Thickets have perplexed botanists for decades. Also called karoo, savanna, and forest, thickets share many characteristics with these vegetation types, but do not fit snuggly into any of them. As such, thickets have recently been recognised as a distinct South African biome. Written by: Adriaan Grobler and Catherine Browne
In its typical form, a thicket forms a dense, almost impenetrable tangle of trees, shrubs, and vines, many armed with thorns and spines. Historically, thickets have received very little attention compared to their more inviting floral neighbours – the fynbos and succulent karoo.
Thicket forms one of the major vegetation types in all three of South Africa’s Biodiversity Hotspots: the Cape Floristic Region, the Maputaland-Pondoland-Albany, and the Succulent Karoo hotspots. Thicket can be found along the south-eastern coast of South Africa between the Gouritz River in the west and the Kei River in the east, and it is the dominant vegetation in the central and eastern Little Karoo, and in the major river valleys coastward of the Great Escarpment. The largest thicket areas occur in the valleys of the Gamtoos, Sundays and Fish rivers.
Thickets are rich in plant life, and the plants come in a myriad of forms, including trees and tall shrubs, low and dwarf shrubs, succulents, vines, bulbs, and grasses, as well as perennial and annual herbs. This great diversity of plant types is unmatched by any other of South Africa’s biomes. After the succulent karoo, thickets have the second-largest succulent flora in the world, and half of the 344 succulent plants found here are endemic.
Thicket also has the richest mammal fauna of any area with a similar climate. At 106 species, it is home to almost half of South Africa’s mammal fauna, including the Big Five: African elephant, black rhino, Cape buffalo, Cape leopard and lion. Similarly, thickets support close to half of South Africa’s bird fauna. 349 bird species find refuge here, making it one of the richest bird environments among similar-sized regions outside of the tropics. Trumpeter hornbills, narina trogons, orange-breasted sunbirds and Knysna turacos are bird species that one will encounter in a thicket. The rare and threatened Cape parrot can also be found in the thicket of the Amathole Mountains.
Close to 10% of thicket has been obliterated, primarily by crop production, unsustainable livestock farming and urbanisation. A further 55% of thicket is heavily degraded, and only about 10% remains pristine. Most of the unspoiled thicket can be found within the borders of state-owned nature reserves and national parks. Foremost among these is the Addo Elephant National Park, which currently covers 180,000 ha. The area consists predominantly of thicket but also includes subtropical and temperate forests, fynbos, grassland, karoo, and savanna. In addition to hosting elephant, black rhino, buffalo, zebra, leopard, lion, spotted hyena and numerous antelope species, the thicket at Addo is also home to the largest remaining population of the threatened Addo flightless dung beetle.
In light of the unique biodiversity of thicket and the fact that it is not yet adequately protected, the Subtropical Thicket Ecosystem Planning project (STEP) identified a vast network of corridors that, if protected, will ensure the persistence of the irreplaceable natural heritage that we find here. This network covers about 22% of thicket’s core area. It will need to be protected in its entirety to allow the continued functioning of thicket, especially in the face of climate change.
The Botanical Society of South Africa is committed to conserving our unique floral heritage. You, too can help make a difference for the conservation of South Africa’s vegetation, to ensure your children and their children get to explore and enjoy the wonders of biodiversity we have today.
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