Forest Plant and Bird Communities in the Lau Group, Fiji

Abstract

BackgroundWe examined species composition of forest and bird communities in relation to environmental and human disturbance gradients on Lakeba (55.9 km2), Nayau (18.4 km2), and Aiwa Levu (1.2 km2), islands in the Lau Group of Fiji, West Polynesia. The unique avifauna of West Polynesia (Fiji, Tonga, Samoa) has been subjected to prehistoric human-caused extinctions but little was previously known about this topic in the Lau Group. We expected that the degree of human disturbance would be a strong determinant of tree species composition and habitat quality for surviving landbirds, while island area would be unrelated to bird diversity.Methodology/Principal FindingsAll trees >5 cm diameter were measured and identified in 23 forest plots of 500 m2 each. We recognized four forest species assemblages differentiated by composition and structure: coastal forest, dominated by widely distributed species, and three forest types with differences related more to disturbance history (stages of secondary succession following clearing or selective logging) than to environmental gradients (elevation, slope, rockiness). Our point counts (73 locations in 1 or 2 seasons) recorded 18 of the 24 species of landbirds that exist on the three islands. The relative abundance and species richness of birds were greatest in the forested habitats least disturbed by people. These differences were due mostly to increased numbers of columbid frugivores and passerine insectivores in forests on Lakeba and Aiwa Levu. Considering only forested habitats, the relative abundance and species richness of birds were greater on the small but completely forested (and uninhabited) island of Aiwa Levu than on the much larger island of Lakeba.Conclusions/SignificanceForest disturbance history is more important than island area in structuring both tree and landbird communities on remote Pacific islands. Even very small islands may be suitable for conservation reserves if they are protected from human disturbance.

The Effect of the Small Indian Mongoose (Urva auropunctatus), Island Quality and Habitat on the Distribution of Native and Endemic Birds on Small Islands within Fiji

“…These species are primarily frugivores, nectivores and insectivores requiring good canopy cover. Forest ecosystems require such species to provide services for the pollination and dispersal of plant propagules [65]; on some islands (Dravuni, Macuata-i-wai, Malake, Nananu-i-ra, and Yanuca) little natural vegetation remains intact and the islands are highly modified talasiga communities [43] which would severely limit the viability of such species.…”

“…Furthermore, this must involve local community participation as this approach is the only one likely to succeed in the long term. Conserving quality habitat is a key factor when trying to preserve avifauna in Fiji, and elsewhere in the Pacific [7], [8], [43]. The development of community-led strategies to protect and enhance the remaining native forests could successfully preserve these important natural resources.…”

“…Fiji has nine principal vegetation types; lowland rainforest, upland rainforest, cloud forest, mangrove forest and scrub, plant communities degraded by fire ( talasiga ), coastal strand vegetation, freshwater wetland vegetation and smaller island vegetation [47]. The latter refers to lowland rain forests where the species richness of the canopy trees has been highly modified by people [43].…”

“…Although some bird work has been done on Fiji's outer islands the majority was completed over 80 years ago [37]–[43] or remains unpublished [44]. Yet these islands have populations of native species that are particularly vulnerable to extinction.…”

Resource extractivism, health and climate change in small islands

“…This lack of manufacturing or value-adding to gain economic benefit from resource depletion is common in small islands with limited capacity for manufacture (including skilled labor, infrastructure, regulations), with only a few countries, such as Vanuatu and Fiji, having developed small-scale local industry associated with forestry (Australian Centre for International Agircultural Research, 2012). Unregulated logging creates local environmental problems such as erosion and increased landslide risk, and with loss of primary forest, loss of biodiversity (Franklin and Steadman, 2010) and invasion of pest species, including exotic Climate change in small islands grasses that make forest re-generation more difficult (Denslow et al, 2006). Further, like with fossil fuels (below), forest loss also contributes to climate change through the removal of carbon sinks and directly to carbon emissions if the wood is then burned.…”