The site is located c. 15 km north of Howick. Geologically, most of it consists of Beaufort shales and sandstones, traversed by dolerite sills and dykes. Mount Gilboa, the highest point and a dominant feature of the IBA, is 1 768 m a.s.l. The Karkloof valley lies between 1 100 and 1 250 m a.s.l.
Mistbelt forests are found on south-facing slopes. The most extensive patch is known as Karkloof Forest and a large portion of it falls within Karkloof Nature Reserve. Grasslands once occurred throughout the area but are now largely restricted to the high-lying slopes and plateaus in the northern parts of the IBA. The Karkloof valley has been heavily transformed by agricultural activities. The area forms part of the headwaters of three river systems: the Mooi, Umgeni and Umvoti. Wetlands, vleis and flooded grassland are found throughout the IBA, the most important complex of which is found in the Karkloof and Mount Gilboa nature reserves. The main vegetation types are Southern Mistbelt Forest, Drakensberg Foothill Moist Grassland and Midlands Mistbelt Grassland.
The climate is temperate, with mist frequent in summer and frost in winter. Rainfall averages 1 200 mm p.a., falling mostly in summer.
The vleis and wetlands support one of the most important breeding populations of Wattled Crane Bugeranus carunculatus in KwaZulu-Natal, with an estimated 10% of the population found in the area. Grey Crowned Crane Balearica regulorum also nests in the wetlands, whereas Blue Crane Anthropoides paradiseus breeds in the surrounding grasslands. Large flocks of all three crane species are regularly found foraging in agriculture lands during the non-breeding season.
African Grass Owl Tyto capensis and African Marsh Harrier Circus ranivorus are permanent residents in the wetlands, while the surrounding grasslands hold Cape Grassbird Sphenoeacus afer, Red-winged Francolin Scleroptila levaillantii, Striped Flufftail Sarothrura affinis, Denham's Bustard Neotis denhami, Black-winged Lapwing Vanellus melanopterus and Southern Ground-Hornbill Bucorvus leadbeateri.
There are many important species in the forests, including small numbers of the threatened Cape Parrot Poicephalus robustus, and Eastern Bronze-naped Pigeon Columba delegorguei has been recorded. An isolated endemic subspecies of Crested Guineafowl, Guttera pucherani symonsi, is found only here and in a couple of small forests nearby. Common species of the forest floor and forest edge are Red-necked Spurfowl Pternistis afer and Lemon Dove Aplopelia larvata. Bird parties are frequent and typical forest birds include Trumpeter Hornbill Bycanistes bucinator, Crowned Hornbill Tockus alboterminatus, Narina Trogon Apaloderma narina, Orange Ground Thrush Zoothera gurneyi, Bush Blackcap Lioptilus nigricapillus, Knysna Turaco Tauraco corythaix, Olive Woodpecker Dendropicos griseocephalus, Grey Cuckooshrike Coracina caesia, Chorister Robin-Chat Cossypha dichroa, White-starred Robin Pogonocichla stellata, Yellow-throated Woodland Warbler Phylloscopus ruficapilla, Blue-mantled Crested-Flycatcher Trochocercus cyanomelas, Olive Bush-Shrike Chlorophoneus olivaceus, Swee Waxbill Coccopygia melanotis and Forest Canary Crithagra scotops. Forest predators include Forest Buzzard Buteo trizonatus, Crowned Eagle Stephanoaetus coronatus and Black Sparrowhawk Accipiter melanoleucus, and at night African Wood Owl Strix woodfordii. The quiet forest river streams hold habitat for Mountain Wagtail Motacilla clara.
Gurney's Sugarbird Promerops gurneyi occurs where protea woodland, especially Protea roupelliae, dominates the grassland. Martial Eagle Polemaetus bellicosus and Rufous-breasted Sparrowhawk Accipiter rufiventris breed on the forest margin and forage in the grasslands. Sentinel Rock Thrush Monticola explorator and Buff-streaked Chat Campicoloides bifasciata inhabit rocky outcrops. Cape Vulture Gyps coprotheres is a regular visitor.
Globally threatened species are Wattled Crane (nine breeding pairs and flocks of 10–25 individuals), Blue Crane (six breeding pairs and flocks of up to ten individuals), Grey Crowned Crane (eight breeding pairs and flocks of 60–80 individuals), Crowned Eagle and Bush Blackcap. Regionally threatened species are Striped Flufftail, Cape Parrot, African Grass Owl and Orange Ground Thrush. Restricted-range and biome-restricted species are Forest Buzzard, Knysna Turaco, Grey Cuckooshrike, Bush Blackcap, Orange Ground Thrush (up to 20 individuals and a possible ten breeding pairs have been recorded in a single forest patch), Buff-streaked Chat, Chorister Robin-Chat, Yellow-throated Woodland Warbler, Olive Bush-Shrike, Swee Waxbill and Forest Canary.
Important mammals include samango monkey Cercopithecus mitis, blue duiker Philantomba monticola, oribi Ourebia ourebi, tree hyrax Dendrohyrax arboreus, serval Felis serval and aardvark Orycteropus afer. The South African endemic grey rhebok Pelea capreolus also occurs. An exceptionally rare and localised butterfly, Karkloof blue Orachrysops ariadne, occurs in high-lying grasslands. Several rare trees grow in the forest, including Ocotea bullata, Curtisia dentata and Scolopia flanaganii, with Alberta magna on the margin. Near-endemic plants in the grassland include Geranium natalense and Dierama luteo-albidum. The threatened and highly localised Hilton daisy Gerbera aurantiaca also occurs.
The genetic integrity of the unique, isolated population of Crested Guineafowl is threatened by ill-informed attempts by neighbouring landowners to introduce the species to forest patches where it does not occur. A different subspecies is common in Zululand, and these are the birds that might well be introduced.
The forest holding represents less than a third of the whole of Karkloof Forest, and even this is a pale shadow of the original forest: in 1860 it was at least 34 000 ha in extent and housed African elephant Loxodonta africana, African buffalo Syncerus caffer and black rhinoceros Diceros bicornis. The forest has been plundered of its best timber since 1845. The rarity of the Cape Parrot here must be related to the reduction of Podocarpus falcatus, its favourite food plant.
The invasion of alien weeds is a serious challenge, but is being tackled. The vleis are vulnerable to poorly timed fires that kill Wattled Crane chicks; this problem has largely been addressed.
Blue Swallow Hirundo atrocaerulea occurred in Karkloof until the 1950s and up to four pairs nested in the Blinkwater Nature Reserve before 1980, dwindling to one pair in 1988, and to extinction in 1990. The reason for its disappearance is not fully understood.
Two provincial nature reserves are encompassed within the IBA: Karkloof Nature Reserve and Blinkwater Nature Reserve. Both fall under the management of EKZNW. Sections of Karkloof Nature Reserve are owned by the State, Sappi, WCT and private landowners. The rest of the area is owned by multiple landowners, the majority of whom are private. Most of the area forms part of the Karkloof Conservancy, which is very active and has a strong conservation ethic. This is reflected by the number of Biodiversity Stewardship sites in various stages of proclamation, including Little Springs, Gartmore (Biodiversity Agreement), Mbona Private Nature Reserve (Nature Reserve), Mount Gilboa Nature Reserve (Nature Reserve) and Dartmore (proclaimed as part of the Karkloof Nature Reserve).
No permanent EKZNW staff are present in either Karkloof or Blinkwater nature reserves and this makes managing and dealing with issues such as poaching difficult. However, WCT actively patrols and manages the grassland sections of Dartmore and is also active in Karkloof Nature Reserve. All three crane species are actively monitored and counted during an annual aerial census by EKZNW and EWT.
Adie H. 2013. Southern KwaZulu-Natal mistbelt forest assessment. Unpublished report. Ezemvelo KZN Wildlife.
Adie H, Rushworth I, Lawes M. 2013. Pervasive, long-lasting impact of historical logging on composition, diversity and above ground carbon stocks in Afrotemperate forest. Forest Ecology and Management 310: 887–895.
Downs CT, Pfeiffer M, Hart L. In press. Fifteen years of annual Cape Parrots (Poicephalus robustus) census: current population trends and conservation contributions. Ostrich.
Savy C. 2003. Conserving Wattled Crane (Grus carunculatus) on private land in KwaZulu-Natal, South Africa: attitudes, economics and potential incentives. MSc thesis, University of Cape Town, South Africa.
Taylor HC. 1961. The Karkloof forest: a plea for its protection. Forestry in South Africa 1: 123–130.
Taylor PB. 1997b. South African palustrine wetlands: the results of a survey in summer 1995/96. ADU Research Report No. 24. Cape Town: Avian Demography Unit, University of Cape Town.