Climatic changes at Coringa-Herald National Nature Reserve (CHNNR) in the last 82 yr include a 0.7°C rise in mean minimum winter temperatures and increases in drought duration and frequency. Between 1991 and 2002, a plague of the scale insects Pulvinaria urbicola (Cockerell), together with attendant ants destroyed Pisonia grandis R.Br, rain forest at South-West Coringa Islet. Scale insect damage of P. grandis has also been recorded at North-East Herald Cay. This study explored the reasons for vegetation dieback during current climate. Woody species such as Argusia argentea (L.) Heine, Cordia subcordata Lam., and the grasses Lepturus repens (G. Forst.) R.Br. and Stenotaphrum micranthum (Desv.) C. E. Hubb. have also declined at CHNNR. Ximenia americana L. and Digitaria ctenantha (F. Muell.) Hughes were found to be locally extinct. Dieback of forests results in reduction of canopy-breeding seabirds and burrowing shearwaters (Puffinus pacifiais [Gmelin)]. Dieback species were replaced by the shrub Abutilon albescens Miq. and/or fleshy herbaceous plants such as Achyranthes aspera L., Boerhavia albiflora Fosberg, Ipomoea micrantha Roem. & Schult, Portulaca oleracea L., and Tribulus cistoides L. Increasing duration of droughts and increased temperatures, together with damage caused by exotic insect pests, appear to be the key drivers of the current vegetation changes.