ZA091
Outeniqua mountains


Year of compilation: 2001

Site description
The Outeniquas rise from the coastal plain north of Mossel Bay and run c.100 km to the east before dropping into the Keurbooms river valley, which enters the ocean at Plettenberg Bay. They run parallel to the Swartberg (IBA ZA085). The southern slopes are gentle, and rise to form a series of peaks; the steep northern slopes drop sharply into the Little Karoo, which forms a broad low-lying valley north of the Outeniquas. The stark variation in altitude and conditions yields a wide diversity of habitats, resulting in a distinct contrast between the moist high-altitude montane fynbos, the karroid and renosterveld shrubland on the northern slopes, where low rainfall promotes non-fynbos scrub, and Afromontane forest on the mesic south-facing slopes.

Key biodiversity
See Box and Tables 2 and 3 for key species. The IBA is extremely rich in birds of fynbos, forest and the arid zone. At high altitudes, the fynbos holds Nectarinia violacea and Serinus totta. Promerops cafer and Serinus leucopterus breed and forage in the larger Protea stands. Low, dense resteoid thicket holds Sarothrura affinis and may hold Turnix hottentotta nana. Bradypterus victorini is locally common in the seeps and neighbouring mesic fynbos, and Chaetops frenatus and Geocolaptes olivaceus occur on exposed rocky slopes, primarily above 1,000 m. The lowland karroid plains north of the range are particularly good for Eupodotis vigorsii, Cercomela schlegelii and Malcorus pectoralis. Circus maurus and Falco naumanni are occasionally seen quartering the plains. Serinus alario occurs whenever seeding grass and water abound. The isolated forest patches on the southern slopes of the Outeniquas hold several forest endemics including Tauraco corythaix, Campethera notata, Telophorus olivaceus, Cossypha dichroa, Bradypterus sylvaticus and Serinus scotops. Other forest species include Apaloderma narina and Stephanoaetus coronatus.

Non-bird biodiversity: This area is thought to hold over 2,000 plant species, many of which are endemic and threatened. Barbus tenuis (EN) is restricted to the tributaries of the Keurbooms and Gourits rivers; the former forms the northern boundary of this IBA and may hold small populations of this threatened and highly localized fish species.



Pressure/threats to key biodiversity
The major part of this mountain range is protected as the Outeniqua Mountain Catchment Area (158,515 ha, of which 72,300 ha is demarcated State Forest, 461 ha undemarcated State Forest and 85,754 ha proposed Mountain Catchment Area), established in 1970. The Mountain Catchment Areas were proclaimed in accordance with the policy of the former Directorate of Forestry and Environmental Conservation to extend reserves for more effective water management and are now under the control of the Department of Water Affairs and Forestry (DWAF).

Invasive non-native trees of Acacia, Hakea and Pinus pose a serious threat to both vegetation and water conservation in these mountains. Locally, these exotic taxa can dominate thousands of hectares, significantly modifying soil composition, fire regime and natural plant and animal communities, threatening many indigenous species with extinction. Alien trees are also known to accelerate riverbank erosion and reduce in-stream flow through excessive transpiration. The control of invasive alien taxa is the largest task facing most managers in this biome. Biocontrol agents, including fungus and insects, have been introduced to prevent the spread of alien species; some of these agents have been extremely successful. The ‘Working for Water’ programme, initiated by DWAF, involves physical removal of alien plants in water catchment areas. This ingenious programme increases water run-off and simultaneously employs people.This IBA is located close to Knysna, the hub of the world-famous Garden Route, and many thousands of tourists pass through the area each year. The mountain chain is used extensively for hiking and other recreational purposes. Greater human usage of this mountain range increases the chance dispersal of the non-native Argentine ant Iridomyrmex humilis into these ecosystems. This ant ousts indigenous ant species that are responsible for seed dispersal in numerous myrmecochorous fynbos plants, and this could have a major negative impact on the local biota.

Threats on the karroid plains of the Little Karoo to the north include overgrazing of the surrounding farmland, resulting in the degradation of habitat, potentially reducing populations of wide-ranging, sensitive species. Several pesticides and poisons are used in the farming areas. The effects that they are having on bustards, cranes, raptors and other tertiary consumers in the region are currently unknown.


Recommended citation
BirdLife International (2022) Important Bird Areas factsheet: Outeniqua mountains. Downloaded from http://www.birdlife.org on 07/08/2022.