Ecosystem threat status

Lara van Niekerk; Andrew L. Skowno; Kerry Sink; Linda R. Harris

The Estuarine realm is one of the most threatened in South Africa, in terms of both number of ecosystem types and by area. Of South Africa’s 22 estuarine ecosystem types, 91% are threatened with 5% Critically Endangered, 41% Endangered and 45% Vulnerable. Of total estuarine area, 99% is threatened with 1% Critically Endangered, 72% Endangered and 26% Vulnerable. Unsustainable land and sea use can undermine the benefits from healthy ecosystems and the natural capital that can support a thriving economy (key message A2).

Knysna is one of two estuarine bays inside South Africa and is an example of a Vulnerable system. (© Matt Dubber)

91%
of 22 ecosystem types
Threatened

41%
of 22 ecosystem types
Endangered

5%
of 22 ecosystem types
Critically Endangered

45%
of 22 ecosystem types
Vulnerable

Ecosystem threat status assessment

The estuarine realm is one of the most threatened in South Africa, in terms of both the number of ecosystem types and by area¹.

About 91% of the 22 estuary types are threatened, with 5% Critically Endangered, 41% Endangered and 45% Vulnerable. Of the total estuarine area, 99% is threatened, with 1% Critically Endangered, 72% Endangered and 26% Vulnerable.

Multiple interventions are required to avoid further decline in health. These include protection of freshwater inflow to estuaries and the sea, restoration of water quality, reduction in fishing effort and avoidance of mining, infrastructure development, and crops in the estuarine functional zone.

Figure 1. Map showing the distribution of threatened estuarine ecosystems according to the IUCN Red List of Ecosystems (size of the dot represents area of the individual estuary). The inset graph shows the number and proportion of ecosystem types that fall within each threat status category.

Figure 2. Ecosystem threat status of South Africa’s estuaries presented as percentage of ecosystem types (A) and percentage ecosystem extent (B).

Table 1. Ecosystem threat status of South Africa’s estuaries tabulated by number of estuaries in a type, estuary types, extent and percentage area in a biogeographical region.

		Critically Endangered	Endangered	Vulnerable	Least Concern
Cool Temperate	No. estuaries	0	24	9	0
	No. estuary types	0	6	2	0
	Extent (ha)	0	361	5	0
	Percentage (%)	0	99	1	0
Warm Temperate	No. estuaries	0	3	67	54
	No. estuary types	0	1	4	2
	Extent (ha)	0	143	282	17
	Percentage (%)	0	32	64	4
Subtropical	No. estuaries	1	9	121	0
	No. estuary types	1	2	3	0
	Extent (ha)	28	926	149	0
	Percentage (%)	3	84	14	0
Tropical	No. estuaries	0	0	2	0
	No. estuary types	0	0	1	0
	Extent (ha)	0	0	82	0
	Percentage (%)	0	0	100	0

Critically Endangered

Following the application of 2024 IUCN guidelines for red listing ecosystems and drawing from previous estuarine NBA assessments, the Subtropical Estuarine Bay ecosystem type, represented by Durban Bay, is the only system that triggered Critically Endangered.

Endangered

Nine estuarine ecosystem types were classified as Endangered, with 6 types in the Cool Temperate, 1 in the Warm Temperate and 2 in the Subtropical biogeographical region.

Cool Temperate Estuarine Lagoon
Cool Temperate Estuarine Lake
Cool Temperate Large Fluvially Dominated
Cool Temperate Predominantly Open
Cool Temperate Large Temporarily Closed
Cool Temperate Arid Predominantly Closed
Warm Temperate Estuarine Lake
Subtropical Large Fluvially Dominated
Subtropical Estuarine lake

Vulnerable

Overall 10 estuarine ecosystem types were classified as Vulnerable, with 2 types in the Cool Temperate, 4 in the Warm Temperate, 3 in the Subtropical, and 1 in the Tropical biogeographical region.

Cool Temperate Small Temporarily Closed
Cool Temperate Small Fluvially Dominated
Warm Temperate Estuarine Bay
Warm Temperate Large Fluvially Dominated
Warm Temperate Predominantly Open
Warm Temperate Large Temporarily Closed
Subtropical Predominantly Open
Subtropical Large Temporarily Closed
Subtropical Small Temporarily Closed
Tropical Estuarine Lake

Table 2. Ecosystem threat status of South Africa’s estuaries, ordered from west to east coast.

Estuary name	Estuary type	Threat status
Orange	Cool Temperate Large Fluvially Dominated	Endangered
Buffels	Cool Temperate Arid Predominantly Closed	Endangered
Swartlintjies	Cool Temperate Arid Predominantly Closed	Endangered
Spoeg	Cool Temperate Arid Predominantly Closed	Endangered
Groen	Cool Temperate Arid Predominantly Closed	Endangered
Sout (Noord)	Cool Temperate Arid Predominantly Closed	Endangered
Olifants	Cool Temperate Predominantly Open	Endangered
Jakkals	Cool Temperate Large Temporarily Closed	Endangered
Wadrift	Cool Temperate Arid Predominantly Closed	Endangered
Verlorenvlei	Cool Temperate Estuarine Lake	Endangered
Groot Berg	Cool Temperate Predominantly Open	Endangered
Langebaan	Cool Temperate Estuarine Lagoon	Endangered
Diep/Rietvlei	Cool Temperate Large Temporarily Closed	Endangered
Sout (Wes)	Cool Temperate Large Temporarily Closed	Endangered
Disa	Cool Temperate Large Temporarily Closed	Endangered
Wildevoëlvlei	Cool Temperate Large Temporarily Closed	Endangered
Schuster	Cool Temperate Small Temporarily Closed	Vulnerable
Krom	Cool Temperate Small Temporarily Closed	Vulnerable
Silwermyn	Cool Temperate Large Temporarily Closed	Endangered
Zand	Cool Temperate Large Temporarily Closed	Endangered
Zeekoei	Cool Temperate Estuarine Lake	Endangered
Eerste	Cool Temperate Large Temporarily Closed	Endangered
Lourens	Cool Temperate Small Temporarily Closed	Vulnerable
Sir Lowry’s Pass	Cool Temperate Small Temporarily Closed	Vulnerable
Steenbras	Cool Temperate Small Fluvially Dominated	Vulnerable
Rooiels	Cool Temperate Small Temporarily Closed	Vulnerable
Buffels (Oos)	Cool Temperate Small Temporarily Closed	Vulnerable
Palmiet	Cool Temperate Large Temporarily Closed	Endangered
Bot/Kleinmond	Cool Temperate Estuarine Lake	Endangered
Onrus	Cool Temperate Small Temporarily Closed	Vulnerable
Klein	Cool Temperate Estuarine Lake	Endangered
Uilkraals	Cool Temperate Predominantly Open	Endangered
Ratel	Cool Temperate Small Temporarily Closed	Vulnerable
Heuningnes	Warm Temperate Estuarine Lake	Endangered
Klipdrifsfontein	Warm Temperate Small Temporarily Closed	Least Concern
Breede	Warm Temperate Predominantly Open	Vulnerable
Duiwenhoks	Warm Temperate Predominantly Open	Vulnerable
Goukou	Warm Temperate Predominantly Open	Vulnerable
Gouritz	Warm Temperate Predominantly Open	Vulnerable
Blinde	Warm Temperate Small Temporarily Closed	Least Concern
Tweekuilen	Warm Temperate Small Temporarily Closed	Least Concern
Gericke	Warm Temperate Small Temporarily Closed	Least Concern
Hartenbos	Warm Temperate Large Temporarily Closed	Vulnerable
Klein Brak	Warm Temperate Large Temporarily Closed	Vulnerable
Groot Brak	Warm Temperate Large Temporarily Closed	Vulnerable
Maalgate	Warm Temperate Large Temporarily Closed	Vulnerable
Gwaing	Warm Temperate Small Temporarily Closed	Least Concern
Kaaimans	Warm Temperate Predominantly Open	Vulnerable
Touw/Wilderness	Warm Temperate Estuarine Lake	Endangered
Swartvlei	Warm Temperate Estuarine Lake	Endangered
Goukamma	Warm Temperate Large Temporarily Closed	Vulnerable
Knysna	Warm Temperate Estuarine Bay	Vulnerable
Noetsie	Warm Temperate Small Temporarily Closed	Least Concern
Piesang	Warm Temperate Large Temporarily Closed	Vulnerable
Keurbooms	Warm Temperate Predominantly Open	Vulnerable
Matjies	Warm Temperate Small Temporarily Closed	Least Concern
Sout (Oos)	Warm Temperate Predominantly Open	Vulnerable
Groot (Wes)	Warm Temperate Small Temporarily Closed	Least Concern
Bloukrans	Warm Temperate Small Fluvially Dominated	Least Concern
Lottering	Warm Temperate Small Fluvially Dominated	Least Concern
Elandsbos	Warm Temperate Small Fluvially Dominated	Least Concern
Storms	Warm Temperate Small Fluvially Dominated	Least Concern
Elands	Warm Temperate Small Fluvially Dominated	Least Concern
Groot (Oos)	Warm Temperate Small Fluvially Dominated	Least Concern
Tsitsikamma	Warm Temperate Small Temporarily Closed	Least Concern
Klipdrif (Oos)	Warm Temperate Small Temporarily Closed	Least Concern
Slang	Warm Temperate Small Temporarily Closed	Least Concern
Kromme	Warm Temperate Predominantly Open	Vulnerable
Seekoei	Warm Temperate Large Temporarily Closed	Vulnerable
Kabeljous	Warm Temperate Large Temporarily Closed	Vulnerable
Gamtoos	Warm Temperate Predominantly Open	Vulnerable
Van Stadens	Warm Temperate Large Temporarily Closed	Vulnerable
Maitland	Warm Temperate Large Temporarily Closed	Vulnerable
Baakens	Warm Temperate Small Temporarily Closed	Least Concern
Papkuils	Warm Temperate Small Temporarily Closed	Least Concern
Swartkops	Warm Temperate Predominantly Open	Vulnerable
Coega (Ngqurha)	Warm Temperate Large Temporarily Closed	Vulnerable
Sundays	Warm Temperate Predominantly Open	Vulnerable
Boknes	Warm Temperate Small Temporarily Closed	Least Concern
Bushmans	Warm Temperate Predominantly Open	Vulnerable
Kariega	Warm Temperate Predominantly Open	Vulnerable
Grant's	Warm Temperate Small Temporarily Closed	Least Concern
Kasouga	Warm Temperate Large Temporarily Closed	Vulnerable
Kowie	Warm Temperate Predominantly Open	Vulnerable
Rufane	Warm Temperate Small Temporarily Closed	Least Concern
Riet	Warm Temperate Small Temporarily Closed	Least Concern
West Kleinemonde	Warm Temperate Large Temporarily Closed	Vulnerable
East Kleinemonde	Warm Temperate Large Temporarily Closed	Vulnerable
Great Fish	Warm Temperate Predominantly Open	Vulnerable
Old Woman’s	Warm Temperate Large Temporarily Closed	Vulnerable
Mpekweni	Warm Temperate Large Temporarily Closed	Vulnerable
Mtati (Mthathi)	Warm Temperate Large Temporarily Closed	Vulnerable
Mgwalana	Warm Temperate Large Temporarily Closed	Vulnerable
Bira (Bhirha)	Warm Temperate Large Temporarily Closed	Vulnerable
Gqutywa	Warm Temperate Large Temporarily Closed	Vulnerable
Ngculura (Ngculurha)	Warm Temperate Small Temporarily Closed	Least Concern
Mtana	Warm Temperate Small Temporarily Closed	Least Concern
Keiskamma	Warm Temperate Predominantly Open	Vulnerable
Nqinisa	Warm Temperate Small Temporarily Closed	Least Concern
Kiwane (Khiwane)	Warm Temperate Large Temporarily Closed	Vulnerable
Tyolomnqa	Warm Temperate Large Temporarily Closed	Vulnerable
Shelbertsstroom	Warm Temperate Small Temporarily Closed	Least Concern
Lilyvale	Warm Temperate Small Temporarily Closed	Least Concern
Ross' Creek	Warm Temperate Small Temporarily Closed	Least Concern
Ncera (Ncerha)	Warm Temperate Large Temporarily Closed	Vulnerable
Mlele	Warm Temperate Small Temporarily Closed	Least Concern
Mcantsi	Warm Temperate Small Temporarily Closed	Least Concern
Gxulu	Warm Temperate Large Temporarily Closed	Vulnerable
Goda	Warm Temperate Large Temporarily Closed	Vulnerable
Hlozi	Warm Temperate Small Temporarily Closed	Least Concern
Hickman's	Warm Temperate Small Temporarily Closed	Least Concern
Buffalo	Warm Temperate Predominantly Open	Vulnerable
Blind	Warm Temperate Small Temporarily Closed	Least Concern
Hlaze (iHlanze)	Warm Temperate Small Temporarily Closed	Least Concern
Nahoon	Warm Temperate Predominantly Open	Vulnerable
Qinira (Quinirha)	Warm Temperate Large Temporarily Closed	Vulnerable
Gqunube	Warm Temperate Predominantly Open	Vulnerable
Kwelera (Kwelerha)	Warm Temperate Predominantly Open	Vulnerable
Bulura (Bulurha)	Warm Temperate Large Temporarily Closed	Vulnerable
Cunge	Warm Temperate Small Temporarily Closed	Least Concern
Cintsa	Warm Temperate Large Temporarily Closed	Vulnerable
Cefane	Warm Temperate Large Temporarily Closed	Vulnerable
Kwenxura (Kwenxurha)	Warm Temperate Large Temporarily Closed	Vulnerable
Nyara (Nyarha)	Warm Temperate Large Temporarily Closed	Vulnerable
Imtwendwe (Mtwendwe)	Warm Temperate Small Temporarily Closed	Least Concern
Haga-haga	Warm Temperate Small Temporarily Closed	Least Concern
Mtendwe	Warm Temperate Small Temporarily Closed	Least Concern
Quko	Warm Temperate Large Temporarily Closed	Vulnerable
Morgan	Warm Temperate Large Temporarily Closed	Vulnerable
Cwili	Warm Temperate Small Temporarily Closed	Least Concern
Great Kei	Warm Temperate Large Fluvially Dominated	Vulnerable
Gxara (Gxarha)	Warm Temperate Large Temporarily Closed	Vulnerable
Ngogwane	Warm Temperate Small Temporarily Closed	Least Concern
Qolora (Qolorha)	Warm Temperate Large Temporarily Closed	Vulnerable
Ncizele	Warm Temperate Small Temporarily Closed	Least Concern
Timba	Warm Temperate Small Temporarily Closed	Least Concern
Kobonqaba (Khobonqaba)	Warm Temperate Predominantly Open	Vulnerable
Nxaxo/Ngqusi	Warm Temperate Large Temporarily Closed	Vulnerable
Cebe	Warm Temperate Large Temporarily Closed	Vulnerable
Gqunqe	Warm Temperate Large Temporarily Closed	Vulnerable
Zalu	Warm Temperate Small Temporarily Closed	Least Concern
Ngqwara (Ngqwarha)	Warm Temperate Large Temporarily Closed	Vulnerable
Sihlontlweni	Warm Temperate Small Temporarily Closed	Least Concern
Nebelele	Warm Temperate Small Temporarily Closed	Least Concern
Qora (Qhorha)	Warm Temperate Predominantly Open	Vulnerable
Jujura (Jujurha)	Warm Temperate Small Temporarily Closed	Least Concern
Ngadla	Warm Temperate Small Temporarily Closed	Least Concern
Shixini	Warm Temperate Predominantly Open	Vulnerable
Beechamwood	Warm Temperate Small Temporarily Closed	Least Concern
Kwazlelitsha (Kwazwedala)	Warm Temperate Small Temporarily Closed	Least Concern
Kwa-Goqo	Warm Temperate Small Temporarily Closed	Least Concern
Ku-Nocekedwa	Warm Temperate Small Temporarily Closed	Least Concern
Nqabara/Nqabarana	Warm Temperate Predominantly Open	Vulnerable
Ngomane (East)	Warm Temperate Small Temporarily Closed	Least Concern
Ngoma/Kobule	Warm Temperate Small Temporarily Closed	Least Concern
Mendu	Warm Temperate Large Temporarily Closed	Vulnerable
Mendwana	Warm Temperate Predominantly Open	Vulnerable
Mbashe	Subtropical Large Fluvially Dominated	Endangered
Ku-Mpenzu	Subtropical Small Temporarily Closed	Vulnerable
Ku-Bhula (Mbhanyana)	Subtropical Small Temporarily Closed	Vulnerable
Kwa-Suku	Subtropical Large Temporarily Closed	Vulnerable
Ntlonyane	Subtropical Large Temporarily Closed	Vulnerable
Nkanya	Subtropical Large Temporarily Closed	Vulnerable
Sundwana	Subtropical Small Temporarily Closed	Vulnerable
Xora	Subtropical Predominantly Open	Vulnerable
Bulungula	Subtropical Large Temporarily Closed	Vulnerable
Ku-Amanzimuzama	Subtropical Small Temporarily Closed	Vulnerable
Nqakanqa	Subtropical Small Temporarily Closed	Vulnerable
Mdikana	Subtropical Small Temporarily Closed	Vulnerable
Mncwasa	Subtropical Large Temporarily Closed	Vulnerable
Mpako	Subtropical Small Temporarily Closed	Vulnerable
Nenga	Subtropical Small Temporarily Closed	Vulnerable
Mapuzi	Subtropical Large Temporarily Closed	Vulnerable
Mtata	Subtropical Predominantly Open	Vulnerable
Thsani	Subtropical Small Temporarily Closed	Vulnerable
Mdumbi	Subtropical Predominantly Open	Vulnerable
Lwandilana	Subtropical Small Temporarily Closed	Vulnerable
Lwandile	Subtropical Large Temporarily Closed	Vulnerable
Mtakatye	Subtropical Predominantly Open	Vulnerable
Hluleka	Subtropical Small Temporarily Closed	Vulnerable
Mnenu	Subtropical Large Temporarily Closed	Vulnerable
Mtonga	Subtropical Large Temporarily Closed	Vulnerable
Mpande	Subtropical Large Temporarily Closed	Vulnerable
Sinangwana	Subtropical Small Temporarily Closed	Vulnerable
Mngazana	Subtropical Predominantly Open	Vulnerable
Mngazi	Subtropical Large Temporarily Closed	Vulnerable
Gxwaleni	Subtropical Small Temporarily Closed	Vulnerable
Bulolo	Subtropical Small Temporarily Closed	Vulnerable
Mtumbane	Subtropical Small Temporarily Closed	Vulnerable
Mzimvubu	Subtropical Large Fluvially Dominated	Endangered
Ntlupeni	Subtropical Small Temporarily Closed	Vulnerable
Nkodusweni	Subtropical Large Temporarily Closed	Vulnerable
Mntafufu	Subtropical Predominantly Open	Vulnerable
Ingo	Subtropical Small Temporarily Closed	Vulnerable
Mzintlava	Subtropical Predominantly Open	Vulnerable
Mzimpunzi	Subtropical Small Temporarily Closed	Vulnerable
Kwanyambalala	Subtropical Small Temporarily Closed	Vulnerable
Mbotyi	Subtropical Small Temporarily Closed	Vulnerable
Mkozi	Subtropical Small Temporarily Closed	Vulnerable
Sikatsha	Subtropical Small Temporarily Closed	Vulnerable
Lupatana	Subtropical Small Temporarily Closed	Vulnerable
Mkweni	Subtropical Small Temporarily Closed	Vulnerable
Msikaba	Subtropical Predominantly Open	Vulnerable
Mgwegwe	Subtropical Small Temporarily Closed	Vulnerable
Mgwetyana	Subtropical Small Temporarily Closed	Vulnerable
Mtentu	Subtropical Predominantly Open	Vulnerable
Sikombe	Subtropical Small Temporarily Closed	Vulnerable
Kwanyana	Subtropical Small Temporarily Closed	Vulnerable
Mtolane	Subtropical Small Temporarily Closed	Vulnerable
Mnyameni	Subtropical Large Temporarily Closed	Vulnerable
Mpahlanyana	Subtropical Small Temporarily Closed	Vulnerable
Mpahlane	Subtropical Small Temporarily Closed	Vulnerable
Mzamba	Subtropical Predominantly Open	Vulnerable
Mtentwana	Subtropical Small Temporarily Closed	Vulnerable
uMthavuna	Subtropical Large Temporarily Closed	Vulnerable
iSolwane	Subtropical Small Temporarily Closed	Vulnerable
iSandlu	Subtropical Small Temporarily Closed	Vulnerable
uMbhoyibhoyi	Subtropical Small Temporarily Closed	Vulnerable
uMuntongazi	Subtropical Small Temporarily Closed	Vulnerable
iKhandalendlovu	Subtropical Small Temporarily Closed	Vulnerable
iMpenjani	Subtropical Large Temporarily Closed	Vulnerable
uMhlangomkhulu (South) (Umhlangankulu)	Subtropical Large Temporarily Closed	Vulnerable
iKhaba	Subtropical Small Temporarily Closed	Vulnerable
iMbizana	Subtropical Large Temporarily Closed	Vulnerable
iMvutshini	Subtropical Small Temporarily Closed	Vulnerable
iBilanhlonhlo	Subtropical Small Temporarily Closed	Vulnerable
uVuzana	Subtropical Small Temporarily Closed	Vulnerable
iKongeni	Subtropical Small Temporarily Closed	Vulnerable
uVunguza	Subtropical Small Temporarily Closed	Vulnerable
oHlangeni	Subtropical Large Temporarily Closed	Vulnerable
iZotsha	Subtropical Large Temporarily Closed	Vulnerable
iBhobhoyi	Subtropical Small Temporarily Closed	Vulnerable
uMbango	Subtropical Small Temporarily Closed	Vulnerable
uMzimkhulu	Subtropical Predominantly Open	Vulnerable
uMthente	Subtropical Large Temporarily Closed	Vulnerable
uMhlangomkhulu (North) (Mhlangamkulu)	Subtropical Large Temporarily Closed	Vulnerable
iDombe	Subtropical Large Temporarily Closed	Vulnerable
iKhoshwana	Subtropical Large Temporarily Closed	Vulnerable
iNjambili	Subtropical Small Temporarily Closed	Vulnerable
uMzumbe	Subtropical Large Temporarily Closed	Vulnerable
uMhlabashana	Subtropical Large Temporarily Closed	Vulnerable
uMhlungwa	Subtropical Large Temporarily Closed	Vulnerable
uMfazezala	Subtropical Large Temporarily Closed	Vulnerable
uMakhosi	Subtropical Small Temporarily Closed	Vulnerable
uMnamfu	Subtropical Small Temporarily Closed	Vulnerable
uMthwalume	Subtropical Large Temporarily Closed	Vulnerable
uMvuzi	Subtropical Large Temporarily Closed	Vulnerable
iFafa	Subtropical Large Temporarily Closed	Vulnerable
uMdesingane	Subtropical Small Temporarily Closed	Vulnerable
iSezela	Subtropical Large Temporarily Closed	Vulnerable
uMkhumbane	Subtropical Small Temporarily Closed	Vulnerable
iNkomba	Subtropical Small Temporarily Closed	Vulnerable
uMuziwezinto	Subtropical Large Temporarily Closed	Vulnerable
uMzimayi	Subtropical Small Temporarily Closed	Vulnerable
Rocky Bay	Subtropical Small Temporarily Closed	Vulnerable
uMphambanyoni	Subtropical Small Temporarily Closed	Vulnerable
aMahlongwa	Subtropical Small Temporarily Closed	Vulnerable
uMahlongwane	Subtropical Large Temporarily Closed	Vulnerable
uMkhomazi	Subtropical Predominantly Open	Vulnerable
iNgane	Subtropical Small Temporarily Closed	Vulnerable
uMgababa	Subtropical Large Temporarily Closed	Vulnerable
uMsimbazi	Subtropical Large Temporarily Closed	Vulnerable
iLovu	Subtropical Large Temporarily Closed	Vulnerable
aManzanamtoti	Subtropical Small Temporarily Closed	Vulnerable
aManzimtoti	Subtropical Large Temporarily Closed	Vulnerable
iZimbokodo	Subtropical Large Temporarily Closed	Vulnerable
iSiphingo	Subtropical Predominantly Open	Vulnerable
Durban Bay	Subtropical Estuarine Bay	Critically Endangered
uMngeni	Subtropical Predominantly Open	Vulnerable
uMhlanga	Subtropical Large Temporarily Closed	Vulnerable
uMdloti	Subtropical Large Temporarily Closed	Vulnerable
uThongathi	Subtropical Large Temporarily Closed	Vulnerable
uMhlali	Subtropical Large Temporarily Closed	Vulnerable
Bob’s Stream	Subtropical Small Temporarily Closed	Vulnerable
uSetheni	Subtropical Small Temporarily Closed	Vulnerable
uMvoti	Subtropical Large Fluvially Dominated	Endangered
uMdlotane	Subtropical Large Temporarily Closed	Vulnerable
iNonoti	Subtropical Large Temporarily Closed	Vulnerable
iZinkwazi	Subtropical Large Temporarily Closed	Vulnerable
uThukela	Subtropical Large Fluvially Dominated	Endangered
aMatigulu/iNyoni	Subtropical Predominantly Open	Vulnerable
iSiyaya	Subtropical Small Temporarily Closed	Vulnerable
uMlalazi	Subtropical Predominantly Open	Vulnerable
uMhlathuze	Subtropical Estuarine Lake	Endangered
Richards Bay	Subtropical Estuarine Lake	Endangered
iNhlabane	Subtropical Estuarine Lake	Endangered
iMfolozi/uMsunduze	Subtropical Large Fluvially Dominated	Endangered
St Lucia	Subtropical Estuarine Lake	Endangered
uMgobezeleni	Tropical Estuarine Lake	Vulnerable
Kosi	Tropical Estuarine Lake	Vulnerable

Download the data here.

Approach

The 2025 assessment of South Africa’s 22 estuarine ecosystem types was conducted using the 2024 IUCN guidelines for red listing ecosystems² and drawing from previous estuarine NBA assessments¹.

The following criterion were assessed:

Criterion A2b (current rate of decline in ecosystem extent); based on land cover change rates between 1990 and 2022 - projected forward to 2040.
Criterion A3 (historical reduction in ecosystem extent), based on land cover 2022.
Criterion B3 was applied to the estuary types that occur at 5 or fewer locations - and for which there is ongoing decline defined as: a) between t1 and t2, fishing pressure shifts from M to H OR H to VH, OR b) PES class A, B and C extent declined by >1%, OR extent of H and VH Fishing pressure at year of assessment is greater than 30% of type extent. This captures increasing or sustained gill-netting pressures, and steady decline in ecosystem condition as triggers. The rating applies to the whole type and is scaled by estuarine extent.
Criterion D1 was applied using fishing pressure scores for each estuary. The scores were converted to an index 0-1 and aligned to severity rating (1 highest severity - 100%; 0 lowest severity - 0%). The rating applies to the whole type and is scaled by estuarine extent.
Criterion D3 was applied to the Estuarine Ecological State Class (PES) data such that severity of biotic disruption of >= 90% was assumed for PES classes E-F; Severity >=70% was assigned to PES classes D-F; Severity >=50% was assigned to PES classes C-F. The rating applies to the whole type and is scaled by estuarine extent.

Each of the 22 estuary ecosystem types were assigned to one of the four risk categories: Critically Endangered, Endangered, Vulnerable and Least Concern. The highest risk category for the criteria was selected as the threat / risk status for each river type.

A more detailed explanation of the assessment method can be found on the about ecosystem threat status page.

Technical documentation

Code repositories

Skowno, A.L. 2025. SANBI-NBA Estuary ecosystem threat status [Source code]. GitHub repository available at https://github.com/askowno/RLE_est.

Key publications

Rowland, J.A. et al. 2020. Ecosystem indices to support global biodiversity conservation. Conservation Letters 13, 11. https://doi.org/10.1111/conl.12680

IUCN. 2024. Guidelines for the application of IUCN Red List of Ecosystems. Gland, Switzerland. https://doi.org/10.2305/CJDF9122

Recommended citation

Van Niekerk, L., Skowno, A.L., Sink, K., & Harris, L.R. 2025. Ecosystem threat status: Estuarine realm. National Biodiversity Assessment 2025. South African National Biodiversity Institute. http://nba.sanbi.org.za/.

Refernces

1. Van Niekerk, L. et al. 2018. Chapter 8. Ecosystem threat status and protection levels. South African National Biodiversity Assessment.

2. Keith, D.A. et al. 2024. Guidelines for the application of IUCN red list of ecosystems categories and criteria (version 2.0).