This site consists of an arc of hills and a series of forests along the western rim of Tzaneen. The landscape comprises spectacular mountains with steep slopes, gorges and amphitheatres. Rainfall averages 500 mm p.a. on the lower slopes, but as much as 1 500 mm p.a. can fall in the high-altitude mist-belt. Annual average minimum and maximum temperatures are 7 °C and 21 °C respectively, but variations in altitude result in temperatures ranging between -1 °C and 33 °C.
The IBA includes a number of forest reserves. Although the region is dominated by a matrix of Eucalyptus and Pinus plantations, large expanses of good-quality, high-altitude Afromontane forest and small patches of grassland are scattered in the valleys and moist basins of the Tzaneen Mountains. There are distinct strata of emergent, canopy and shrub layers in the forest, and trees can reach a height of 50 m.
Several important rivers have their sources in these mountains, including the Molototsi, Nwandi, Hlangana and Letsitele, most of which eventually empty into the Letaba River. The Letaba, which flows into the Kruger National Park and neighbouring Mozambique, periodically runs dry due to the loss of catchment water from the water-hungry plantations. Water conservation is a high priority issue on the escarpment, and water utilisation requires intense monitoring and management.
Bat Hawk Macheiramphus alcinus breeds in plantations and forest reserves in the IBA, as do both Martial Eagle Polemaetus bellicosus and Crowned Eagle Stephanoaetus coronatus. Peregrine Falcon Falco peregrinus occurs on the mountain cliffs. This is one of very few areas in South Africa holding Black-fronted Bush-Shrike Chlorophoneus nigrifrons, which inhabits forest and forest edges. The region's forests are also home to Cape Parrot Poicephalus robustus, Orange Ground Thrush Zoothera gurneyi, Bush Blackcap Lioptilus nigricapillus, Forest Buzzard Buteo trizonatus, Knysna Turaco Tauraco corythaix, Chorister Robin-Chat Cossypha dichroa, Brown Scrub Robin Erythropygia signata, Grey Cuckooshrike Coracina caesia, Olive Bush-Shrike Chlorophoneus olivaceus, Green Twinspot Mandingoa nitidula and Forest Canary Serinus scotops.
Some of the local rivers, particularly those at lower altitude, hold African Finfoot Podica senegalensis and White-backed Night Heron Gorsachius leuconotus. Marshy and open climax grasslands support Broad-tailed Warbler Schoenicola brevirostris and Striped Flufftail Sarothrura affinis. Blue Swallow Hirundo atrocaerulea has been recorded and probably regularly uses these grasslands on migration.
Globally threatened species are Bush Blackcap and Crowned Eagle. Regionally threatened species are White-backed Night Heron, Striped Flufftail, African Finfoot, Cape Parrot, Half-collared Kingfisher Alcedo semitorquata, Bat Hawk and Orange Ground Thrush. The restricted-range and biome-restricted species in the IBA are Knysna Turaco, Grey-headed Bush-Shrike Malaconotus blanchoti, White-starred Robin Pogonocichla stellata, Yellow-throated Woodland Warbler Phylloscopus ruficapilla, White-bellied Sunbird Cinnyris talatala, Swee Waxbill Coccopygia melanotis and Forest Canary Crithagra scotops, which are common. Fairly common species in these categories are Forest Buzzard, Orange Ground Thrush and Brown Scrub Robin, while Barratt's Warbler Bradypterus barratti is an uncommon species.
The extremely rare and localised Wolkberg cycad Encephalartos dolomiticus, which grows only on dolomite and in the vicinity of Penge, almost certainly occurs in the IBA; its global range is restricted to the Wolkberg. A large population (1 000 individuals) of the slightly more widespread Modjadji cycad E. transvenosus is found in the Lekgalameetse Nature Reserve. Several other range-restricted plants grow in the IBA, including Euphorbia restricta, Cyrtanthus thornicroftii, Kniphofia coralligemma, Encephalartos eugenemaraisii and E. inopus. They are all endemic to the Mpumalanga–Limpopo Province escarpment.
A subspecies of the range-restricted Transvaal rain frog Breviceps sylvestris sylvestris is endemic to the Wolkberg. Three reptile species have global ranges restricted to this IBA: Woodbush flat gecko Afroedura multiporis and the threatened Methuen's dwarf gecko Lygodactylus methueni are found in the forests, and the Woodbush legless skink Acontophiops lineatus occurs in the montane grasslands. Another species, Eastwood's long-tailed seps Tetradactylus eastwoodae, was endemic to this IBA but is thought to be extinct, as pine trees were planted throughout its remaining habitat.
Berg adder Bitis atropos, montane dwarf burrowing skink Scelotes mirus, giant legless skink Acontias plumbeus, Cregoi's blind legless skink Typhlosaurus cregoi, Sekukhune flat lizard Platysaurus orientalis and northern crag lizard Pseudocordylus transvaalensis are all southern African endemics that may occur in the Wolkberg Mountains. Threatened mammals include pangolin Manis temminckii and leopard Panthera pardus.
The region is used extensively for forestry and plantations cover large sections of the IBA. The remaining indigenous forest is under considerable threat from the spread of alien trees from surrounding plantations and the activities within these plantations. It is unclear whether infrastructure such as power lines and roads have a negative impact on the IBA's trigger species; the same is true of tourism activities (especially 4x4 vehicles).
The IBA includes a number of State and private forest reserves as well as several formally protected nature reserves. About 24% of the IBA is formally protected. The reserves have management plans but a lack of funding and staff prevents them from being fully implemented. Friends of Haenertsburg is active in the IBA and is involved especially in efforts to conserve the grasslands around the town. A number of BirdLife South Africa-accredited bird guides operate in the IBA.