Burkina Faso is fairly flat, with an extensive peneplain that covers about three quarters of the country; elevations range from 250 to 400 m. The Koutiala Plateau (PK), a sandstone block situated in the country’s southwest, is the highest and most rugged part of the country. Several rivers cross Burkina Faso; all are tributaries of one of three major rivers: the Volta, the Comoé, and the Niger.
The large northern ecoregions, Liptako Sahel (LIP), Gondo-Mondoro (GM), and Gourma Malien (GR), belong to the Sahelian Region and are dominated by shrub savanna and steppe. Moving south, the Plateaus of Samo, Gourmantché (PG), and the Nord Plateau Mossi (NPM–North Mossi Plateau) dominate the north-central part of the country, where population density is high. The Mossi people have been farming here for generations, almost exclusively planting millet and sorghum, particularly in the numerous valleys and low-lying areas (Marchal, 1977; Dugué, 1993). The southern ecoregions, from the Pendjari plains (PEN) in the east, to the Bwa Plateau and Comoé Poni Basin (PONI) in the southwest, cover a wide bioclimatic gradient. With rainfall varying from 650 mm to over 1,000 mm, they extend over the more humid Sudanian Region. The more favorable climate and permanent rivers make them quite suitable to agriculture, with cash crops becoming increasingly important. Village of Oursi on the edge of the Mare d’Oursi, a wetland of international importance for Palearctic bird migrations.