 37
Spotted tigers 387 000 1
Steppes  1 200 000 4
Man-made Fallows and agroforestry parks 8 770 000 32
Plantations  20 000 -
Total    25 410 000 92

Source: OUADBA J. M., 1997.

The herbaceous cover presents characteristics related to the phytogeographical zone in which it is found. In general, the most representative families are in the decreasing order: gramineae (monocotyledones with hollow stem), leguminous plants (dicotyledones with pod), and cyperaceae (apetalous monocotyledones with full stem).

A recent study conducted by FONTES J. and GUINKO S., 1995, on plant formations in Burkina Faso, provides the distribution of plant formations according to domains and the country's phytogeographical sub-sector, as shown in table 18.

Table 18: Distribution of terrestrial plant formations according to phytogeographical zone

Phytogeographical zones /Plant formations Area (Km2)  % Territory
SAHELIAN DOMAIN
North-Sahelian sector    
  Grassy steppe 862 0.32
  Grassy and bushy Steppe 8.619 3.18
  Shrubby steppe 18.842 6.95
  Shrubby and bushy steppe 3.304 1.22
  Aquatic grassland 165 0.06
South-Sahelian sector    
  Shrubby steppe  33.352 12.31
  Shrubby to bushy steppe 7.237 2.67
  Steppe and valley bush savannah 6.765 2.50
  Bushy savannah 287  0.11
SUDANESE DOMAIN
North-Sudanese sector    
  Bushy to wooded savannah 3.868 1.43
  Bushy to shrubby savannah 75.965 28.05
  Agroforestry parks/Savannahs-Parks 11.835  4.37
  Bushy savannah and Sourou grasslands-prone to floods 869  0.32
South-Sudanese sector    
  Shrubby and bushy savannah 33.412 12.34
  Bushy to shrubby and wooded savannah 43.891 16.21
  Bushy to wooded savannah and sparse forest 20.518 7.58
  Forest-gallery and associated aquatic grassland 434 0.16
TOTAL 270 225 97

Source: OUADBA J. M., 1997

3.2.2.3 Ecosystems of wetlands

According to the Ramsar Convention, "Wetlands are areas of swamps, marshy waste lands (peaty swamps), peat bogs or water (natural or artificial, perennial or intermittent) where the water is stagnant or running, fresh, briny (salty taste) or salted, including marine areas whose depth is not more than 6 metres deep during low tide".

Cowardin et al., in 1979, gave the following more globalising definition: "Wetlands are transition zones between terrestrial systems and aquatic systems where the water table is close to, or reaches soil surface, or where this surface is covered with shallow water."

In the Burkinabè context (a continental country), wetlands are formed by all the natural or artificial zones where water is running or stagnant, perennial or intermittent; they cover about 225 000 ha. Those are water reservoirs (dam lakes, depression lakes, and ponds), springs and flood basins. Appendix 3 shows the outstanding wetlands of Burkina Faso.

In the typology of Burkina Faso wetlands, there two categories : submerged wetlands and clogged wetlands.

a) Submerged wetlands

They include two categories:

  • zones submerged by running water;
  • zones submerged by bog water.

In the category of zones submerged by running water, the size of streams depends on the catchment area. Thus, when the former is not more than a few hectares, we have brooks, ditches or torrents; for a catchment area of a few km² to thousands of km², we have a backwater; for rivers, the size of the catchment area is hardly more than 100 000 km².

At the level of running water, there are five main streams: Mouhoun, Nakambé, Nazinon, Comoé and Pendjari. Nakambé and its main affluents flow for an average of six months a year, Nazinon for six months; only Comoé and its affluent Léraba, Mouhoun and its affluent Kou and Pendjari have an perennial flow.

Bog water concerns lakes, ponds, water reservoirs and dams. The updated inventory of surface water resources estimates the number of water reservoirs to 1300 (OUEDRAOGO R. L., 1996). The perennity of natural and artificial water bodies highly depends on their respective depth and the climatic and physiographical zone of the country.

Zones submerged by bog water are those covered by perennial water. Among them, there are two big artificial water bodies, Kompienga (216 km2 with 2 billion m3 maximum) and Bagré (250 km2 with 1.7 billion m3), have a marked hydroelectric vocation. The ponds, including the Oursi Pond (Ramsar site), which used to be big and perennial are now subject to drainage; only the Hippopotamuses Pond (which is a biosphere reserve) is saved from this situation. Map n°10 shows the hydrographic network and the water reservoirs.

b) Clogged wetlands

Clogged wetlands are those with soils that are saturated by water. This saturation may be superficial and translated into a partial submersion hardly more than a few centimetres. It may be deep and translated into the existence of some hydrophile plant species or cultivated plants on the surface, requiring an hydric supply higher than can be provided by the regional climate.

Clogged wetlands are of two types: natural superficial clogging (related to the presence of streams, lakes and water reservoirs) and artificial clogging (irrigated areas).

The type of clogged wetland we are interested in here is natural superficial clogging. Depending on clogging, there are mouillere, bogs, marshes and swamps.

The mouilleres are temporarily clogged small areas, characterised by superficial drippings affecting locally the outcrop of an aquifer groundwater. Usually, mouilleres are found on the low sides at the margin of lowland central zones. They appear in mid-August and at the end of November in south and southwest zones of Burkina Faso.

Bogs are larger than mouilleres, and they are found in the central part of lowlands or at the margin of ponds and flood basins in the south-Sudanese zone.

In Burkina Faso, natural clogging of soils is intermittent because of the character of the climate.

 

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