NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. The introduced honeybee is abundant and widely but patchily distributed as a feral species across New South Wales. Feral honeybees occur in colonies, usually centered on tree hollows, independently of managed hives that are maintained by beekeepers (Paton 1996). Managed honeybees are not the subject of this determination.
2. There is evidence that honeybees impact on indigenous species in two broad ways, firstly via competition for tree hollows, and secondly via competition for floral resources.
3. Breeding colonies of honeybees occupy large hollows in trees. These hollows are completely taken over by honeybees, and are removed from the pool of hollows available to native species. Due to the long time required for hollow formation [ e.g. 150 years for Blackbutt, Eucalyptus pilularis (Mackowski 1984); Brown Barrel, E. fastigata and Messmate, E. obliqua (Gibbons et al. 2000)] and the long term nature of bee occupation this represents a long term loss of a critical resource. It has been demonstrated that there is some overlap in hollow use between native fauna and feral honey bees (Paton 1996, Wood and Wallis 1998, Soderquist 1999).
4. Due to the physiological characteristics of eucalypt growth, hollow formation is a common trait of this group of plants (Gibbons 1999). Australian fauna, particularly birds and mammals, make extensive use of this structural element of habitat, and at least 20% of bird species (Saunders et al. 1982) are hollow-dependent. All arboreal marsupials use tree hollows, and all except the Koala are dependent upon them for shelter and breeding sites (Lindenmayer et al. 1991). Tree hollows are also used by many species of microchiropteran bats and small scansorial mammals (Dickman 1991, Lumsden and Bennett 2000).
5. Threatened species which are likely to be affected by competition from honeybees for hollows include the Brush-tailed Phascogale, Phascogale tapoatafa; Squirrel Glider, Petaurus norfolcensis; Yellow-bellied Glider, Petaurus australis; Major Mitchell's Cockatoo, Cacatua leadbeateri; Glossy Black Cockatoo, Calyptorhynchus lathami; Superb Parrot, Polytelis swainsonii; and Regent Parrot, Polytelis anthopeplus. Populations of protected species that may become threatened include the Common Brushtail Possum, Trichosurus vulpecula; Greater Glider Petauroides volans; and Sugar Glider, Petaurus breviceps (Garnett 1992, Oldroyd et al. 1994, Paton 1996, Soderquist et al. 1996, Trainor 1995, Wood and Wallis 1998, Pyke 1999, Soderquist 1999).
6. Honeybees, both feral and managed, are frequent visitors at flowers, and often remove 80% or more of the floral resources produced (Paton 1996, 2000). This can result in competitive displacement of native fauna that use the floral resources, including honeyeaters (Paton 1993) and native bees (Sugden and Pyke 1991, Paton 1996, Sugden et al. 1996, Schwarz and Hurst 1997, cf. Spessa 1999).
7. Removal of pollen by honeybees has been shown to affect seed set in several plant species. Seed set is reduced in Melastoma affine (Gross and Mackay 1998), and Grevillea macleayana (Vaughton 1996, Whelan et al. 2000, Richardson et al. 2000). Feral honeybees may also reduce seed set in species of Persoonia due to inefficient transfer of pollen (Bernhardt and Weston 1996). Honeybees can have neutral or beneficial effects on some Banksia species, although these effects may become manifest only after honeybees have depleted populations of native pollinators (Paton 1997, 2000).
8. Evidence from studies in Europe, where honeybees are native, and from other parts of the world where honeybees have been introduced, suggests that several factors interact to determine the magnitude of impact of the bees on native flora and fauna. These factors include the degree of habitat fragmentation and disturbance, the extent of temporal and spatial overlap in use of floral resources, and the presence of other introduced species that can facilitate honeybee presence (Butz Huryn 1997, Kato et al. 1999, Schwarz and Hogendoorn 1999, Steffan-Dewenter and Tscharntke 2000, Barthell et al. 2001, Roubik and Wolda 2001). For these reasons, further research to predict taxa most at risk from competition from feral honeybees should be an objective of a future Threat Abatement Plan.
9. In view of the above points, the Scientific Committee is of the view that Competition from feral honeybees Apis mellifera L. could cause species that are not threatened to become threatened. Consequently, this process is eligible to be listed as a Key Threatening Process in Schedule 3 of the Act.
Proposed Gazettal date: 29/11/02
Exhibition period: 29/11/02 - 17/01/03
References
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