This is the most recent version of the National Estuary Ecosystem Map. The map was developed as a collaborative effort and delineates the Estuarine Functional Zone for South Africa (Van Niekerk et al. 2019a). Each EFZ was then assigned an ecosystem type according to Van Niekerk et al (2019b).

In South Africa, the EFZ is defined as the area that not only encapsulates the estuary waterbody, but also the supporting physical and biological processes necessary for estuarine function and health. It includes all dynamic areas influenced by long-term estuarine sedimentary processes, i.e. sediment stored or eroded during floods, changes in channel configuration, aeolian transport processes, and/or changes due to coastal storms. It also encompasses the multiple ecotones of floodplain and estuarine vegetation that contribute detritus (food source) to the estuary and/or provide refuge during high flow events. The EFZ captures the natural, historical estuarine extent and should not be confused with setback/management lines that often exclude developed areas. The EFZ purpose is to identify the ‘space’ in which estuarine physical and biological functions take place over long time scales (>decades). Development in the EFZ is captured as an aspect of habitat degradation or decline in overall estuary condition.

The upstream boundary of the estuaries was determined as the limits of tidal variation or salinity penetration, whichever penetrates furthest. The estuary mouth was taken as the downstream boundary of an estuary. The highly dynamic nature of this area presents a significant challenge to accessing change in biodiversity and even managing estuaries. To account for this, and to allow for a seamless integration with the Marine and Coastal Realm, the concept of ‘Estuarine Shore’ was introduced to reflect the dynamic nature of the interface between estuaries and the coast. Estuarine Shores refers to sand berms or bars that form in front of estuaries. They vary substantially in size and shape over decadal scales and can be completely absent during a flood or a near permanent feature during periods of low flow. Estuarine Shore was defined as the area from the base of the foredune, or where this line would be if dunes were present, to the back of the surf zone. The full extent of the Estuarine Shores is encapsulated in the EFZs and not be considered separate from the functional unit. The surfzone was included to reflect a continuum in estuarine-marine connectivity through estuarine inputs to the surfzone, either as direct flow through an open mouth or in seepage through the berm in a closed system.

In total 290 estuaries and 42 micro-estuaries were delineated and classified into 22 estuary ecosystem types and 9 micro-system types. The estuary classification is based on 4 biogeographical regions (Cool Temperate, Warm Temperate, Subtropical and Tropical) and 9 estuary categories (Estuarine Lake: Estuarine Bay, Estuarine Lagoon, Predominantly Open, Large Temporarily Closed, Small Temporarily Closed, Large Fluvially Dominated, Small Fluvially Dominated, Arid Predominantly Closed). While the micro-estuary ecosystem classification is derived from one micro-system type across 3 biogeographical region.