Are we destroying our insurance policy? The effects of alien invasion and subsequent restoration : A case study of the kromme river system, South Africa

Abstract

Securing sufficient and reliable water supply is a priority for many countries worldwide, but their efforts are hindered by widespread landscape degradation and uncertainty around future climate change. We used historical aerial photographs and mapping techniques to investigate how a South African landscape has changed over the past century. The Kromme River Catchment, a valuable water-providing catchment for the Nelson Mandela Bay metropolitan hub, has become heavily degraded. The floodplain wetlands, which historically occupied the entire valley floor, have been almost completely replaced by agriculture or invaded by the alien tree Acacia mearnsii. Some efforts have been made to restore the wetlands and control the invasive plants, but our results show that at the current rate of clearing it would take 30 years before A. mearnsii would be brought under control. We recommend that investment should be made, as a type of insurance for natural capital, in restoring resilience in important water-providing catchments to hedge against future climatic uncertainties.