Terrestrial ecosystems and species face pressures from a range of human activities, including loss of natural habitat through intensive land uses (croplands, settlements, infrastructure, mining, plantations, and dams), invasive alien species, overuse of rangelands, pollution and waste, unsustainable biological resource use and climate change. These pressures interact in complex ways to impact biodiversity and disrupt important ecological processes.
Habitat loss
The loss of natural habitat is the single biggest cause of loss of biodiversity and ecosystem functioning in the terrestrial environment. Outright loss of natural habitat takes place mainly as a result of conversion of natural vegetation for cultivation of croplands, mining, plantation forestry, human settlements and other infrastructure development1. Patterns and trends linked to land-use and land cover change are closely linked to changes in terrestrial biodiversity and ecosystem extent. Habitat loss is also usually associated with habitat fragmentation, which further impacts ecological functioning and viability of species, particularly in the context of climate change and biological invasions.
Based on the national land cover, 81% of South Africa (986 051 km2) was in a natural state in 1990 (Table 1). By 2022 natural areas were estimated to have declined to 78% (946 090 km2). Habitat loss, as a result of historical (1750–1990) and recent (1990– 2022) clearing of natural habitat for field crops, horticultural crops and planted pastures, is the largest pressure on terrestrial ecosystems and biodiversity in South Africa and has affected 17% of the land area.
Clearing of natural habitat for new croplands between 1990 and 2022 amounted to 13 676 km2. The relatively mesic eastern portions of South Africa and the Fynbos and Renosterveld of the Cape lowlands were the most impacted by this clearing (Figure 1). Built-up areas (including rural and urban settlements, industrial and commercial areas and large infrastructure) also contribute to natural habitat loss and currently cover over 2.9% of the country. The rate of habitat loss linked to new built-up areas is increasing, especially in Gauteng and along the KwaZulu-Natal coast and adjacent interior. Plantation forestry (including non-native pine, eucalyptus and acacia species) is an important historical driver of habitat loss in mesic grassland regions, in particular (covering 21 573 km2). However, the rate of habitat loss to plantations is decreasing.
| Natural | Secondary natural | Artificial water | Built up | Crop | Mine | Plantation | Total 1990 | |
|---|---|---|---|---|---|---|---|---|
| Natural | 946 063 | 11 355 | 927 | 7 959 | 13 676 | 859 | 5 212 | 986 051 |
| Secondary natural | 10 | 30 164 | 82 | 1 065 | 3 854 | 100 | 799 | 36 074 |
| Artificial water | 6 | 2 035 | 3 417 | 37 | 75 | 17 | 39 | 5 626 |
| Built up | 1 | 2 118 | 7 | 24 597 | 452 | 53 | 92 | 27 320 |
| Crop | 8 | 18 984 | 119 | 1 072 | 120 557 | 340 | 465 | 141 545 |
| Mine | 2 | 1 528 | 84 | 36 | 19 | 1 123 | 33 | 2 825 |
| Plantation | 0 | 3 331 | 17 | 445 | 367 | 41 | 14 933 | 19 134 |
| Total 2022 | 946 090 | 69 515 | 4 653 | 35 211 | 139 000 | 2 533 | 21 573 | 1 218 575 |
Rangeland degradation
In addition to land clearing related habitat loss, large portions of South Africa’s rangelands have seen extensive modifications from centuries of livestock and more recently, wildlife farming. The ecological condition in these areas ranges from near-natural to critically modified depending on the degree to which ecosystem structure, function and composition have been altered through rangeland livestock and game management. Fire plays a crucial role in Fynbos, Grassland and Savanna ecology; disruption of natural fire regimes (fire season, frequency and intensity) presents an important pressure on biodiversity. Biological invasions also impact rangelands and are discussed below. Unfortunately, there is currently limited spatial data with which to assess these impacts at the scale of ecosystem types, though various assessments of South African rangelands have shown that bush encroachment is widespread. Recent work indicates lower levels of use and an improvement in primary productivity and natural vegetation cover in some rangelands2–4.
Biological invasions
Biological invasions, especially by invasive alien plants, are a major pressure on the biodiversity and ecosystem functioning of the terrestrial realm. A national report is released every three years – providing a comprehensive assessment of “The status of biological invasions and their management in South Africa”. The report details alien species introduction pathways, their distribution and abundance, their impacts and the various interventions that have been put in place5.
Of the 1 715 terrestrial alien species recorded (or assumed to be present) in South Africa, 611 are known to be invasive, 117 are known to be naturalised but not invasive, and 482 are present, but not naturalised6. For the remainder (505 species), there is insufficient information to assign them to an introduction status category. While the majority of invasive species have relatively restricted distributions there are some (plants and birds in particular) that are widespread. Invasive species have a range of impacts on biodiversity, displacing indigenous species, disturbing habitats and disrupting ecosystem functioning7. Australian acacias, for example, can form closed canopy stands that exclude indigenous species, change fire regimes and impact surface water runoff, negatively impacting biodiversity and water catchment function. Herbaceous and succulent species such as Triffid Weed (Chromolaena odorata) can severely reduce rangeland productivity and thus the livelihoods of rural people; while invasive grasses such Reed Meadow (Glyceria maxima) and Giant Reed (Arundo donax) can dominate riparian areas and displace native species. Examples of severe impacts in other high-level taxa include competitive displacement and predation on native species by domestic cats (Felis catus) and from invasive birds such as Rose-ringed parakeet (Psittacula krameria), House crow (Corvus splendens), and Common Myna (Acridotheres tristis) 10.1038/s41597-025-05184-5. Overall, alien plants are the most diverse, widespread and damaging group of invaders in South Africa. Furthermore, it is clear that South Africa has a major alien plant invasion debt. Over half of the taxa that are present are plants, and the range of almost all invasive alien plants have increased significantly8. This is a major cause for concern, as it clearly indicates that problems associated with alien species are set to increase.
Climate change
Since the 2018 NBA, there has been a global acceleration in the rates of global warming, with 2024 exceeding the historic baseline by 1.5 °C for the first time read more. The interior of southern Africa continues to warm faster than the global terrestrial mean9. The impacts of Anthropogenic climate change have become increasingly visible in most ecological processes with disruptions evident from the genetic to the landscape levels. Abiotic pressures affecting the terrestrial realm include increases in dry spell duration, mean and maximum temperatures, wind, wildfires, sea level; and increases in the frequency and intensity of storm surges, extreme rainfall events and both more frequent and hotter hot days10. Annual rainfall has both increased and decreased in different regions and overall changes in rainfall seasonality have been noted. Evidence of early impacts of climate change on species is rapidly accumulating, with 70 amphibian species contracting their geographic ranges, at least partly due to climate change impacts on freshwater systems. Large-scale die-offs of desert plant communities have been documented, along with shifting migration times and range contractions for bird species. Fynbos community composition has also been shown to have altered due to climate change. Over the past century one of the most pervasive structural changes observed has been an increase in the density and spread of woody species in grassy biomes. This global trend, known as bush encroachment or woody thickening, is widespread in southern African grasslands, open savannas and mixed grass/shrub ecosystems. Research has shown that a changing climate and rising CO2 are probable background drivers of extensive and broad-scale switches towards greater woody plant cover, but that other important drivers (fire and grazing/browsing) influence the rate of this change11–13. These widespread ecological shifts have triggered plant and animal community reorganisations, net declines in biodiversity and changes in landuse activities. These alarming shifts, which are projected to intensify rapidly as climate thresholds are exceeded, drive the urgent need for climate change mitigation and management of interacting change drivers14. Climate impacts on biodiversity will be amplified by land transformation and biological invasions as discussed above. Since progressive climatic, CO2 and resulting biodiversity changes are now inevitable, a fundamental review of conservation objectives and desired outcomes that accommodate climate change impacts is essential, along with planning and implementation of targeted conservation interventions. These need to be supported by a wider array of long-term monitoring efforts, including the effectiveness of the new climate-smart conservation approaches.
Biological resource use
Biological resource use directly targets specific wildlife species and includes the hunting and trapping of animals as well as the harvesting of plants. In South Africa, animals and plants are commonly used as traditional medicine for both the treating of ailments and for cultural purposes. The NBA 2018 reported that over 2 000 indigenous plant species have documented traditional medicinal uses. Some 656 medicinal plant species are common in trade and many are unsustainably harvested, with 184 species declining due to excessive use and 56 listed as threatened. Approximately 147 vertebrate species, representing about 9% of the total number of vertebrate species in South Africa, are traded for traditional purposes. Vultures are particularly threatened by cultural use and it has been estimated that 29% of local vulture deaths are due to harvesting for traditional purposes. Harvesting for traditional medicine has increased pressure on endemic species of reptiles, such as the Sungazer Lizard (Smaug giganteus). Expansion of human settlements, especially in areas bordering protected areas, has resulted in increased hunting intensity for bushmeat and/or traditional medicine and cultural regalia, with species including Leopard (Panthera pardus), Temminck’s Ground Pangolin (Smutsia temminckii) and Oribi (Ourebia ourebi).
Other Pressures
Waste generated by mining, agriculture, energy production, manufacturing and urban settlements causes water pollution, soil pollution and air pollution, which impact on ecosystems, species and ecological processes – often substantial distances away from the original pollution source. Proactive mapping and management of noise sensitive areas is recommended while scientists continue to strengthen the knowledge for soundscapes and the impacts of noise pollution. Renewables energy installations are a new form of land use expanding throughout South Africa. Crucial for the just energy transition and supporting the reduction in reliance on fossil fuels, these developments present novel pressures on biodiversity and ecosystems and innovative mitigation initiatives are being implemented with the industry.
Recommended Citation
Skowno, A.L., Mogajane, K., Von Maltitz, G.P., Zengeya, T., & Raimondo, D.C. 2025. Pressures on biodiversity: Terrestrial realm. National Biodiversity Assessment 2025. South African National Biodiversity Institute. http://nba.sanbi.org.za/.