Alien invasions: gauging the costs to manage them

The costs of managing invasive alien species and their impacts are not well understood in the Pacific. IUCN Member, Landcare Research, recently completed a first-of-its-kind economic survey of the impacts of five key invasive species in eastern Viti Levu, Fiji’s main island.

The survey covered 30 villages in eastern Viti Levu.

Invasive species pose an enormous threat in the Pacific: not only do they strongly affect biodiversity, but they also potentially affect the economic, social, and cultural wellbeing of Pacific people.

Speaking at a lecture organized by IUCN Oceania yesterday, Pike Brown and Adam Daigneault, economists from Landcare Research, elaborated on the surveys and their findings.

Brown and Daigneault found that the most cost-effective management option varies by species, precluding a universal solution. Nevertheless, the benefits of management often exceed the costs of management by a wide margin, arguing for a more concerted effort to control the spread of invasive species in the Pacific.

They looked at Spathodea campanulata (African tulip tree), Herpestus javanicus (small Asian mongoose), Papuana uninodis (taro beetle), Pycnonotus cafer (red-vented bulbul), and Merremia peltata (merremia vine).

The African tulip tree and taro beetle were found to be the worst invasives, both in terms of their popular perceptions and their economic impacts. In both cases, the benefits of managing these species far outweighed the costs of doing so.

Brown says that for the African tulip tree, an integrated approach is recommended; for the taro beetle, chemical spraying is most cost effective.

Importantly, villagers reported being willing to donate significant amounts of their own time to control if proven methods are available,” says Daigneault.

The mongoose, red-vented bulbul, and merremia vine were estimated to have much lower impacts on village livelihoods. Survey respondents believed that the mongoose should be controlled, and the benefits of control – whether through trapping or hunting – exceed the costs.

For merremia vine and the red-vented bulbul, Brown and Daigneault note that the economic motivations for control are small, and thus that it may be difficult for governments to prioritise management of these species; that being said, the gains to controlling merremia and red-vented bulbul may be significant from the perspective of promoting biodiversity.

Their analysis was informed by extensive survey data on the incidence, management, and impacts of the five species in Fiji.

Together with colleagues from the Institute of Applied Sciences at the University of the South Pacific and Nature Fiji-Mareqeti Viti, Brown and Daigneault surveyed 476 households, 359 of these in 30 villages in eastern Viti Levu.

The village and community surveys provided the first-ever quantification of the socio-economic impacts of invasive species in eastern Viti Levu.

"Information from this survey will be important for biosecurity purposes and also for conservation practitioners because there is very little knowledge on cost-benefit analysis of invasive species in the published space," says Daigneault.

The African tulip tree, the small Asian mongoose and the Red-vented Bulbul are listed on IUCN's 100 of the World's Worst Invasive Alien Species.

For more information on this research contact Pike Brown,, and Adam Daigneault


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