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Home , Ceriops tagal, Mangrove

A note on the distribution and approximate areas of in

C.J. Ward and T.D. Steinke Department of Botany, University of Durban-Westville, Durban

The occurrence of individual , of which there are five Introduction in South Africa, and the approximate total area of mangroves in all known South African estuarine systems are presented For an assessment of the importance of mangroves in the for the first time for South Africa as a whole. Natural in­ ecology of , information on their occurrence and crease is occurring throughout the region although this is extent is essentiaL To date detailed information has not masked in many places by the direct destruction of the mangroves themselves or through adverse effects on their been available. Macnae (1963) selected only a few estuaries habitats. for description, whereas Berjak et al (1977) listed only the S. Afr. J. Bot. 1982, 1: 51-53 larger known . The distribution shown by Mollet a/ (1971) was more complete, but it is now out Die voorkoms van individuele spesies, waarvan daar vyf in Suid-Afrika is, asook nagenoeg die totale gebied waarin of date and no indication of areas was given. Furthermore, mangliete in Suid-Afrikaanse estuariese sisteme voorkom, with the exception of the work by Steinke (1972), Steinke word vir die eerste keer vir Suid-Afrika as geheel aangebied. & Ward (1973) and Ward (1980), there has been no infor­ Natuurlike aanwas kom oor die hele gebied voor, alhoewel dit op verskeie plekke verbloem word deur direkte uitwissing van mation published recently on the distribution of individual die plante self, of deur faktore wat hulle habitat nadelig mangrove species in this country. To provide these details be·invloed. a survey of all known estuaries with mangroves was con­ S.-Afr. Tydskr. Plantk. 1982, 1: 51-53 ducted using aerial photography. The following is intend­ ed as a preliminary note giving basic species distributions Keywords: mangroves, , South Africa and community areas for mangroves in South Africa.

Methods Aerial photographs, and orthophotographs of the coastline supplied by the Trigonometrical Survey Office, were used in this survey. The scale of the photographs ranged from 1:10 000 to 1:60 000 and, wherever possible, the largest scale and most recent records were used. Although measurements were made from aerial photographs, local photograph scale was checked against the standard l :50 000 topographical sheets for South Africa, or against l: l 0 000 orthophotographs where these were available. With the exception of two estuaries, Mzintlava and Mten­ tu, all mangrove communities have been visited by one or both of the authors in recent years and all have been observed from the air.

Observations Mangrove communities occur from the Kosi System (26°54'S) to the Nahoon River (32°59'S) (Figure 1). The figure also shows the areas under mangrove and the species present. The total area is approximately I 058 ha of which Natal has 785 ha, followed by Transkei and eastern Cape with 272 ha and l ha respectively. There are five species of mangroves present in this area. tagal (Perr.)

C.J. Ward* and T.D. Steinke C. B. Robinson and racemosa Willd. occur on­ Department of Botany, University of Durban-Westville, ly in the Kosi System with C. tagal present only in the lower Private Bag X54001, Durban 4000, Republic of South Africa , while L. racemosa extends to the upper limits of *To whom correspondence should be addressed the estuarine section of the System. mucronata Accepted 16 April 1982 Lam. occurs discontinuously from Kosi to the Bulungula 52 S.-Afr. Tyd skr. Plantk. 1982, 1(3)

30° , MOCAMBIQUE ·--..../·· -..... - ~ -- - ·· - ·· - -· - -· - -- Kosi (59,0 ..... 60)

· -~ · } ENLARGED SECTION

KEY Richards Bay (427,5 ..... ) Figure represents approximate area in ha 'Y marina e gymnorrhiza • 6 0

30°

0 20 40 60 80 100 1\ m

- Mtakatye(7,5'Ye•) ~ Mdumbi(l,O 'Y) Mtata(34,0 "Ye •) Bulungula(3,5 "Ye •) -----...... _ Xora(l6,0'Yel -...... Mbashe( 12,5 'Y e l Nqabara/ Nqabarana(9,0 'Yl

Nxaxo/ N gqusi(l4,0 'Y e l "- Kobonqaba(6,0 'Yl Kwelera( <0,5 'Yl >'-.L----Gqunube( <0,5 'Y) Nahoon(0,5 'Y e l

Figure 1 Distribution and approximate areas of mangroves in South Africa. S. Afr. J. Bot. 1982, 1(3) 53

River. Bruguiera gymnorrhiza (L.) Lam. extends as far have been increasing steadily in recent years. However, south as the Nxaxo-Ngqusi Rivers, dominating the later destruction of mangroves in this country, as in happening stages in mangrove succession and occurring where elsewhere, has been fairly extensive in the recent past and are low or water level fluctuations are reduced. is still continuing. Evidence is available of the importance A vicennia marina (Forsk.) Vierh. occurs throughout the of healthy estuarine communities for area except in those systems where tidal influence is reduced (Lear & Turner 1977; van der Elst 1977), therefore the con­ and where the water is often of low . sequences of the loss of mangrove and other plant com­ munities are viewed with concern. Discussion Mangroves are more common than has been claimed in the Conclusion past (West 1944; Macnae 1963). The extensive communities If natural establishment continues along the and also are at Richards Bay, St Lucia, Mngazana and Kosi, within estuaries, it is possible that mangroves in the future although well developed communities occur in many other will become more widespread than they are at present. estuaries as well. Mangroves have a significant role to play Alternatively, continued destruction will reduce the pre­ in the ecology of these estuaries. The nature and extent sent area under mangroves. Whatever the circumstances, of the contribution of mangroves towards the productivi­ regular re-assessments of these estuarine communities are ty of these ecosystems is presently under investigation. desirable. South of the Kei River mangroves are of little impor­ tance as estuarine communities. It is pointed out that the Acknowledgements mangroves on the Nahoon River were established by the The Council of the University of Durban-Westville as well second author with material transplanted from Durban Bay as the Natal Town and Regional Planning Commission, and are not a naturally established community. Growth the Natal Parks Board and the Wildlife Society of Southern has been good which indicates that unfavourable climatic Africa are thanked for contributions made towards the conditions, at least since their establishment in 1969, can­ gathering of field data while the kind co-operation of Mr. not be regarded as the main factor responsible for the R. Sookrajh in preparing the map is gratefully paucity of the mangroves in this area. This view is acknowledged. strengthened by the fact that in A. marina is found at a latitude of 38°45'S where climatic conditions References are less favourable for growth of mangroves than in the BERJAK, P ., CAMPBELL, G.K., HUCKETT, B.!. & eastern Cape (Wells 1980). In addition to the monitored PAMMENTER, N.W. 1977. In the mangroves of Southern introductions at Nahoon, there are reports of indiscrimi­ Africa. Durban, Wildlife Society of Southern Africa (Natal nate planting of mangroves in that general vicinity of the branch): I - 72. eastern Cape. Other planting has taken place in Natal; and LEAR, R. & TURNER, T. 1977. Mangroves of Australia. Univ. of Press: I - 84. this has mostly had the effect of increasing numbers of in­ MACNAE, W. 1963. Mangrove swamps in South Africa. dividuals of species already present. The few small in­ 1. Ecol. 51 : 1-25. dividuals of A. marina present at Msimbazi, however, MOLL, E.J., WARD, C.J., STEINKE, T.D. & COOPER, K.H. represent an artificial establishment in a system which, 1971. Our mangroves threatened. Afr. Wildlife 25 : 103 - 107. under purely natural conditions, is unlikely to have sup­ STEINKE, T.D. 1972. Further observations on the distribution of mangroves in the Eastern Cape Province. 11 S. Afr. Bot. ported the continued presence of this species. The record 38 : 165 - 178 . of R. mucronata at Mlalazi is included here although there STEINKE, T.D. & WARD, C.J. 1973 . Ceriops tag a I (Perr.) C.B. are only two small specimens both introduced artificially Rob. at , 11 S. Afr. Bot. 39: 245-247. in recent years. Omitted from the distribution map are VANDER ELST, R. 1977. The economic importance of the those mangroves introduced into the Beachwood arm of mangrove community: its associated aquatic fauna and the mangrove . In: In the mangroves of Southern Africa. the Mgeni estuary which are considered to be quite foreign Durban Wildlife Society of Southern Africa (Natal branch): to that locality. These were introduced for academic and 69-71. education purposes and are being carefully monitored; they WARD, C.J. 1980. The plant ecology of the Isipingo area. include C. tagal and L. racemosa from Kosi Estuary as Mem. bot. Surv. S. Afr. 45: I - 147 well as a few Australian species. WELLS, A.G. 1980. Distribution of mangrove species in Australia. In: Proc. Second InternaL Symp. Bioi. Mgmt. Mangroves, From observations made of many of the estuaries over (In press). a period of time it appears that, where there has been WEST, 0 . 1944. Distribution of mangroves in the eastern Cape relatively little interference, the mangrove communities Province. S. Afr. 1. Sci. 41: 238-242