Remote sensing the hydrological variability of Tanzania's Lake Natron, a vital Lesser Flamingo breeding site under threat

Abstract

Landsat satellite imagery was used to investigate the ecohydrological sustainability of Tanzania's Lake Natron. The lake is of critical importance as the sole breeding site for East Africa's population of Lesser Flamingos (Phoeniconaias minor), a species which is classified as near-threatened due to decreasing numbers and limited suitable breeding sites (IUCN). Lake Natron is threatened by two proposed developments: a multi-purpose dam, to be built on the Ewaso Ngiro (South) River (45% of the lake's catchment area), and a soda ash extraction factory. Both developments will significantly alter the hydrology and ecology of the lake and could impact flamingo breeding. In addition, local environmental change and global climate change over the past 50 years have altered the hydrological characteristics of the catchment.Archival Landsat imagery (1984–2011) has been used to establish baseline data about the past hydrological variability of the lake by applying the Modified Normalised Difference Water Index (MNDWI). A time series of lake surface area has been produced which shows a high degree of variability in lake levels. Comparison to infrequent observations of flamingo breeding at Natron are consistent with the prevailing hypothesis of the importance of receding lake levels. Analysis of lake features in the imagery, including the presence of salt islands, has been used to set lower and upper limits to lake areas suitable for flamingo breeding. Our results will assist the future sustainable management of Lake Natron and will contribute towards Lesser Flamingo conservation.