This site lies c.10 km from Sakaraha and 130 km from Toliara, and consists of the Zombitse, Vohibasia and Isoky-Vohimena Forests, which cover a gently undulating terrain of dome-shaped sandstone hills. The Isalo massif lies to the east, and a calcareous plateau (820 m high) to the west—both are oriented north–south. The soil is sandy. The Fiherenana and Teheza rivers, tributaries of the Onilahy, rise within the Zombitse and Vohibasia Forests. The vegetation consists of dense deciduous forest and xerophilous bushland, dominated by Securinega, Malleastrum, Carissa and Teclea, with some emergents, such as Commiphora and Brachylaena. The xerophilous bushland is characterized by species of Euphorbia, Adansonia and Dialium.
See Box and Tables 2 and 3 for key species. Ninety species are known from this site, of which 38 are endemic to Madagascar. One of the endemic species, Phyllastrephus apperti, is known only from the forests of Zombitse and Analavelona (IBA MG066). Two species, Thamnornis chloropetoides and Nesillas lantzii, are characteristic of spiny forest. Monticola bensoni is recorded here seasonally.
The park is a biological reservoir of primary importance, due to its location straddling the western and southern domains of Madagascar. Route Nationale 7 runs through Zombitse Forest. The main threats include exploitation of forest species, cattle-grazing, vegetation clearance and deforestation for maize cultivation or production of charcoal, as well as uncontrolled bush-fires.