The mangroves of South Africa: An ecophysiological review

Abstract

Mangroves are unique, highly productive forests that interface between marine and terrestrial environments in protected and sheltered habitats of tropical and temperate regions. In Africa, mangroves reach their southern distributional limit in the warm temperate zone at Nahoon Estuary (32°56′ S) in South Africa. Temperate mangroves are less diverse, slower growing and of smaller stature than those in the tropics. This review gives an overview of mangrove distribution in South Africa and factors that constrain their spread. This is followed by an ecophysiological overview of mangrove adaptations to survive in an intertidal environment characterized by heterogeneous salinity, waterlogging and low nutrients. These adaptations play critical roles in salt exclusion, maintenance of low tissue water potentials and conservative water and nutrient use. Adaptations range from macro to micro levels and include root, stem and leaf morphology. It also discusses characteristics of mangroves at higher latitudes that distinguish them from their tropical equivalents. The effects of anthropogenic pollution, climate change and sea level rise, as well as local threats in South Africa are also discussed. This review also includes a detailed list of research conducted on South African mangroves and makes suggestions for future work.