Are We Destroying Our Insurance Policy? The Effects of Alien Invasion and Subsequent Restoration - Landscape Ecology for Sustainable Environment and Culture - page 325

Chapter 16
Are We Destroying Our Insurance Policy?
The Effects of Alien Invasion
and Subsequent Restoration
A Case Study of the Kromme River System, South Africa
Alanna J. Rebelo, David le Maitre, Karen J. Esler
and Richard M. Cowling
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 agri-
culture 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-pro-
viding catchments to hedge against future climatic uncertainties.
Keywords Floodplain wetlands Ecosystem goods and services Degradation
Restoration Prionium serratum Land-cover change Climate change