Assessment of the conservation priority status of South African estuaries for use in management and water allocation

Abstract

The future health and productivity of South Africa's approximately 250 estuaries is dependent on two main factors: management and freshwater inputs. Both management and water allocation decisions involve trade-offs between conservation and various types of utilisation. In order to facilitate decision-making in both of these spheres, it is necessary to understand the relative conservation importance of different estuaries. This study devises a method for prioritising South African estuaries on the basis of conservation importance, and presents the results of a ranking based on the collation of existing data for all South African estuaries. Estuaries are scored in terms of their size, type and biogeographical zone, habitats and biota (plants, invertebrates, fish and birds). Thirtythree estuaries are currently under formal protection, but they are not representative of all estuarine biodiversity. We performed a complementarity analysis, incorporating data on abundance where available, to determine the minimum set of estuaries that includes all known species of plants, invertebrates, fishes and birds. In total, 32 estuaries were identified as 'required protected areas', including 10 which are already protected. An estuary's importance status (including 'required protected area' status) will influence the choice of management class and hence freshwater allocation under the country's new Water Act, and can be used to assist the development of a new management strategy for estuaries, which is currently underway.

Classifying Ecological Quality and Integrity of Estuaries

“…The FIR has been applied to estuaries spanning the entire South African coast. Turpie et al (2002) assessed the conservation priority of South African estuaries using a number of attributes, which included estuarine size, rarity of estuarine type, habitat diver sity, and biodiversity in terms of plants, invertebrates, fish, and birds. The biodiversity component was restricted to a species rarity measure for each biotic component.…”

“…The biotic components include microalgae, macrophytes, invertebrates, fish, and birds; this comprises measures of species richness, abundance, and com munity composition for each group. The present ecological status is defined by six categories (A-F), each representing a broad degree of deviation from reference (natural) conditions (A) and where a highly degraded system would be classified in category F. Estuary importance is established following the procedure developed by Turpie et al (2002), which includes measures of estuarine size, estuarine type rarity, habitat diver sity, biodiversity importance, and functional importance. The ecological management class represents the desired future condition of an estuary and is based on a combination of estuarine health and importance (DWAF, 1999).…”

Effects of prolonged elevated water salinity on submerged macrophyte and waterbird communities in Swartvlei Lake, South Africa

“…Climate change and resulting changes in the marine environment, such as sea level rise and increased hydrostatic, wave and wind set-up, will affect estuaries in several ways, including increased intrusion of seawater (Theron and Rossouw, 2008). Although pollen analysis of the adjacent Groenlvlei Lake sediments provides some evidence to suggest that global cooling is associated with drier conditions in the southern Cape (Martin, 1968), and hence by default global warming is associated with wetter conditions, climate change models widely forecast increases in the intensity and frequency of droughts in South Africa resulting from global warming (Cook et al, 2014;Dia, 2013), with only the eastern subtropical portions of the country likely to experience generally wetter conditions (Engelbrecht et al, 2009;Shongwe et al, 2009;Tadross et al, 2005).…”

“…What estuarine lakes lack in number, however, they make up for in size, collectively comprising more than 62% of estuarine area in the country (Van Niekerk and Turpie, 2012). Most have a high conservation value, with 5 of the 8 ranking in the top 10 estuaries in South Africa in terms of conservation importance, and with 7 of the 8 in the top 40 (Turpie et al, 2002). The Swartvlei system ranks 7 th .…”

Lake St Lucia, Africa’s largest estuarine lake in crisis: Combined effects of mouth closure, low levels and hypersalinity

“…This is of concern, as the St Lucia estuary is one of the most important estuaries in South Africa. 17,29 The lack of a connection to the sea during the study, coupled with major changes and fluctuations in the physical conditions within the system, have also had an impact on the offshore marine ecosystem where a lack of recruitment over a 5-year period could affect the breeding stock of marine species whose life cycles are associated with estuaries. This has already been shown for the marine spawning fish R. sarba.…”