Upper Rantabe Classified Forest is located 90 km south-west of Maroantsetra. The terrain is a succession of mountains and valleys. The Vohilava river flows through the site, as do many permanent or seasonal streams. The vegetation is composed of intact and degraded low-altitude, dense, humid evergreen forest. The canopy layer of intact forest is composed of spur- and stilt-root trees 20–25 m high, dominated by Dalbergia and Tambourissa, while the mid-stratum is dominated by shrubs and abundant tree-ferns Cyathea, and the ground layer is formed of small plants and grasses. Secondary thickets in degraded forest are composed mainly of Solanum and Lantana bushes, and wild ginger Aframomum.
See Box and Tables 2 and 3 for key species. Eighty-two species are known from the site, of which 52 are endemic to Madagascar. All species of the Vangidae family characteristic of wet forests, and species characteristic of low-altitude forests, such as Newtonia fanovanae and Brachypteracias squamigera, are present at the site.