The part of the Niger river which is often referred to as Ayorou lies south-west and south of the town of the same name, 220 km north-west of Niamey. The river here is relatively shallow, due to the presence at the surface of erosion-resistant Precambrian rocks, and up to 6 km wide, with numerous small islands as well as seasonally flooded areas. This local ‘inner delta’ covers about 10,000 ha. Its character varies greatly with the level of river water, which tends to be lowest just before the wet season (April–June) and highest in December–January, since the inland delta of central Mali delays the arrival of maximum water-levels by some four months. Vegetation on the islands consists mostly of grasses and herbs, but also includes scattered trees such as Hyphaene thebaica. The riverine vegetation surrounding the islands includes Echinochloa, Cyperus and Sesbania spp. During the past 20 years, however, the river’s regime has changed considerably, due to the construction of dams and other off-takes upstream in Guinea and Mali. Average flows have decreased, as have frequency and levels of flooding.
See Box for key species. Prinia fluviatilis is likely to occur. Although never systematically surveyed, Ayorou is believed to be of considerable importance for waterbirds. Very incomplete counts were undertaken in February 1995 and in April 1997, when 33 species of waterbird were recorded. The total number counted in February 1995 was 10,907, when only 5% of the area was censused. In addition to those listed below, noteworthy counts include 2,752 Dendrocygna viduata in February 1995 and 130 Balearica pavonina in February 1984. The only large sub-population of B. pavonina between northern Cameroon and the Inner Delta in Mali breeds at isolated wetlands in north-west Niger and adjoining parts of Burkina Faso and Mali; Ayorou is likely of importance for this sub-population during the dry season.
Non-bird biodiversity: The mammal Trichechus senegalensis (VU) occurs at this site.
Pressure/threats to key biodiversity
In addition to the influence of upstream dams and associated changes in hydrology, the Ayorou area is threatened by the proposed construction of a dam at Kandadji, immediately downstream. This proposal, for the generation of electricity and for water-supply and irrigation purposes, has been under discussion since the 1960s. The various alternatives would result in a maximum water-level of between 228–241 m above sea-level, effectively drowning the present area. There may, in future, also be detrimental effects from mining developments to the west, with a tarmac road and a permanent river crossing proposed just north of Ayorou. Increasing use of the area for crop and livestock production may also become a problem. Fishing is an important activity. The area is also used for watering and grazing cattle. Grasses, some of them aquatic, are collected for cattle fodder. Agriculture takes place on a number of the islands. Hunting or poaching with shotguns is said to take place locally. The Ayorou area is best known for its Hippopotamus amphibius population which, together with the weekly market in the town of Ayorou, form a tourist attraction. Ayorou has been proposed as a protected area.