Australian acacia species in New Zealand: introduction, invasibility and impact.
- Author
- Hulme PE
- Year
- 2023
- Journal / Source
- in: Wattles: Australian Acacia Species Around the World. Ed Richardson DM, Le Roux JL, Marchante EM
- Publisher / Organisation
- GB: CABI
- Pages
- 216-230
- Summary
- Species of the genus Acacia (‘wattles’) were once native to New Zealand but became extinct in the Pleistocene. European settlers reintroduced wattles 90,000 years later, initially for utilitarian purposes such as for tannin production or timber and later for ornament. Today, at least 150 Acacia species have been deliberately introduced into New Zealand from Australia. Of these, less than 10% have subsequently become naturalized, several soon after widespread planting in the 19th century. Most naturalized species have origins in south-eastern Australia, the native region with the closest climate match to New Zealand. Although most naturalized wattles have been classed as environmental weeds and targeted for management in one or more protected areas, only four species are the subject of regional regulations prohibiting their sale or dissemination. Quantitative evidence of the scale of their impacts on biodiversity or ecosystem functions is lacking. Wattles are largely found in ruderal or early successional habitats where they are expected to be outcompeted by native forest vegetation at the time of canopy closure. Wattles are thus primarily viewed as a risk in habitats of naturally low vegetation stature. The absence of widespread invasion reflects the fact that many natural enemies have been unintentionally introduced from Australia to New Zealand, including several phytophagous and seed-feeding insects as well as wattle-specific fungal pathogens. The latter have had a significant impact in limiting the commercial exploitation of certain wattle species and thus can also be expected to constrain invasion. At present, wattles pose localized problems rather than a widespread threat to New Zealand’s environment. However, increasing interest in further use of species in silvopastoral systems, as bioenergy feedstocks or carbon forests could increase propagule pressure to the extent that further invasive spread is likely. More comprehensive data on impacts will be required to ensure future economic developments do not come at the costs of biodiversity.