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Threats to mangroves from climate change and adaptation options
Climate Change Resilience, Biodiversity Conservation
Available Online

Duke Norman C

,

Ellison Joanna

,

Field Colin

,

Gilman, Eric L

2008
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.
Conservation of kakerori (Pomarea dimidiata) in the Cook Islands in 2006/07
BRB
Available Online

Robertson Hugh a.

,

Saul. Edward K.

2008
In 1989, the kakerori (Pomarea dimidiata) was one of the 10 rarest birds in the world with a declining population of just 29 individuals living in forested hill country in the Takitumu Conservation Area (TCA) of south-eastern Rarotonga, Cook Islands. Following 12 years of rat poisoning, the population had increased to 255 birds in August 2001. The programme then shifted from ‘species recovery’ to ‘sustainable management’ of the Rarotonga population at 250 to 300 birds. The rat poisoning effort was reduced, and an ‘insurance’ population was established on Atiu. By August 2004, following the reduction of poisoning from weekly to fortnightly, and the transfer of 30 youngsters to Atiu in 2001–03, there were 281 birds on Rarotonga and 25 on Atiu. The southern Cook Islands were hit by five tropical cyclones in a four-week period in February–March 2005, and forests on Rarotonga were severely damaged. Kakerori survived the storms remarkably well, but the main effect was observed in the following breeding season (2005/06), when nesting success on Rarotonga was exceptionally poor. Reduced canopy cover caused nests to be exposed to abnormally wet conditions, and lack of fruit meant that rats were exceptionally hungry. Only 31 yearlings were known to be alive in August 2006—about half the expected number—and annual mortality of banded birds (25%) was the highest since management began. The kakerori population on Rarotonga fell 8% from 275 birds in August 2005 to a minimum of 254 birds in August 2006. The situation was better on Atiu, with the population growing from about 32 adult birds in 2005/06 to a minimum of 37 adult birds in 2006/07, and an Atiu-bred pair nested successfully for the first time. The 2006/07 breeding season on Rarotonga was moderately successful, with a minimum of 51 fledglings found. Because the ‘sustainable management’ regime of fortnightly rat poisoning in the TCA was only just adequate in giving protection to adult kakerori, the annual poisoning programme was modified by adding rounds of ‘interim’ poisoning in April and July 2007 aimed at reducing rat and cat numbers before the breeding season.