biological invasions

Removing wilding conifers (invasive non-native trees in the Pinaceae) has become a major focus of conservation and land management in Aotearoa New Zealand. Management of wilding conifers has been supported by applied research on control methods, generally with a short-term focus of removing or containing invasions to prevent further spread. However, a focus on short-term management activities may not achieve desired longer-term outcomes of restoring economic and environmental values.

Abstract: The Department of Conservation has implemented a Biodiversity and Monitoring Reporting System (BMRS) that estimates occupancy rates and relative abundances of introduced brushtail possums (Trichosurus vulpecula) at a representative sample of sites on public conservation land. Leg-hold traps have been used to monitor possums in the BMRS, but wax tags and chew cards have logistical and financial advantages over traps.

Pinus contorta is a widespread and ecologically damaging invasive tree in the southern hemisphere. Land managers want control methods that limit reinvasion by P. contorta and promote the recovery of native plant communities and ecosystem functions. Recovery of native vegetation may be slow if native seed supply is limited and/or introduced mammals destroy seeds and seedlings. We investigated how tree control method (felling or poisoning), seed addition, and exclusion of introduced mammals affected subsequent seedling establishment in montane stands of invasive P.

Fruit-eating animals play a key role in spreading non-native environmental weeds, via seed ingestion and subsequent dispersal. We reviewed available information on dispersal of fleshy-fruited environmental weeds in New Zealand. We found almost a third (32.9%) of 295 environmental weed species in New Zealand have fleshy fruits adapted for internal dispersal by animals. Fruiting phenology differs between weeds and native plants, with many weed species fruiting from late autumn until early spring (May to September) when native fruits are scarce.

Tiritiri Matangi Island (‘Tiri’) in the Hauraki Gulf of the northern North Island of New Zealand was deforested, pastorally farmed, and then farming was abandoned in 1972. This history is typical of many northern New Zealand islands. The island’s modern history is less typical; since 1984 it has been the focus of a major restoration project involving thousands of volunteers. No original forest remains, but grazed secondary forest in a few valley bottoms covered about 20% of the island when farming was abandoned. Tiri’s wild vascular flora was recorded in the 1900s and again in the 1970s.

Biological invasions have significantly affected New Zealand’s native species and ecosystems. Most prominent are the effects of exotic mammals and plants, whereas few invertebrate invasions are known to have major effects on native ecosystems. Exceptions are the well-known cases of Vespula wasps in Nothofagus forest ecosystems and Eriococcus scale insects in Leptospermum shrublands. This limited impact is surprising because over 2000 exotic invertebrates have become established in New Zealand, among them many pests of exotic crop plants.