Climate change impacts on the threatened terrestrial vertebrates of the Pacific Islands

Abstract

Island communities are often regarded as being at the forefront of impacts from environmental hazards, and more so from climate change. Islands are comparatively small in size,are generally remote, highly volatile and with changing geomorphology,lack connectedness and have a high shoreline to land area, hence are particularly vulnerable to climate change related impacts. Smaller islands are much more vulnerable than larger land masses to environmental changes due to the exposure to surrounding oceans, and the flora and fauna found on them are especially vulnerable due to small resource areas and a lack of opportunity to 'migrate' to surrounding areas as climate change has its impacts. While there is a considerable body of research detailing potential climate change related impacts on islands and island communities, there is not much work on climate change related impacts on the flora and fauna found on small island states. Islands are recognised centres of range-restricted species and have high levels of endemism. Information on endemism, species richness and climate change related vulnerabilities are important for the global prioritization of conservation of the affected species, however such information for islands have remained relatively unexplored. More than 20% of the world's biodiversity is found within the 180,000 islands world-wide. Insular endemics found on islands have generally evolved traits such as reduced or loss of dispersal abilities, including loss of flight in birds and insects and a loss of defensive characteristics. Such evolution leads to lower genetic variation and these species are significantly inbred compared to non-endemics. Such characteristics, when combined with the loss of even small amounts of their restricted habitat from climate change related impacts, such as sea level rise, storms and wave action, and the resulting habitat fragmentation makes them highly vulnerable to extinction. Since many of these species are endemic to a few islands only, the extinction of such species from these islands would mean global extinction of those species. The concept of niche width and species diversification seldom applies to the smaller islands as they have limited land area.