Written by Sandra Dell & Zoë Poulsen. Photos by Tony Dickson
Above: The group gathers at the Beachwood Mangroves Nature Reserve lapa.
On Saturday 3 August the BotSoc KZN Coastal Branch visited Ezemvelo KZN Wildlife’s Beachwood Mangroves Nature Reserve on a guided walk to learn more about this extraordinary ecosystem. The visit was led by aquatic scientists Professor Ticky Forbes and Nicolette Forbes from consultancy Marine and Estuarine Research (MER). The group was also kindly accompanied by the Beachwood Honorary Officers. The reserve’s lapa and parking area will be the same venue for the BotSoc branch’s indigenous plant fair to be held on 7 & 8 September.
Above: Nicky Forbes reveals the wonders of the intertidal zone and the mangroves that are adapted to thrive there.
Beachwood Mangroves Nature Reserve is one of Durban’s hidden gems. The reserve is normally closed to the public except by appointment but opens on the third Saturday morning of each month for guided walks led by the Honorary Officers. A boardwalk trail through the reserve allows easy access for visitors. Located at the Umgeni River mouth in Durban North, it is one of the last protected fragments of mangrove habitat on the KZN coastline. Mangrove forest is classed as ‘Critically Endangered’, with much of its original extent lost as a result of harbour development, urban development and degradation through unfavourable agricultural practices inland.
Above: A Grey Heron arrived and we eyed each other out.
Mangrove forest is found along South Africa’s eastern coastline where it is warmed by the Mozambique current from Kosi Bay southwards to Nahoon Estuary. This ecosystem forms between mean sea level and mean high water spring tide level in sheltered estuaries on tidal flats. The soils on which they grow are saline and fine grained with poor drainage and high organic content. Mangroves protect the shoreline against extreme weather, stabilise the shoreline and provide a vital habitat for their fascinating flora and wildlife.
Above: The Beachwood Honorary Officers kindly accompanied us. They lead walks during a monthly open day on the 3rd Saturday morning of each month.
There are three different mangrove species present in the Umgeni estuary, each one with its own unique adaptations for eliminating salt. As the scientific name suggests, the Red Mangrove (Rhizophora mucronata) has a ‘mucro’ or needle-like point on the leaf tip. The roots are extensive prop roots of up to 30 metres that anchor and stabilise the tree despite its relatively diminutive height. Red Mangrove Crabs feed on the leaves of this species, collecting the dropped leaves and taking them down their burrows for food.
Above: Red Mangrove Crab collecting fallen leaves for food.
The Black Mangrove (Bruguiera gymnorrhiza) has stabilising buttress roots and underground cable roots. The cable roots loop upwards to form knee roots for taking in oxygen. Nutritive roots also lead from the cable roots into the mud. The White Mangrove (Avicennia marina) is a primary coloniser that allows the other two mangrove species that are found here to grow. Its root system is extensive and consists of shallow, horizontal cable roots with pencil roots (also known as pneumatophores) growing upwards and above ground in fine sediment and when the ground is waterlogged, allowing the tree to breathe.
Above: Here erosion has exposed more of a Black Mangrove’s root system than we might normally see.
Another plant that was seen was the Matting Rush (Juncus kraussii). This plant is in demand in the wild for material used for making sleeping mats. The group also stopped to observe the antics of male Fiddler Crabs with their comical enlarged single orange claws. They may be either left or right ‘handed’, waving their claws to attract females. Different species have different waving patterns.
Above: Matting Rush (Juncus kraussii).
After arriving back at the lapa, Nicolette Forbes showed the group some historical aerial photographs of the reserve. Interestingly these showed that the site now has far more mangroves present than there were in the 1930s. Four dams that have since been built have meant that there are no longer strong river flows, thus allowing more shallow sandbanks to form and hence mangroves to grow.
Above: Male Fiddler Crab.
The KZN Coastal Branch would like to thank Ticky and Nicolette Forbes for a wonderful outing. The Forbes gave patient explanations on many complex subjects around mangrove ecosystems. For more information, please see their recent update of the WESSA handbook, ‘In the Mangroves of Southern Africa’. Thank you too to the reserve’s Conservation Manager Basil Pather, the Ezemvelo KZN Wildlife staff and Honorary Officers for all of their assistance.