Linking the effects of invasive species to ecosystem services is critical and remains one of the least developed areas in invasion ecology.

The work on costing impacts of alien plant invasions on water resources in South Africa remains the most cited example in the field. Also, the detailed assessment of costs and benefits of the commercially important but invasive tree Acacia mearnsii in South Africa is unique. Where cost/benefit studies of biological control have made elsewhere these have yielded cost:benefit ratios similar to those estimated for South African species, confirming the costeffectiveness of this type of control for extensive invasions and for tackling emerging species. Such information is crucial in strategies to influence the media, and hence politicians and decisionmakers.