Open Access

Petrus C. Heyligers, Laurie G. Adams

• Montagu Island (36°15’S; 150°14’E) is situated about 10 km east of Narooma on the New South Wales South Coast. The paper presents evidence about the changes in the terrestrial vegetation of the island since it was first seen by Europeans, provides a floristic inventory and gives a perspective on the effects of introduced species. Flinders (1814) mentions that the island "produced small trees." This is the only record of what grew on the island until in 1880 annotations on a map, made at the time of the construction of the lighthouse, mentioned the presence of scrub, trees and rank grass. This is confirmed by photographic evidence, but by 1932, when the botanist F. A. Rodway visited the island, the trees had disappeared. In 1973, during a land use survey of the South Coast, a team of CSIRO described the vegetation as a distinct series of dune communities belonging to the Lomandra longifolia – Pteridium esculentum – Phragmites australis complex. Vegetation mapping in the late 1980s confirmed the prevalence of these species, except that Pennisetum clandestinum then covered a large area along the west side of the island. Excluding taxa used for ornamental or culinary purposes, nearly 200 species of vascular plants have been recorded since 1932 of which about 140 were still present in the late 1990s. There are ten species of ferns e.g. Pteridium esculentum, widespread and sometimes codominant with Lomandra longifolia, and Asplenium obtusatum, frequently found among the rocks along the east side of the island. The only taxon unique to Montagu Island is a hybrid of this species and Asplenium australasicum. Among the flowering plants there are about 110 native species and about 70 species naturalised in Australia. About 85 and 40, respectively, are still present today. Many of these have a wide distribution in Australia and only about 25 have a more restricted coastal distribution. The species that have disappeared include many that were weeds in the vegetable gardens or around the chicken sheds. Several naturalised species still present are notorious for their capacity to overrun existing vegetation. Foremost among these is Pennisetum clandestinum, which now covers about one-third of the island; Acetosa sagittata is a close second. Other contenders are Dipogon lignosus and Delairea odorata. It is now apparent that these species were kept in check by the feral goats that roamed the island before it was declared a Nature Reserve in December 1987.