Page 56 - State of Biodiversity 2023-2024

4.5. THREATS TO BIODIVERSITY IN ETHEKWINI MUNICIPALITY
Some of the major threats to biodiversity include:
• Transformation of natural areas (habitat destruction, degradation, and fragmentation)
• Introduction and the spread of invasive alien species
• Over-exploitation (e.g., harvesting, and illegal and
mining)
• Pollution and diseases
• Human-induced climate change
• Changes to the quantity and quality of water within
aquatic systems (e.g., impoundments and point source discharges)
Due to the lack of quantitative data relating to many of these threats, this report will only focus on transformation, invasive alien species and climate change. More information will be included as it becomes available such as on land tenure in rural areas, however, in this year’s report, an insert on the threats that are posed by sand mining has been included.
Durban’s rich natural resource base has been under significant pressure and negatively impacted over the past 150 years, initially by extensive agriculture, and then increasingly by rapid urbanization, resulting in the cover of the original vegetation types being reduced to approximately one-third of the original extent. Rates of loss of natural habitat are particularly high in KwaZulu-Natal, averaging 1.2% per annum between 1994 and 2011, and likely to be substantially higher in the more densely populated Durban (Jewitt et al., 2015).
Historical aerial photography provides evidence that grassy environments, maintained by fire, dominated the landscape, with forest and savanna systems restricted to areas where fire was excluded. In addition to complete transformation, many remnant grassland patches have been degraded through altered fire and grazing regimes, plant harvesting for traditional and horticultural uses, and nutrient enrichment.
There is also a general ongoing successional trend for grassland to be replaced by woody vegetation. Eastern Scarp Forest represents a notable outlier from the rest of the vegetation types in the EMA which have suffered area losses, in that the extent of this vegetation type has expanded relative to reference conditions. This expansion is attributed to the reduced influence of fire, habitat fragmentation, and increased atmospheric CO2, which favours woody plants (often alien plants), with their C3 photosynthetic pathway.
All these types of shifts from natural vegetation into transformed land result in irreversible change with loss of habitat, species, genetic variability, and connectivity all being removed. This ultimately impacts on and reduces the effectiveness and range of environmental goods and services, which these areas could provide to both humans and other natural systems. Many of these services, such as the supply of water and food, have a direct impact on people’s lives and as these habitats are degraded, these services diminish.
54 STATE OF BIODIVERSITY REPORT 2023/2024