Review of anthropogenic threats and biodiversity assessment of an Ethiopian soda lake, Lake Abijata

Abstract

The intention of this review is to assess the impact of anthropogenic activities on the biodiversity of Lake Abijata. The lake was established as a National Park, together with Lakes Shalla and Chitu, to conserve water birds. It has high pH and electrical conductivity and is hypersaline. It presents an inhospitable limnochemical environment that limits biodiversity, although there are organisms adapted to these hostile conditions. The biodiversity of the lake is threatened by anthropogenic activities. Deforestation, expansion of agriculture, livestock, soda ash extraction and upstream irrigation led to a drop in water level and surface area, a change in physico-chemical and biological conditions, and a general deterioration in ecosystem condition. The phytoplankton community structure has switched from populations of Arthrospira fusiformis to non-Arthrospira fusiformis, zooplankton communities have moved towards small-bodied rotifers, such as Brachionus, Filinia and Lecane spp., the fishery has totally collapsed and birds, such as lesser flamingoes (Phoeniconaias minor Geoffroy) and great white pelicans (Pelecanus onocrotalus), have migrated to nearby lakes. These ecological changes over the past years point to the need for a new conservation and management plan to restore the ecosystem’s health. A few recommendations are given for lake management as mechanisms to protect the ecosystem.

Keywords: agriculture, irrigation, lake management, physico-chemical conditions, phytoplankton, rotifers