East African soil erosion recorded in a 300 year old coral colony from Kenya

Soil erosion is a key socio-economic and environmental problem in Kenya, which has been poorly documented due to the lack of long, continuous records. Here we present Ba/Ca records from Porites corals from the Malindi coral reef documenting the flux of suspended sediment from the Sabaki River with a sub-weekly resolution for the last 300 years. While sediment flux from the Sabaki River is almost constant between 1700 and 1900, a continuous rise in sediment flux is observed since 1900, first due to British settlements and afterwards due to steadily increasing demographic pressure on land use. The peak in suspended sediment load and hence soil erosion occurred between 1974 and 1980 when there is a five to tenfold increase relative to natural levels. This is attributed to the combined effects of dramatically increasing population, unregulated land use, deforestation and severe droughts in the early 1970's. We conclude that despite laudable attempts to instigate soil conservation measures, it is unlikely that there will be a sustainable reduction in soil erosion without a significant improvement in socio-economic conditions.