This reserve is situated 21 km west of Port Shepstone. It holds a spectacular gorge with many steep, sheer cliffs. Between the Oribi and Murchison Flats (plains that are north and south of the reserve respectively), the Umzimkulwana river has cut a 500-m-deep gorge through the soft sandstone down to the granite. The Umzimkulwana river is mature, with a bouldery substrate and short, shallow rapids with a few low waterfalls. Three artificial impoundments span the river within the reserve. Eight different vegetation-types have been distinguished in the reserve, the most extensive being forest and thicket. Shrubland, woodland, grassland and rocky communities occur to a lesser degree. Species-richness is high and the forests are dominated by trees such as Celtis, Chrysophyllum, Commiphora, Heywoodia, Margaritaria, Nuxia and Protorhus. Rocky outcrops are characterized by Tarchonanthus, Tricalysia, Cryptocarya and Loxostylis. The grassland is Ngongoni veld, and has a diversity of small flowering plants. In places there are stands of Protea.
See Box and Tables 2 and 3 for key species. The grassland and lightly wooded areas hold Balearica regulorum and Bucorvus cafer. The forest holds small numbers of Zoothera guttata (wintering), Tauraco corythaix, Campethera notata (at its northern and eastern extremity), Cossypha dichroa, Cercotrichas signata and Serinus scotops. The cliff just outside the boundary of the reserve holds a small breeding colony of Gyps coprotheres. These vultures visit the feeding station (restaurant) within the reserve whenever it is provisioned. The backwaters of the river hold Podica senegalensis.
Non-bird biodiversity: Botanically, the site is exceptionally rich in rare and localized species. Examples are Encephalartos ghellinckii, Leucospermum innovans, Podalyria burchellii, Acalypha wilmsii, Brachystelma tenellum, Huernia hystrix, Ceropegia rudatisii, Riocreuxia alexandrina and Plectranthus oribiensis.
Pressure/threats to key biodiversity
Prior to its proclamation as a Nature Reserve in 1950, most of the area was called Umzimkulwana State Forest (a demarcated government forest). The KwaZulu-Natal Nature Conservation Service currently administers the reserve. The nature of the terrain has precluded habitat modification, and the site exists in an almost pristine state. Private farms where sugar-cane is the main crop bound the reserve. A private commercial game-ranch borders the reserve on the eastern boundary, and occasionally game species that have been introduced here are seen within the reserve.