Heinsia crinata, the most spectacular of the flowering shrubs.
Blossoms of mbambakofi (Afzelia quanzensis), a hardwood tree much valued by Lamu woodworkers for traditional furniture, doors etc.
Psychotria punctata, one of the favourite nectar sources for coastal butterflies.
Growing a backyard forest The story of a coastal woodland that was grown from scratch
M By Will Knocker
any of the most valuable timber species take many years – often more than a single person’s lifetime to mature. The destruction of a forest, then, is very tragic indeed, because that forest can never be replaced as it is, especially in terms of its mature trees, some of which might be hundreds of years old. It is against this background, and with the ongoing destruction of many of Kenya’s forests, that I would like to tell the story of a forest that has been grown from scratch. My father, Roddy Knocker, bought a beach plot at Watamu at the coast, in 1963. The original owners had bought the plot in the 1950s and had cleared it of “bush” to mark out their property in what was then a veritable ocean of “bush”. How things have changed! Almost 50 year later, the “ocean of bush” has given way to property developments which threaten to eliminate the “bush” altogether! Beach plots at Watamu are about as unfavourable to tree-growing as you can imagine. Soil consists of thin red sand, the product of broken down limestone from ancient coral reefs. There are essentially two seasons – a wet season (kusi) lasting from April (if lucky) to August, and a long very hot season (kaskazi) from September to March which often causes major water stress to vegetation. My father planted coconuts on the plot in the 1960s and the trees were mature when my parents
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retired to the coast in 1980. That same year, my father decided to let the natural vegetation return whilst at the same time beginning an intensive planting of trees in each rainy season (May). The main challenge was to create the conditions - and especially topsoil (humus) - to enable a forest to grow. This could only be achieved over the long term, echoing René Haller’s famous experiment in a similar coral-rag environment at Haller Park, Bamburi. Our plot is an interesting one, positioned as it is on the seafront and going back to a seasonal rain pan associated with Mida Creek at the back, so going from sea level, transecting dunes, which have built up over an old reef, to sea level again at the back, along the main road. We have seen some interesting changes to the various eco zones that exist on the plot. These are the ocean foreshore, a fearsomely salty zone right next to the high water mark; and the dune sector above the beach, where trees grow most easily owing to the water held in the sand. Then there is the dry coral rag bush zone behind the dunes and the wetland, with a high but saline water level adjacent to the main road to the west. The foreshore, consisting of white beach sand, the remains of millennia of molluscs and coral polyps crushed by the sea and bleached white by the wind and sun, has twice increased by at least 50 metres, the most recent event having been after the tsunami of 2005. Each time, the foreshore has
been colonised quickly by pioneer, necessarily saltresistant species such as casuarina and coconut. My father planted a barrier of casuarinas in the 70s, when we first “gained” beach, to protect the wind-swept dunes behind from salt spray generated at high spring tides. A very interesting variety of Indo-Pacific foreshore plants are found here, including Scaevola, Pandanus kirkii, Guettarda, Sophora, Thespesia populnea and Hibiscus tiliaceus, some of which were planted. However, high rainfall species, such as takamaka (Callophyllum inophyllum) from the Seychelles, quickly dried up and died in the dry conditions. On the dunes behind the beach, one finds classic evergreen dune-forest consisting of species such as Pycnocoma littoralis and Drypetes natalensis. These grew up well in the lee of the wind/salt barrier created by the wonderful Casuarina, which are not only salt tolerant (exuding salt solution from their leaflet ends) but also fix atmospheric nitrogen through a bacteria that grows in symbiosis with their root nodules. Behind the dune top, large trees grow well protected from the salty sea winds and feeding from underground moisture trapped in the dunes. Here grow Afzelia quanzensis – an important timber tree at the coast as its wood is used in the building of dhows, Mimusops obtusifolia, Drypetes reticulata and Tamarindus indica as well as doum palms –Hyphaene compressa. This eco-zone was largely
Miti July-September 2010