Ecological Restoration of sub-Antarctic Macquarie Island

Springer, K. Ecological Restoration of sub-Antarctic Macquarie Island.

Invasive vertebrate species have had devastating impacts on the flora, fauna and landforms of Macquarie Island over a period of 200 years. Following the successful eradication of weka (Gallirallus australis) by 1989 and feral cats (Felis catus) by 2001, planning for the eradication of ship rats (Rattus rattus), house mice (Mus musculus) and European rabbits (Oryctolagus cuniculus) began in 2004. Funding of AUD$24.7M was secured in 2007 for a multi-year project based on aerial baiting targeting rabbits and rodents followed by ground hunting targeting surviving rabbits. The first aerial baiting attempt in 2010 was abandoned due to unfavourable weather and shipping delays. The degree of non-target seabird species mortality from limited baiting in 2010 lead to a renewed examination of non-target mitigation options. Rabbit Haemorrhagic Disease Virus (RHDV) was introduced in February 2011, to reduce the pre-baiting rabbit population and thus minimise non-target mortality amongst scavenging seabirds. Aerial baiting resumed in May 2011 using four AS350 helicopters and a team of 27 people, and was completed by July 2011. No rodents have been detected post-baiting and the estimated rabbit population of 150,000 has been reduced to fewer than 30 at the conclusion of baiting The rabbit hunting phase commenced in July 2011 using a team of 15 hunters and 12 dogs and is ongoing, with thirteen rabbits accounted for. Hunting and monitoring is expected to take a total of five years post-baiting and will be based on annual progress reviews. A minimum of two years monitoring will be conducted. Rodent detection dogs will deploy in 2013 to assist in determining rodent eradication success.
Six months after baiting, vegetation recovery was already evident and increased burrownesting seabird activity has also been observed in the first breeding season post-baiting.

Increase in seabirds and changes in soil nutrients after removal of feral predators and alien plants

VanderWerf, E. A., Young, L. C., Crow, S. E., Opie, E., Yamazaki, H., Miller, C. J., Anderson, D.G., Brown, L.S., Smith D.G. & Eijzenga, J. (2014). Increase in Wedge‐tailed Shearwaters and Changes in Soil Nutrients following Removal of Alien Mammalian Predators and Nitrogen‐fixing Plants at Kaena Point, Hawaii. Restoration Ecology.

A predator-proof fence was built at Kaena Point Natural Area Reserve, Hawaii in 2010 as part of an ecosystem restoration project. All non-native mammalian predators were removed and are now excluded. Non-native plants are being removed and native species are being outplanted. We monitored abundance and reproduction of Puffinus pacificus (wedge-tailed shearwaters), collected soil samples before and after fence construction, and examined the relationship between changes in shearwater numbers and soil nutrients. Shearwater numbers increased over time, from 11 young produced in 1994 to 3,274 in 2012. The average number of shearwaters produced during the 3 years before and after fence construction increased from 614 ± 249 to 2,359 ± 802 (384% increase). The average number of shearwater pairs attempting to nest also increased during the same periods, from 3,265 ± 827 to 4,726 ± 826 (45% increase). Soil samples from 2010 to 2013 showed an overall decline in concentration of ammonium (NH₄⁺) and no change in concentration of nitrate (NO₃⁻) or orthophosphate (PO₄³⁻). . However, there was a positive relationship between changes in shearwater numbers and changes in ammonium. Examination of spatial patterns in nutrient abundance showed that the highest nutrient concentrations occurred in areas dominated by the non-native nitrogen-fixing plants Leucaena leucocephala and Prosopis pallida. Removal of these plants caused local nutrient declines, but increases in shearwater numbers have countered this at some points. We anticipate that shearwaters and other seabirds will replace non-native plants as the dominant source of nitrogen and phosphorous and facilitate recovery of a native-dominated plant assemblage.

Ecological restoration on Macquarie island

Copson, G., & Whinam, J. (2001). Review of ecological restoration programme on subantarctic Macquarie Island: pest management progress and future directions. Ecological Management & Restoration, 2(2), 129-138.
The establishment of exotic species of vascular flora and vertebrate fauna on subantarctic Macquarie Island since its discovery in 1810 has resulted in major changes in the biota. A management programme aims to reduce the numbers of exotic plant and animal species and assist with the recovery of pre-existing communities and processes. This paper reviews the integrated vertebrate pests management programme on Macquarie Island since 1974 and outlines future management considerations. As part of this programme, the responses of some native and exotic species of vascular flora and vertebrate fauna were monitored following control of European Rabbit (Oryctolagus cuniculus) numbers. Changes in the vegetation recorded over 10 years showed that approximately half of all the vascular species had benefited from rabbit grazing, including several which formed a major part of the rabbit’s diet. After rabbit control, some adversely affected plants responded rapidly to a reduction in grazing pressure while others will require an almost total cessation of grazing in order to re-establish their former distributions. With the decrease in rabbit numbers it was also necessary to control Feral Cats (Felis catus) due to their increased predation on native burrow-nesting birds. Feral Cat predation on introduced fauna also increased, one result of which was the eradication from the island of the introduced Weka (Gallirallus australis scotti). Reduced rabbit grazing is leading to re-establishment of the native Tall Tussock (Poa foliosa) grassland and with it the spread of the introduced Ship Rat (Rattus rattus). This review indicates that an integrated approach to pest management, with monitoring of the responses of both target and non-target species, is the most effective way to restore pre-existing communities and processes.

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