Estuary Health Index
In South Africa estuary health is measured as the difference between natural (or reference) and present-day conditions. Using a standardised Estuarine Health Index (EHI)[i]. The index collates information on physical and chemical drivers (e.g. freshwater inflows, estuary mouth changes and water quality), biological characteristics ( e.g. primary production from phytoplankton to complex plants) and living organisms (plants, invertebrates, fish and birds) to classify the estuary on a scale from A – Natural to F – Extremely Degraded.
The Estuary Health Index
The index is widely used by various authorities to:
- Describe the state of the resource, g. the National Biodiversity Assessment conducted every five years to support management in terms of the National Environmental Management: Biodiversity Act No. 10 of 2004
- Determine minimum environmental freshwater (quantity and quality) requirements for each estuary as mandated by the National Water Act No. 36 of 1998
- Identify conservation opportunities and priorities in conservation planning, including Spatial Development Frameworks and Environmental Management Frameworks at local government level and Protected Areas Expansion Strategies at national and provincial levels
- Inform land-use planning in terms of Environmental Impact Assessment (in terms of the National Biodiversity Management Act No. 107 of 1998), Water Use Licence Applications (in terms of National Water Act No. 36 of 1998), and applications for Mining Licences and Mining Rights (in terms of the Minerals and Petroleum Development Act No. 28 of 2002)
State of KZN Estuaries
There are no estuaries in KwaZulu-Natal that are in a natural, unmodified state, despite several estuaries having formal protection and being situated within proclaimed protected areas[i]. All of KZN’s estuaries have been subject to human uses that have impacted estuary health. Twelve (16%) of the province’s estuaries are in a near-natural state, but the majority range from Moderately Modified to Extremely Degraded.
Present Ecological Status of KwaZulu-Natal estuaries
Pressures and Threats
Anthropogenic pressures and threats to estuary health are wide-ranging, including direct and indirect modification and use, and chronic pressures such as climate change. The main impacts present in KZN’s estuaries are:
- Chronic pollution (domestic and industrial wastewater, stormwater, solid waste) – medium to high in 88% of estuaries
- Changes to river flows (dams, stream flow reduction, wastewater) – medium to very high changes in flow in 72% of estuaries
- Fisheries (fish and bait) – medium to very high in 58% of estuaries
- Estuary mouth manipulation (artificial breaching) – occurs in 53% of estuaries
- Habitat loss (change of land use and poor water quality) – high to very high in 63% of KZN estuaries
- Alien species (plants, fish and invertebrates) – occur in 61% of estuaries
Summary of KwaZulu-Natal estuaries pressures and threats
To meet national environmental health and conservation targets2,[i] 18 new estuary-related formal protected areas will need to be proclaimed and 18 of KZN’s estuaries require active management interventions and rehabilitation to achieve their Recommended Ecological Category. These measures can be designed and implemented through an Estuary Management Plan (EMP) in terms of the National Environmental Management: Integrated Coastal Management Act No. 24 of 2008. These EMPs must be developed in collaboration with all stakeholders with some dependence on the individual estuary, to support planning and sustainable resource use through the management of human activities in and around the system. Seven (9%) of KwaZulu-Natal estuaries have EMPs, including one that deals exclusively with artificial breaching. As at 1st November 2019 eight plans were in progress and six additional plans have been proposed; the remaining 55 estuaries have no formal planning initiatives.
Conservation Status of KZN’s Estuaries (left) and State of Estuary Management Plans in KZN (right)
1. Turpie, J.K., Taljaard, S., Van Niekerk, L., Adams, J., Wooldridge, T., Cyrus, D., Clark, B., Forbes, N., 2012. The Estuary Health Index: A standardised metric for use in estuary management and the determination of ecological water requirements. WRC Report No. 1930/01/12. Cape Town.
2. Van Niekerk, L., Adams, J.B., Lamberth, S.J., MacKay, C.F., Taljaard, S., Turpie, J.K., Weerts, S. & Raimondo, D.C., 2019 (eds). South African National Biodiversity Assessment 2018: Technical Report. Volume 3: Estuarine Realm. CSIR report number CSIR/SPLA/EM/EXP/2019/0062/A. South African National Biodiversity Institute, Pretoria. Report Number: SANBI/NAT/NBA2018/2019/Vol3/A.
3. Van Niekerk, L,., Turpie, J., (eds), 2012. South African National Biodiversity Assessment 2011: Technical Report. Volume 3: Estuary Component. CSIR Report No. CSIR/NRE/ECOS/ER/2011/0045/B. Stellenbosch.
ORI • EDTEA
Fiona MacKay • Bianca McKelvey • Bronwyn Goble • Tshegofatso Ramohlale