Coastal Stream Salinity and Its Impacts on Pemba Agriculture

The extent of saltwater inundation of coastal streams was assessed on Pemba Island near agricultural areas in northeastern and northwestern regions of the island. Conductivity and pH were measured from water samples collected at various distances along the stream to determine the extent of salinity at different points in the tidal cycle. This salinity data, as well as the context of recent weather events, runoff, and geological characteristics of the region were used to determine the primary factors that influence changes in surface water salinity. The primary factor that influences surface water salinity was determined to be changes in stream discharge as a result of recent precipitation events or anthropogenic modifications. The impacts of these alterations are predicted to be amplified by climate change events such as sea level rise, storm surges, and changing precipitation patterns as well as increased anthropogenic usage. Implications of increased surface water salinity include lowered crop yield, abandoned farms, food and water scarcity, and negative economic impacts. Eastern Pemba was determined to be more affected by surface water salinization at present and will continue to be affected if serious mitigation strategies are not implemented