The Saharan zone of Mali, an area of fixed dunes and false steppes, contains vegetation made up of thick-leaved and thorny plants (mimosas and gum trees). The vegetation of the Sahelian zone resembles that of the steppes, with thorny plants and shrubby savannas. There are two main vegetation zones that correspond to the climatic regions of Sudan and the Sahel in the Sudanic zone, localized forest corridors are found along the Guinean border and in the river valleys; the rest of the area is covered with Savannah. The Sudanese zone is an area of herbaceous vegetation; its trees are bastard mahogany, kapok, baobab, and Shea.
The incidence of trees decreases to the north as the Sudanic zone merges with the Sahel. The Sahel is characterized by steppe vegetation, notably drought-resistant trees as the baobab, doum palm, and Palmyra. These trees also disappear to the north, where short, thorny plants such as the mimosa, acacia, and cram-cram, a member of the grass family) grow; all vegetation is absent in the far-north region of the Sahara. Beginning in the latter half of the 20th century, deforestation overgrazing, and repeated episodes of drought served to greatly speed the rate of naturally occurring desertification, resulting in the encroachment of the desert on the Sahel.
The Inner Niger Delta is also known for its large waterfowl breeding colonies, with 80,000 breeding pairs of birds within 15 species of cormorant, heron, spoonbill, and ibis (Denny 1991). The Inner Niger Delta is also a breeding stronghold for the endangered West African subspecies of black-crowned crane the delta is essential waterfowl habitat because it remains wet in the dry season long after other areas dry up. A notable non-wetland bird species is the endemic Mali fire finch which is found only in Mali and largely confined to the delta area. The river Prinia is considered near-endemic to this Ecoregion. The vast floodplains also provide a habitat for the Nile crocodile.