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Since Elton highlighted the problem of biological invasions, numerous studies have established their importance in the structural evolution of natural communities, in particular insular communities. Because of their isolation, islands are regarded as natural evolution laboratories which are characteristically very fragile once the boundary is disturbed. This fragility is illustrated by the high proportion of species extinctions observed in islands: since 1600, more than 75% of monitored disappearances have been registered in islands. Invasions are not an abnormality in the evolutionary process, but an increase in their rate could lead to a dramatic homogenization of fauna and flora.

Verbesina encelioides (Cav.) Benth. & Hook. f. ex A. Gray, golden crownbeard, is a sunflower-like herbaceous annual plant ranging in height from 0.3 to 1.7 m with showy yellow flowers. It is native to the southwestern United States, the Mexican Plateau, and other parts of tropical America. Its invasive characteristics include high seed production (as many as 300-350 seeds per flower and multiple flowers per plant), seed dormancy, ability to tolerate dry conditions, and possible allelopathic effects. Disturbed areas with a relatively sandy substrate within warm, arid climate zones are vulnerable to invasion by V. encelioides. Veresina encelioides is found on all of the main Hawaiian islands except Ni'ihau but is particularly problematic on Midway and Kure Atoll, where it may threaten the habitat of nesting birds such as Laysan and black-footed albatrosses and Christmas and wedge-tailed shearwaters. Many other Pacific islands with similar habitats could be invaded by the V. encelioides. The plant has become naturalised in many other U.S. states, parts of South America, the Bahamas, Cuba, the Dominican Republic Puerto Rico, parts of Europe, Saudi Arabia, India, Ethiopia, Morocco, Botswana, Namibia, Israel, and Australia. It is a pest of various crops in the southern United States and India and is poisonous to sheep and cattle. Verbesina encelioides can be controlled via herbicides or mechanical means, but measures must be repeated due to the presence of persistent seed banks. Further research on V. encelioides is needed to understand its population dynamics, allelopathic properties, and impacts on natural ecosystems.

Mangrove ecosystems are threatened by climate change. We review the state of knowledge of mangrove vulnerability and responses to predicted climate change and consider adaptation options. Based on available evidence, of all the climate change outcomes, relative sea-level rise may be the greatest threat to mangroves. Most mangrove sediment surface elevations are not keeping pace with sea-level rise, although longer term studies from a larger number of regions are needed. Rising sea-level will have the greatest impact on mangroves experiencing net lowering in sediment elevation, where there is limited area for landward migration. The Pacific Islands mangroves have been demonstrated to be at high risk of substantial reductions. There is less certainty over other climate change outcomes and mangrove responses. More research is needed on assessment methods and standard indicators of change in response to effects from climate change, while regional monitoring networks are needed to observe these responses to enable educated adaptation. Adaptation measures can offset anticipated mangrove losses and improve resistance and resilience to climate change. Coastal planning can adapt to facilitate mangrove migration with sea-level rise. Management of activities within the catchment that affect long-term trends in the mangrove sediment elevation, better management of other stressors on mangroves, rehabilitation of degraded mangrove areas, and increases in systems of strategically designed protected area networks that include mangroves and functionally linked ecosystems through representation, replication and refugia, are additional adaptation options.

Coupled human-environmental timelines are used to explore the temporal coevolution of driving forces and adaptive strategies from the 1960s to 2006 on Bellona in the SW Pacific. Climatic events and agro-environmental conditions are assessed in conjunction with issues such as population dynamics, agricultural strategies, non-agricultural activities, transport and infrastructure, migration, education, political conditions, etc. Satellite imagery and aerial photos reveal relative stability in agricultural land use intensity despite an increase in de facto population (51% from 1966-2006). Results of questionnaire survey of 48 households show that the utilization of natural resources (notably shifting cultivation and fisheries) remains wide-spread, although it is increasingly supplemented by other income generating activities (eg. shopkeeping, private business, government employment). Group interviews are used to discuss ways in which the local communities' adaptive resource management strategies have been employed in the face of climatic and socioeconomic events and changes in the recent past. Fifty years' development is described as a combination of continuity and change. Resource management practices are only marginally impacted by different stress factors, but the importance of agriculture has been decreasing in relative terms. Culturally determined bonds have become a main 'mechanism' to cope with environmental or socioeconomic stress and the Bellonese have become less vulnerable to external shocks.

The prevalence of bleaching was recorded in staghorn thickets of two back reef pools on a biweekly basis during the October to June bleaching season, and monthly basis for the rest of the year at Tutuila, American Samoa. Recording began in late 2003 and has continued since, and used a rapid visual estimation procedure. Three species of staghorns (Acropora spp.) in both pools bleached every Austral summer for five years. Reports of reef slope bleaching events in 2002 and 2003 imply that they bleached in those years as well. Thus, these corals have bleached for at least five summers and likely seven summers or more in a row. Other, less common species of Acropora and Millepora were observed to bleach as well. The bleaching displayed patterns consistent with the view that both temperature and irradiance are involved in producing the bleaching. The term “photothermal bleaching” was applied to this type of bleaching. This appears to be the first annual multi-species summer bleaching event reported.

It is widely recognized that trophic interactions structure ecological communities, but their effects are usually only demonstrated on a small scale. As a result, landscape-level documentations of trophic cascades that alter entire communities are scarce. Islands invaded by animals provide natural experiment opportunities both to measure general trophic effects across large spatial scales and to etermine the trophic roles of invasive species within native ecosystems. Studies addressing the trophic interactions of invasive species most often focus on their direct effects. To investigate both the presence of a landscape-level trophic cascade and the direct and indirect effects of an invasive species, we examined the impacts of Norway rats (Rattus norvegicus) introduced to the Aleutian Islands on marine bird densities and marine rocky intertidal community structures through surveys conducted on invaded and rat-free islands throughout the entire 1,900-km archipelago. Densities of birds that forage in the intertidal were higher on islands without rats. Marine intertidal invertebrates were more abundant on islands with rats, whereas fleshy algal cover was reduced. Our results demonstrate that invasive rats directly reduce bird densities through predation and significantly affect invertebrate and marine algal abundance in the rocky intertidal indirectly via a cross-community trophic cascade, unexpectedly changing the intertidal community structure from an algae- to an invertebrate-dominated system.

Breeding success of 5 Cory’s shearwater Calonectris diomedea sub-colonies of Lavezzu Island (Lavezzi Archipelago, Corsica) was checked annually for 25 consecutive years from 1979 to 2004. Between 1989 and 1994, 4 ship rat Rattus rattus controls were performed in several subcolonies. In November 2000, rats were eradicated from Lavezzu Island and its 16 peripheral islets (85 ha) using traps then toxic baits. We compare cost (number of person-hours required in the field) and benefit (Cory’s shearwater breeding success) of control and eradication. The average breeding success doubled when rats were controlled or eradicated (0.82) compared to the situation without rat management (0.45). Moreover, the average breeding success after eradication (0.86) was significantly (11%) higher than after rat controls (0.75). Furthermore, the great variation in breeding success recorded among sub-colonies both with and without rat control declined dramatically after eradication, suggesting that rats had a major impact on breeding success. The estimated effort needed to perform eradication and checking of the permanent bait-station system during the year following eradication was 1360 person-hours. In contrast, rat control was estimated to require 240 or 1440 person-hours per year when implemented by trained and untrained staff, respectively. Within 6 yr, eradication cost is lower than control cost performed by untrained staff and confers several ecological advantages on more ecosystem components than Cory’s shearwater alone. Improved eradication tools such as hand or aerial broadcasting of toxic baits instead of the fairly labour-intensive eradication strategy we used would dramatically increase the economic advantage of eradication vs. control. Therefore, when feasible, we recommend eradication rather than control of non-native rat populations. Nevertheless, control remains a useful management tool when eradication is not practicable.

This article is a study on the dietary shift of black rats on Surprise Island, New Caledonia and their impact on the ecosystem in the presence and absence of breeding seabirds.