Discussion and conclusions
Results showed that Ankober District is rich in medicinal plant diversity as shown by the presence of 135 species exhibiting wide taxonomic diversity (125 angiosperm, two gymnosperm and one fern genera in 68 angiosperm, two gymnosperm and one fern families). The diversity has also been made obvious in the elaborate system of traditional naming of plants (based on morphology of a plant part or its remedial uses) and the indigenous knowledge engraved in each medicinal plant species name and knowledge about the uses of each medicinal plant species. Results have also proved the role played by traditional medicinal plants and the local community holding considerable traditional health knowledge in assisting the primary healthcare needs of the District. The number of medicinal plants harvested in the District is found to be far higher than that of other areas in the country investigated for their ethnomedicinal wealth [
24,
25,
34,
53‐
55]. Although cultural, economic, ease of accessibility and efficacy related factors might have played major roles for the people of Ankober to rely on traditional medicine, the cultural factor might have been the most important one resulting in a sentimental adherence to the ancestral medical traditions/practices by upholding it as a highly valued heritage of the society or of the great fathers and mothers.
Dominance of medicinal plant species from families Asteraceae, Fabaceae, Solanaceae, Lamiaceae, Cucurbitaceae, Ranunculaceae and Rosaceae could be attributed to their wider distribution and abundance in the flora area [
28,
48,
54]. This is also confirmed by consistent recording of ethnomedicinal uses of species from the aforementioned families in different Ethiopian ethnobotanical inventories [
25,
26,
30,
33,
53]. Moreover, the wide utilization of species from these families might relate to the presence of effective bioactive ingredients against ailments [
56].
Most medicinal plants used in the area (38%) were found to be herbs. This could relate to the fact that they are easily accessible in the nearby areas than trees and shrubs often harvested from patches of forests distantly located from resident areas. The finding agrees with the general pattern of dominance of herbaceous species seen in most medicinal plant inventories in Ethiopia and other countries [
25,
33,
57‐
59]. Wild habitats of Ankober were found to be major pools of traditional medicinal plants providing about 74% of all reported medicinal plants. However, the investigation showed that these habitats are subjected to anthropogenic influences and consequently shrinking in size due to an ever-increasing population pressure resulting in the loss of many medicinal species sheltering in the wild. Our observation is also in agreement with previous reports of overdependence on wild habitats to harvest medicinal plants [
26,
34,
35] than an effort to cultivate and use them sustainably.
Overexploitation of entire root parts for majority of medicinal plant preparations (44%) shows the threat posed on long-term survival of corresponding medicinal plants. Mining of root parts of medicinal plants was also commonly reported by other ethnomedicinal inventories elsewhere [
8,
26,
30,
33,
60,
61]. Harvesting of roots kills the parent plant and could be a severe threat for survival of the often rare and slowly reproducing medicinal plants of the area. As leaves of medicinal plant species were also reported to be harvested for most remedy preparations next to roots, gathering leaves could be promoted as a more sustainable method since in most cases at least a number of leaves are left over on the parent plant which then allows them to carry on its life functions.
Results also showed prominent use (69.9%) of freshly harvested plant parts for traditional remedy preparation used against various ailments. The recurrent use of freshly harvested medicinal plant materials in the area is reported to be related to the notion of attaining high efficacy using active ingredients of fresh plant parts which they thought could be lost on drying. Other ethnomedicinal inventories [
26,
33] have also indicated wide use of fresh plant materials for remedy preparations due to reportedly better efficacy related factors than using dried plant materials.
The significant difference (P < 0.05) on average number of medicinal plants reported by different age groups compared in this investigation showed that indigenous knowledge on use of medicinal plants is still strong with elderly people (4.90 ± 0.13 ) than in the younger generation (2.59 ± 0.08). Moreover, the observed extremely significant difference (p = 0.0001) showed the gap between generations and the decline of indigenous knowledge on medicinal plants down generations. This could be attributed to the impact of modernization (including urbanization and advent of formal education) and the very poor system of sharing indigenous knowledge (through word of mouth, with maximum secrecy and only along family lines) on medicinal plants to the younger generation. The scenario is the same for other cultural groups in Ethiopia [
24,
26,
30,
34] and elsewhere [
6,
31,
62]. The output calls for an effort to close the observed generation gap through continuous professional support and training of local communities with an objective of preserving their traditional health knowledge and practices through systematic documentation. Silva
et al.[
6] explained that greater knowledge of older people on medicinal plants is the result of high degree of opportunity for more cultural contact and experience with plants and associated therapeutic uses than that of younger people. Absence of continuous cultural interaction with plants was also reported as one factor for loss of traditional knowledge down generation [
2].
The other significant difference (p = 0.0001) observed between key and local; and literate and illiterate informants could relate to the impact of age-old experience and maximum degree of secrecy in using medicinal plants in the former, and modernization in the latter case. Similar results were reported by [
24,
30,
63]. According to [
64], community members who have greater contact with medicinal plants are more knowledgeable about therapeutic uses of the plants than those with intermittent contact.
Male informants of the District were found to report more medicinal plants on average (4.23 ± 0.13) than women (3.85 ± 0.19) even though the difference was not statistically significant (p = 0.1075). Thus, the result indicated that both men and women are knowledgeable on use of traditional plant remedies despite the relative dominance of medicinal plant tradition by men which could relate to the traditional flow of information along the male line in the country [
30] and elsewhere [
62,
65]. Occurrence of relatively equivalent medicinal plants knowledge among men and women traditional medicine practitioners was reported by [
4] for three communities in northeastern Brazil and by [
66] for a community in southwest Niger. In contrast, [
67] have reported the presence of more specialized knowledge on medicinal plants among women informants than men since they are often looked to diagnose and treat certain types of diseases. Generally, gender based differences in medicinal plant knowledge can be derived from experience and degree of cultural contact with curative plants [
64].
The number and different types of diseases (69 disease types) for which traditional healers were most visited by patients indicated a preference of local people in the study area to visit traditional healers and the nature pharmacy. Economic, cultural, efficacy and availability factors were reported as the key factors which lead the community to knock at the door of traditional healthcare practitioners than the few distantly located healthcare centres with unaffordable prices. Similar findings were reported by [
26,
27,
53].
Visual inspection of patients is the more obvious diagnostic method practiced by all local healers in the area. Although changes in body temperature, skin and eye colour, appetite and physical appearance help traditional healers to detect which patients face disorders it was only through visual experience that identification of diseases and prescriptions seem to be made. Other researchers [
11,
27,
29,
42,
46,
68] have also reported similar diagnostic methods in different cultural groups. Misidentification of diseases commonly leads to mis-prescription which may result in adverse effects to patients. Even though dosages of remedies for various ailments were reported to be determined based on age, occurrence of pregnancy, physical fitness/appearance and gender of the patient, there were no standardised measurements or guidelines set by traditional healers. Overdose of remedies was also reported to bring adverse effects like vomiting, diarrhoea, burning sensations and sometimes fainting of the patient. Lack of precision and standardization has been mentioned as a global drawback of the traditional healthcare system [
22]. Traditional healers in our study area reported the use of different antidotes including BESSO, milk, coffee, honey, yoghurt, and butter for reversing adverse effects and stabilising any disorder. The same pattern of using antidotes was also reported for other cultural groups elsewhere [
25,
26,
33].
The dominant use of medicinal plant decoctions for various ailments might be related to their proven effectiveness over many years of trial and indigenous knowledge accumulated on efficacy of such preparations. Decoction was also reported as one of the major ways of remedy preparation in ethnomedicinal inventory of other socio-cultural groups in the country [
27,
33].
The result from market survey of medicinal plants indicated that most medicinal plants (81%) have no marketability report and were not available on major market places of the District during the time of research. This would show that the majority of medicinal plants are collected from the wild for remedy preparations only when the need arises. Although 19% of the medicinal plants were available on the market
Echinops kebericho,
Embelia schimperi,
Hagenia abyssinica,
Withania somnifera and
Silene macrosolen were the only ones to be sold or purchased for their traditional medicinal uses. The market value of these species (with a price range from 0.21 USD per bunch of root or jug of inflorescences to 0.3 USD for a cup of fruits) showed the income generation potential of a number of medicinal plants and gives an indication of potential demand of those marketable plants by the community. However, such marketability could also indicate that the plants are under pressure since they are purposefully hunted for economic reasons. Other reportedly marketable medicinal plants of Ankober were mainly gathered and sold for their uses related to edibility, lumbering, firewood and construction purposes. Although the investigation indicated current market potential of medicinal plants in Ankober, a relatively wider domestic trade of Ethiopian medicinal plants was reported for other cultural groups in the country [
61,
68‐
70]. Thus, our finding can also be used as a base line for a future in-depth study of the money-making potential of medicinal plants of the area through successive market survey over number of years and value chain analysis study of potential plants.
The highest recorded ICF values (0.7 and 0.65) indicated best agreement among informants’ on the use of medicinal plant species reported to be used for treating gastro-intestinal, and parasitic and dermatological diseases, respectively. The observed highest informants’ agreement coupled with high plant use citations for these disease categories could also indicate the relatively high incidence of the latter diseases in the area. According to [
52], high ICF values are important to identify plants of particular interest in the search for bioactive compounds. Accordingly, about 21 medicinal plants of Ankober (with high ICF values) for treating gastro-intestinal and parasitic diseases are under investigation for their pharmacological properties by our research theme.
The reported highest fidelity level values for
Zehneria scabra (95%) and
Ocimum lamiifolium (93.33%) against febrile diseases; and
Hagenia abyssinica (93.75%) against gastro-intestinal and parasitic diseases could be considered as a clue for the high healing potential of these plants against the corresponding diseases. Plants with highest fidelity level values could also be targeted for further phytochemical investigation to prove the bioactive components that are responsible for their high healing potential [
52,
55]. Accordingly, further activity testing experiments are being carried out on extracts of these species by our research group.
The output of a direct matrix ranking exercise showed highest values/ranks for a number of multipurpose medicinal plants of the study area including
Podocarpus falcatus,
Olea europaea and
Ekebergia capensis. The result indicates that these plants are exploited more for their non-medicinal uses than for reported medicinal values. Overharvesting of multipurpose medicinal plant species for agricultural tool, construction, lumbering and firewood purposes were found the responsible factors aggravating depletion of the species in the area. Thus, the result calls for an urgent complementary conservation action to save the fast eroding multipurpose medicinal plant species of the area. Yineger
et al.[
33] has also reported the same pattern of highest exploitation of multipurpose medicinal plants for uses other than their traditional medicinal importance in south eastern Ethiopia.
The preference ranking exercise helped to identify the most-preferred medicinal plant species to treat atopic eczema. Accordingly,
Olea europaea subsp.
cuspidata,
Allium sativum and
Datura stramonium scored highest values and were found the most-preferred ones to treat the disease. Ethnobotanical investigation done elsewhere in Ethiopia [
34] also reported the use of
Olea europaea subsp.
cuspidata for treating eczema. Further investigation of these species for their bioactive components against atopic eczema may bring promising results.
Lack of interest in traditional medicines was observed among the youngest generation of Ankober due to factors related to ‘modernization’. Similar findings were reported for other cultural groups in Ethiopia [
24,
26,
71]. It was also found that traditional healers show maximum secrecy in handling medicinal plant knowledge. Moreover, they try not to leak the knowledge out of the family circle. These facts coupled with the absence of any written document on medicinal plants of the area show the threat on the future use of ethnomedicinal potential of Ankober.
Generally, although Ankober District was found to be rich in medicinal plant diversity, the effort to conserve the plants and associated indigenous knowledge was observed to be very poor. The effort from some traditional practitioners to cultivate medicinal plants at home gardens calls for a sustained governmental support to promote overall in situ and ex situ conservation strategies for medicinal plants of the District. It is also recommended to establish a traditional healers’ association in the District and strengthen members by providing professional support and land to establish as much medicinal plant nurseries as possible so as to conserve the fast-eroding medicinal plant wealth of the area.