Indigenous knowledge and local vegetation categories
People of the study area classify vegetation of their surroundings mainly based on density of plant species that cover the land. The following four categories of vegetation were used by the community to distinguish one vegetation type from another. They then describe the location of a medicinal or other useful plant distribution in terms of these categories.
‘Caffee’ is marshy vegetation where mostly plant species of the families Poaceae and Cyperaceae grew. The place is generally considered unsuitable for ploughing and crop cultivation but is suitable for grazing.
‘Luugoo-lagaa’ is equivalent to reverine vegetation which is found at the banks of rivers, mostly composed of Syzygium guineense subsp. guineense and Ficus sycomorus.
‘Bosona’ is a type of forest with densely populated plant species with many tall trees, making the home of wild animals. An example of such vegetation in the study area is ‘Bosona Komto’ (Komto Forest), which is found in Komto Kebele.
‘Daggala’ is the term used to refer to seasonal plants.
Medicinal plants of the study area
One hundred twenty six species, belonging to 108 genera and 56 families, were used by local people of the District to treat various human and livestock ailments (Tables 1, 2 and 3). There were seven endemic species of Ethiopia found among the reported traditional medicinal plants (Albizia malacophylla, Coccinia abyssinica, Impatiens tinctoria subsp. abyssinica, Lippia adoensis, Pycnostachys abyssinica and Saturegia paradoxa). Among the families that contributed more medicinal species were the Fabaceae, represented by 15 species (12%), Solanaceae with 8 (6.3%) species, Asteraceae with 7 (5.6%), and other 44 families contributing 57 (45%) species are represented by 1 or 2 species (Table 4). Of the 126 species of medicinal plants collected from the study area, most of them (86, 68%) were obtained from the wild whereas 33 (26%) were from homegardens, and only 7 (5.5%) species were from both homegardens and wild habitats (Tables 1, 2 and 3).
The result of growth form analysis of medicinal plants showed that herbs constituted the highest proportion being represented by 55 (43.6%) species, while there were 34 (27%) tree species, 26 (20.6%) shrubs and 3 (2%) lianas (Figure 3).
Informants of the study area harvest different plant parts for preparation of traditional drugs (e.g. leaves, roots, seeds, barks and fruit). In the study area, the informants reported that more species (70, 43%) of medicinal plants were harvested for their leaves and these were followed by roots (30, 18.5%), seed and bark (18, 22.2%) each and 26 others (bulb, tuber, stem, fruit and flower) covered 16% (Figure 4).
Among the collected 126 medicinal plant species, 78 (62%) were claimed to treat human health problems (Table 1), 23 (18.2%) were claimed to treat livestock ailments (Table 2) and 25 (20%) were for both human and livestock ailments (Table 3).
People of the study area mostly administer traditional medicine orally. This accounted for 64%, followed by dermal administration (27.3%) and others (nasal, anal, optical, ear) accounting to 8.3%. Local people also reported that various additives were given during administration of traditional medicine.
Condition, dosage and effectiveness of traditional medicine in the study area
The majority of the remedies (74.2%) in the study area were prepared from fresh parts of medicinal plants followed by dried form (20.7%) and (5%) prepared either from dry or fresh plant parts. Most of the medicinal plant preparations involved the use of single plant species or a single plant part (85%) while those mixing different plants or plant parts (15%) were rarely encountered in the study area. Healers, usually prepare remedies by mixing various plants or plant parts. Lack of consistency regarding amount of medicines to be used was observed among informants during the interview.
Local people of the study area used various ways of measuring dosage which were generally categorized under three major classes. One is dosage used for those medicinal plants which are expected to be highly toxic. For such medicines the measurement was undertaken by little finger index and very few amounts of the prepared medicine taken by a cup of coffee (Locally known as ‘Sinii’). For example, medicines prepared from Phytolacca dodecandra, Cucumis ficifolius, Carissa spinarum and Securidaca longepedunculata are toxic if overdosed. The second is the dosage used for medicinal plants which can have little effect. The dosage is measured by hand palm and taken by bottle or locally made material from Lagenaria siceraria known as ‘Hullee’. E.g., traditional medicines prepared from Vernonia amygdalina. In the third case there are medicinal plants that do not have any observable side effect. Medicines prepared from Allium sativum, Citrus limon, and Citrus aurantium can be taken according to personal preference of the patient. Moreover, informants indicated the effectiveness of traditional medicines to get relief from certain diseases including rabies and health problems associated with the liver, spider poisoning and those caused by bat urine.
Methods of preparation of traditional medicine
In the study area, the most common methods of preparation of traditional medicine from plant material was crushing (29%), followed by powdering (28%) and others (Table 5).
Importance of medicinal plants in the study area
Paired comparison ranking of 7 medicinal plants that were reported as effective for treating blackleg, was conducted after selecting 9 informants. The informants were asked to compare the given medicinal plants based on their efficacy. The results showed that Cucumis ficifolius scored the highest mark and ranked first indicating that it was the most effective in treating blackleg and followed by Lepidium sativum (Table 6).
Direct matrix ranking of multipurpose medicinal plants
Among the medicinal plants reported by the informants, there were those that were used for other purposes and thus grouped as multipurpose species. Key informants first identified eight medicinal plant species that were used by the community for additional purpose including fire wood, charcoal making, construction purposes, food, fencing and forage. Application of direct matrix ranking to these species showed that Cordia africana was the best, followed by Eucalyptus globulus and Crotom macrostachyus (Table 7).
Informant consensus factor (ICF)
The result showed that, diseases that were frequent in the study area have higher Informant Consensus Factor. Medicinal plants that are effective in treating certain disease and well known by community members also have higher ICF. Malaria and headache had the highest ICF value (0.85) whereas, Rabies had the lowest ICF value (0.25) (Table 8).
Threats to medicinal plants and conservation practices in the study area
In Wayu Tuka District various factors that were considered as main threats for medicinal plants were recorded by discussion with the informants. Accordingly, the major factors reported were deforestation for the purpose of agricultural expansion (75%), overgrazing (10%), collection of plant material for construction (10%) and fire wood (5%).
People of the study area know the benefits of conserving medicinal plants. However, the effort of conserving medicinal plants is very limited (minimal). That is an evident for being only 26% of medicinal plants were collected from homegarden. Local healers who frequently make use of medicinal plants for a living do not conserve medicinal plants very well, and they preferred to collect them from wild stands when patients visit them. It was explained by informants that local healers do this in order not to let the other community members know the identity of the medicinal plants they are using. Informants further explained that if healers planted the species in their homegardens, they suspect that somebody else might see them while they are preparing the medicine from the plants and start to prepare them and reduce the income which could have gone to the healer. Further observations showed some medicinal plants frequently growing in homegardens, including Ocimum urticifolium and Ruta chalepensis, the medicinal plant knowledge of which is in the public domain. Beliefs have reported to have some contributions to conservation of medicinal plants. It was reported that medicinal plants collected during ‘Chegino’ (that means Monday, Wednesday and Friday) are not used, and limitation of days for collecting medicinal plants reduces the effect of over-harvesting.