Restoration potential of tropical dry forest on small islands in Fiji
Tropical dry forest is one of the most endangered forest types in the Pacific. It was previously the dominant vegetation of all smaller islands in western Fiji (Yasawa and Mamanuca islands). Of approximately 35 islands in western Fiji, less than half are inhabited but only a handful have any forest remaining.
We examine potential for restoration of dry forest on small islands in Fiji. The island of Yadua Taba (70 ha) is used as a case study as it has some of the best dry forest in Fiji and the only secure population of the critically endangered Fijian crested iguana (Brachylophus vitiensis).
Observations on >20 islands in western Fiji suggest loss of dry forest on uninhabited islands mostly results from the interaction of goat grazing and burning. When burning and intensive grazing ceased on Yadua Taba in 1980, >50% of the island had been converted to grassland and was, or became, invaded by introduced weeds. Between 2002 and 2007 we assessed weed status and trialled control methods for five weed species of concern on Yadua Taba (rain tree, Samanea saman; vaivai, Leucaena leucocephala; trailing daisy, Wedelia trilobata; guava, Psidium guajava; and Lantana, Lantana camara). Given the remoteness of many Fijian islands we used easily-implemented eradication techniques requiring minimal resources.
Two species (rain tree and trailing daisy) appear to prevent native plant regeneration once established. Physical removal of Wedelia and poisoning of rain tree were trialled and appear successful. Impact and success of control of these five species in dry forest may differ to that described for wetter forest types. None of the five species seem to actively invade undisturbed dry forest. Further monitoring is required to determine regeneration potential of Leucaena-infested areas. However, this case study indicates potential for successful restoration of disturbed tropical dry forest after removal of disturbance.