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Direct and indirect effects of rats: does rat eradication restore ecosystem functioning of New Zealand seabird islands?
BRB
Available Online

Christa P H Mulder ? M Nicole Grant-Hoffman ? David R Towns ? Peter J Bellingham ? David A Wardle ? Melody S Durrett ? Tadashi Fukami ? Karen I Bonner

Introduced rats (Rattus spp.) can affect island vegetation structure and ecosystem functioning, both directly and indirectly (through the reduction of seabird populations). The extent to which structure and function of islands where rats have been eradicated will converge on uninvaded islands remains unclear. We compared three groups of islands in New Zealand: islands never invaded by rats, islands with rats, and islands on which rats have been controlled. Differences between island groups in soil and leaf chemistry and leaf production were largely explained by burrow densities. Community structure of woody seedlings differed by rat history and burrow density. Plots on islands with high seabird densities had themost non-native plant species. Sincemost impacts of rats were mediated through seabird density, the removal of rats without seabird recolonization is unlikely to result in a reversal of these processes. Even if seabirds return, a novel plant community may emerge.
New Zealand island restoration: seabirds, predators, and the importance of history
BRB
Available Online

Peter J Bellingham ? David R Towns ? Ewen K Cameron ? Joe J Davis ? David A Wardle ? Janet M Wilmshurst ? Christa P H Mulder

New Zealand’s offshore and outlying islands have long been a focus of conservation biology as sites of local endemism and as last refuges for many species. During the c. 730 years since New Zealand has been settled by people, mammalian predators have invaded many islands and caused local and global extinctions. New Zealand has led international efforts in island restoration. By the late 1980s, translocations of threatened birds to predator-free islands were well under way to safeguard against extinction. Non-native herbivores and predators, such as goats and cats, had been eradicated from some islands. A significant development in island restoration in the mid-1980s was the eradication of rats from small forested islands. This eradication technology has been refined and currently at least 65 islands, including large and remote Campbell (11 216 ha) and Raoul (2938 ha) Islands, have been successfully cleared of rats. Many of New Zealand’s offshore islands, especially those without predatory mammals, are home to large numbers of breeding seabirds. Seabirds influence ecosystem processes on islands by enhancing soil fertility and through soil disturbance by burrowing. Predators, especially rats, alter ecosystem processes and cause population reductions or extinctions of native animals and plants. Islands have been promoted as touchstones of a primaeval New Zealand, but we are now increasingly aware that most islands have been substantially modified since human settlement of New Zealand. Archaeological and palaeoecological investigations, together with the acknowledgement that many islands have been important mahinga kai (sources of food) for M?ori, have all led to a better understanding of how people have modified these islands. Restoration technology may have vaulted ahead of our ability to predict the ecosystem consequences of its application on islands. However, research is now being directed to help make better decisions about restoration and management of islands, decisions that take account of island history and key drivers of island ecosystem functioning.
Seabirds enhance coral reef productivity and functioning in the absence of invasive rats
BRB
Available Online

Carr, Peter.

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Graham, Nicholas A. J.

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Hoey, Andrew S.

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Jennings, Simon.

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MacNeil, M. Aaron

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Wilson, Shaun K.

2018
Biotic connectivity between ecosystems can provide major transport of organic matter and nutrients, influencing ecosystem structure and productivity, yet the implications are poorly understood owing to human disruptions of natural flows. When abundant, seabirds feeding in the open ocean transport large quantities of nutrients onto islands, enhancing the productivity of island fauna and flora. Whether leaching of these nutrients back into the sea influences the productivity, structure and functioning of adjacent coral reef ecosystems is not known. Here we address this question using a rare natural experiment in the Chagos Archipelago, in which some islands are rat-infested and others are rat-free. We found that seabird densities and nitrogen deposition rates are 760 and 251 times higher, respectively, on islands where humans have not introduced rats. Consequently, rat-free islands had substantially higher nitrogen stable isotope (?15N) values in soils and shrubs, reflecting pelagic nutrient sources. These higher values of ?15N were also apparent in macroalgae, filter-feeding sponges, turf algae and fish on adjacent coral reefs. Herbivorous damselfish on reefs adjacent to the rat-free islands grew faster, and fish communities had higher biomass across trophic feeding groups, with 48% greater overall biomass. Rates of two critical ecosystem functions, grazing and bioerosion, were 3.2 and 3.8 times higher, respectively, adjacent to rat-free islands. Collectively, these results reveal how rat introductions disrupt nutrient flows among pelagic, island and coral reef ecosystems. Thus, rat eradication on oceanic islands should be a high conservation priority as it is likely to benefit terrestrial ecosystems and enhance coral reef productivity and functioning by restoring seabird-derived nutrient subsidies from large areas of ocean.
Special Issue Article: Tropical rat eradication. Seabird recovery and vegetation dynamics after Norway rat eradication at Tromelin Island, western Indian Ocean. Biological Conservation. Volume 185, May 2015
Island and Ocean Ecosystems, BRB
Available Online

Bastien. M

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Danckwerts. D.K

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M. Le Corre. M

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Micol. T

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Morey Rubio.C

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Orlowski. S

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Pinaud. D

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Ringler. D

2015
Seabirds are notoriously sensitive to introduced mammalian predators and eradication programs have benefitted seabird populations and their habitats on numerous islands throughout the world. However, less evidence is available from the tropics as to the benefits of rat eradication. Here, we report the seabird recovery and vegetation dynamics on a small coralline island of the tropical western Indian Ocean, eight years after Norway rat (Rattus norvegicus) eradication. Two species of seabirds were breeding before rat eradication (red-footed and masked boobies, Sula sula and Sula, dactylatra) and, in both species, the number of breeding pairs had an apparent increase of 22?23% per year after rat eradication. Such a high annual growth rate cannot be achieved by auto-recruitment only and our data suggest that immigration from other source populations never occurred in at least one of these species. We suggest that it is rather due to a rapid increase in breeding success, which rapidly increased the observed number of breeders since birds remained in the available-for-counting-as-breeders group for much longer. Two other species, the white tern (Gygis alba) and the brown booby (Sula leucogaster) were recorded breeding in 2014. The former species has not bred on the island since 1856 and the latter has never bred on the island. Plant cover (monospecific formation of the ruderal herb Boerhavia diffusa) dramatically increased from less than 30% of surface coverage to more than 70%. Although the initial restoration project was to eradicate all introduced mammals of the island simultaneously, house mouse (Mus musculus) eradication failed. Mouse density was high 8 years after rat eradication (32 mice/ha in dry season and 52 mice/ha in rainy season) but not higher than at a comparable tropical island of the region (Juan de Nova) where mice coexist with introduced black rats (Rattus rattus) and feral cats (Felis catus). These results are discussed in terms of the direct positive effects of rat eradication on seabirds and plants and the indirect positive effects of post-eradication seabird increase on soil manuring and vegetation recovery. Overall, our results show that on tropical islands, seabird and habitat recovery can be very rapid after rat eradication and should be implemented as a restoration tool wherever possible.
Special Issue Article: Tropical rat eradication. Trophic roles of black rats and seabird impacts on tropical islands: Mesopredator release or hyperpredation? Biological Conservation. Volume 185, May 2015
Island and Ocean Ecosystems, BRB
Available Online

Le Corre. M.

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Ringler. D

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Russell. J.C

2015
Rats contribute to the decline of tropical seabird populations by affecting their breeding success through direct predation of eggs and chicks. When they coexist with other predators, invasive rats may also generate indirect interactions via the changes they impose on the structure of communities and trophic interactions following invasion (‘hyperpredation process’), or when apex predators are eradicated from the ecosystem (‘mesopredator release effect’). Understanding these effects is necessary to implement restoration operations that actually benefit threatened seabird populations. We investigated these processes on two French tropical seabird islands of the western Indian Ocean, Europa and Juan de Nova, where black rats coexist with two different apex predator species (introduced cats and potentially native barn owls). The parallel use of several methods (diet analysis, stable isotopes, seabird monitoring) to identify trophic roles of rats revealed that the direct impact of rats on seabirds was particularly high on Europa where only rats and owls occur, with high consumption of chicks resulting in low breeding success for several seabird species. We also suggested that hyperpredation associated with top-down regulation of cats is occurring on Juan de Nova, although territoriality of cats may buffer this process. Conversely we found evidence that mesopredator release effect is unlikely, irrespective of the apex predator identity. Considering the most likely effects on both islands we provided recommendations on eradication priorities to mitigate the risk of local extinction that seabirds are currently facing.
SPREP Marine Species Action Plan Review - Proceedings of Meetings 8-14 March, 2012
Island and Ocean Ecosystems
Available Online

SPREP

2012
The review of the SPREP Regional Marine Species Action Plans (MSAP) 2008 – 2012 was conducted from the 8 – 14 March, 2012, at the Hexagon International Hotel, Nadi, Fiji Islands. The SPREP MSAPs are a composite of individual plans for whales and dolphins, marine turtles and dugongs.
Programme régional océanien sur les espèces marines 2013-2017 / Pacific Islands Regional Marine Species Programme
SPREP Publications, Island and Ocean Ecosystems
Available Online

Secretariat of the Pacific Regional Environment Programme (SPREP)

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Secrétariat du Programme régional océanien de l’environnement (PROE)

2013
The Marine Species Programme of the Secretariat of the Pacific Regional Environment Programme (SPREP) outlines a regional strategy for the cooperative conservation and management of dugongs, marine turtles, whales and dolphins. Other marine species of conservation concern will be added as the need arise. The strategy, which will be implemented through Action Plans during 2013–2017, will enable Pacific Islanders to take a primary role in achieving the following vision: A healthy Pacific Ocean with sustainable populations of whales, dolphins, marine turtles, dugongs and other species, and meets the aspirations of Pacific Island peoples and protects their natural and cultural heritage.
Pacific islands regional marine species programme : 2013 - 2017 (action plan) - Dugong, Turtle, Whale and Dolphin
Island and Ocean Ecosystems
Available Online

Secretariat of the Pacific Regional Environment Programme (SPREP)

2012
The Pacific Islands region that is served by SPREP covers 32 million km2 and is in the middle of the largest continuous marine habitat on the planet, the Pacific Ocean. This region is home to a diverse range of large marine animals, including cetaceans (whales and dolphins), sirenians (dugongs), and marine turtles etc. Over half of the world’s known species of cetaceans are found in the region. The area also supports the world’s largest remaining populations of dugongs, and green, hawksbill and loggerhead turtles.
Surveys and capacity building in Kiritimati (Christmas Island, Kiribati) June 2007, to assist in restoration of populations of Bokikokiko and seabirds
Island and Ocean Ecosystems, BRB
Available Online

Ray Pierce , Richard Anderson, Eric VanderWerf and Lindsay Young

2007
Kiritimati (Line Islands, Kiribati) supports globally important populations of many seabird species including the largest breeding populations of two threatened species – Te ruru (Phoenix petrel, Pterodroma alba; Endangered) and Te bwebwe ni marawa (whitethroated storm-petrel, Nesofregetta fuliginosa; Vulnerable). These and other seabirds and one landbird species are increasingly being threated by an increasing human population (5000+) and the impacts of mammalian pests, including the recent arrival of black rats (Rattus rattus).
Review of measures taken by intergovernmental organization to address sea turtle and seabird interactions in marine capture fisheries
Island and Ocean Ecosystems
Available Online

Blanchi, Gabriella

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Gilman Eric

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Moth-Poulsen, Thomas

2007
This document reviews actions taken by intergovernmental organizations (IGOs), including regional fisheries management organizations (RFMOs) and other relevant regional fishery bodies (RFBs), to address problematic sea turtle and seabird interactions in marine capture fisheries. Sea turtles and seabirds are subject to a number of natural and anthropogenic mortality sources, including fishing operations. As a result, all sea turtle species of known status are recognized as being endangered. All sea turtle species excluding the flatback are listed in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which regulates international trade. Of the 61 species of seabirds affected by longline fisheries, 26 are threatened with extinction, including 19 species of albatrosses. The Convention on Migratory Species, which has a broader remit than CITES in terms of its requirements for both domestic and multilateral conservation measures, lists all sea turtles, albatrosses, giant petrels and Procellaria petrels in its Appendices. Due to concern over the status of sea turtles and certain species of seabirds and the possible negative effects of fishing on these populations, several IGOs have taken measures to address these problems. Some of these organizations have begun examining seabird or sea turtle interactions, several have adopted voluntary measures to address problematic interactions, while five RFMOs have legally binding measures requiring the employment of seabird avoidance methods in pelagic and demersal longline and trawl fisheries. There currently are no legally binding measures in place by an IGO to manage turtle-fishery interactions or seabird interactions in coastal gillnet fisheries. Several IGOs, which lack fisheries management authority, serve as advisory mechanisms and conduct cooperative research, or have a primary responsibility of regional sea turtle or seabird conservation.

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