Landcover change in mangroves of Fiji: implications for climate change mitigation and adaptation in the Pacific

Abstract Mangrove coverage in Fiji is among the highest of all Pacific island nations. These ecosystems store disproportionate amounts of carbon, provide critically important resources for communities, and protect coastal communities against the impacts of tropical cyclones. They are therefore vital in mitigating and adapting to the impacts of climate change. An improved understanding of both the scale and drivers of mangrove loss in Fiji can underpin sustainable management strategies and achieve climate change mitigation and adaptation goals. In this study we assessed mangrove cover, landcover change, and drivers of landcover change for Fiji between 2001 and 2018, as well as the impacts of landcover change on the structural characteristics of mangroves at selected sites on the Fijian island of Viti Levu. Results were then framed within the context of developing management responses, including the potential to develop forest carbon projects. We found Fiji's mangrove estate to be 65,243 ha, with a loss of 1135 ha between 2001 and 2018 and an annual rate of loss of 0.11%. Tropical cyclones accounted for 77% of loss (~870 ha), with highest losses along the northern coastlines of Viti Levu and Vanua Levu. Mangrove structural characteristics showed high variability in the level of damage incurred, with taller riverine and hinterland vegetation sustaining greater levels of damage than coastal fringing or scrub mangroves. There was no tropical cyclone damage evident along the southern coastline of Viti Levu, with small-scale harvesting the predominate driver of loss in this region. Because of the large effect of cyclone damage on mangroves in the region, small to medium scale restoration projects may be appropriate interventions to increase mangrove cover and carbon stocks. Where harvesting of mangroves occurs, improved management to avoid deforestation could also provide opportunities to maintain mangrove cover and carbon stocks.