Pollution or Protection - What Early Survey Data Shows on Rapid Waterbird Utilisation of a Newly Established Sewage Treatment Plant in Urban Ghana, West Africa

Abstract

Rapid urbanisation increasingly isolates and exerts pressure on natural wetlands, particularly in the fast-growing developing countries of the tropics, including those of West Africa. Constructed wetlands such as sewage treatment plants, may unintendedly offer wildlife protection due to prohibitive access control and limited use, thereby attracting wary and specialised waterbirds in otherwise heavily disturbed formally protected wetlands with less polluted waterbodies. We present data from a rapid survey on 1-year post-opening colonisation and use of waterbirds in a recently constructed 11 ha restricted-access sewage treatment plant, situated in Ghana’s capital, Accra. During November-December 2013 and January 2014, nine daily counts in each month produced an accumulated count of >4200 observations belonging to 26 species of waterbirds, including several important Afro-Palaearctic and intra-African migrants, hereunder ardeids, piscivorous divers, waterfowl and waders. The distributional patterns of waterbirds clearly reflected local foraging opportunities and water quality parameters in the system of 12 inter-connected waste stabilisation ponds. A nearby semi-natural wetland with cleaner waterbodies, but higher levels of human interference, supported fewer waterbirds, predominantly commensal gregarious species. Our data suggests that strict protection from disturbances outweighs possible negative implications attributed to mere pollution of waterbodies supporting various waterbird guilds, thus highlighting the potential importance of informally protected sewage treatment plants distributed in functional networks, as a complement to designated wetlands. We anticipate that establishing similar or larger plants jointly will improve sewage treatment and waterbird conservation in urban Ghana, and West Africa in general. Keywords Aquatic birds · Abundance · Colonisation · Constructed wetland · Diversity · Water quality