PLANT BIODIVERSITY AND ETHNOBOTANICAL APPLICATIONS IN TWO KAYA FORESTS IN KILIFI COUNTY

Abstract

The sacred Kaya Kauma and Tsolokero forests in Kenya's Kilifi county are under the management of a council of elders and are gazetted as National Monuments. Eight out of the more than 52 Kaya forests are designated UNESCO heritage sites. The forests sustained and protected by traditional customs are under threat from settlement and development, yet the status of the rich plant diversity and its relationship to the communities is not known. A study was conducted to document the ethnobotanical knowledge on useful plants among forest adjacent communities, assess the diversity of useful plants in the sacred Kaya forests and determine the efficacy of selected medicinal plants on the most prevalent diseases in the study areas. The study targeted the general population, the sacred Kaya council of elders and herbalists. A semi-structured questionnaire was administered to document knowledge of useful plant species on the basis of gender, age, marital status, level of education, main occupation and their relationship to the village. The data was then analysed using Kruskal-Wallis H Test using SPSS Statistics. The diversity of useful plants was assessed across quadrants along four transects in the sacred Kaya forests. Species richness, abundance, evenness and Shannon-Wienner index of diversity were calculated. Additionally, the frequency, density and abundance of useful species in the forest was calculated using formula by Cottam and Curtis (1956) and frequency classes assigned to species. A bioassay using herbalists’ formulations of eleven medicinal plant species reported to treat conditions commonly associated with bacterial infection were validated for their efficacy in laboratory. Maps of the study areas were generated for the first time designating the forests and the associated adjacent villages. Only 7 out of the 9 Mijikenda communities resided around the two forests in different compositions with the Kauma and Chonyi the most knowledgeable in useful plants in Kaya Kauma and Kaya Tsolokero respectively. A demographic survey on indigenous knowledge of useful plants indicated significant (P<0.05) differences in knowledge with age and marital status on food plants; population with no formal education was significantly knowledgeable on medicinal plants; and teachers were significantly vi (p<0.05) informed on fuelwood plants. At Kaya Tsolokero, the adults were significantly (p<0.05) knowledgeable on medicinal plants while the youth were knowledgeable on constructional plants. Documenting plants in local language overestimated the number of plants to 404 with taxonomic validation reducing the number to 319, with only 45 common to both Kaya sites. The herbalists mentioned 91 medicinal plants species associated with treatment of pulmonary and cardiac, circulatory, gastrointestinal, dermatological, body pains, pest infection, gynaecological, urinary, fever, neurological, antidote and treatment of livestock conditions. Among the species mentioned by the community 13 and 15 are endemic to coastal Kenya, 36 and 44 are exotic, and 10 and 13 are listed in IUCN Red List as threatened at Kaya Kauma and Tsolokero sites respectively. A high proportion, 53 -95%, of useful plants for all categories was documented as both commercialised and domesticated. The forests are distinct and almost homogenous and heterogeneous in useful plant communities at Kaya Kauma and Kaya Tsolokero respectively with a total documented at Kaya Kauma 51at and Kaya Tsolokero 70 useful plant species. The diversity measures; species richness, species evenness, species abundance and Shannon-Wienner index of diversity were highest at Kaya Tsolokero. Whereas, frequency indicated 65% of the useful species as least frequent (0-20%), extremely low in abundance, and patchily distributed in both forests. Only few species were widespread, with only 6% of the species most frequent (80-100%) at Kaya Kauma and only 2% moderately frequent (40-60%) at Kaya Tsolokero forests. Out of the species documented, 17% and 23 % species are endemic, 9% and 12% exotic, 13% and 10% are IUCN Red Listed as threatened species in Kaya Kauma and Kaya Tsolokero respectively and 2% species are rare in Kaya Kauma. Finally, a bioassay of eleven medicinal plants in the formulations used by herbalists assessed in the laboratory indicated eight species to have activity against Staphylococcus aureus and Escherichia coli. The study indicates ethnobotanical knowledge on useful plants still exists among forest adjacent communities, although under threats, the forest plant species diversity is high and of significance to the communities, however, there is a critical decline in the populations of individual species. The community is highly vii dependent on herbal medicines for health care, hence presenting a high for bioprospecting for novel remedies. There is however need to address the loss in indigenous knowledge which is core to conservation of the forest and also develop strategies