Diversity and Traditional Use Knowledge of Medicinal Plants among Communities in the South and South-Eastern Zones of the Tigray Region, Ethiopia

: In the present study, the diversity of medicinal plants (MPs) and associated traditional knowledge of rural community herbalists to treat human and animals’ diseases were assessed in two districts in the Tigray Region, Ethiopia. Study participants were randomly selected for survey and focus group discussions, while key informant traditional healers were identiﬁed through snowball/chain-referral sampling. The informant consensus factor (FIC) by ailment category and ﬁdelity level (FL) for some MPs were determined. About 97 MP species were identiﬁed. Leaves, roots, and seeds are the parts predominantly used for phytomedication preparation to treat 30 human and 5 animal diseases. Diseases, such as epilepsy, arthritis, otitis media, and fever, are treated with a combination of 2–4 MPs. The FIC value ranged from 0.29–1.00, with most human diseases showing an FIC value of above 0.7. The FL value for the MPs ranged from 53–100%, with plants used to treat more than one disease tending to have lower FL values. Higher values of FIC and FL indicate high levels of traditional knowledge used to identify and administer medicinal preparations. Despite the frequent use of MPs, the four-cell analysis showed that most of them risk extinction due anthropogenic and climate factors. We recommend botanical gardens as a solution to sustainable conservation, study, education and a source for these declining MP species.


Introduction
The Earth's plant genetic resources offer diverse services to humans and the environment. To date, just a small segment of this vast plant diversity-in particular, crops of economic importance-have been extensively studied, while studies on the vast majority of medicinal plants are lacking. Medicinal plants (MPs) play a significant role in healthcare, either as traditional remedies or in the development of modern medicines. The people of Ethiopia have traditionally used MPs to treat various human and animal diseases [1][2][3] and many rural populations today still depend on traditional medicine. The dependency on traditional medicine could be due to the high cost of modern drugs, the inaccessibility to modern health institutions and cultural acceptability of the system [4][5][6].
The importance of herbal medicine in Ethiopian healthcare has attracted the attention of ethnobotanists, to better understand the diversity, use, ecology and traditional knowledge associated with herbal/phytomedicine [7]. Medicinal plants are defined as botanicals that provide people and animals with medicine to prevent disease, maintain health or cure ailments [8]. World Health Organization (WHO) expert groups define traditional medicine as the sum of all knowledge and practices, whether explicable or not, used in the diagnosis,

Geo-Physiological Features of the Study Areas
Our study was conducted in nine villages in the Degua Tembien and Alajie districts of the Tigray Region (Table S1 and Table S1). The sampled landscape covers hills, plains and valleys, to ensure the representativeness of the study sites.

Land Use and Climate of the Study Areas
The study sites are predominantly crop-livestock farming systems and under pressure from high human population density. Land is primarily used for cereal-dominated crop production to the extent that lands unsuitable for crop production are included under this land-use category. The amount of land under natural forests, vegetation, bushes, trees and grasslands has been dramatically declining in both districts, whereas agricultural lands are expanding in response to increasing demands for food production [16]. These changes (in land-use and land-cover systems) have a great impact on the areas' agrobiodiversity and, consequently, on the sustainability of agricultural production and productivity [17]. The districts are characterized by their bi-modal rainfall pattern, where the short (Belg) rains occur from March to April and the long (Meher) rains between June and September. The Degua Tembien district is characterized by relatively cool climatic conditions, with a mean annual rainfall of 778 mm and an average annual temperature of 15.1 • C [18,19]. Similarly, the Alajie district is characterized by cool-to-warm climatic conditions, with a mean annual rainfall of 980 mm and a mean annual temperature of 15.7 • C. The remaining months are characterized by a dry summer climate, which exposes the vegetation to long periods of drought. The soil samples were collected using an auger soil sampler and analyzed at the Mekelle University soil physics laboratory, which confirmed that the analyzed soil samples are clay loam.

Land Use and Climate of the Study Areas
The study sites are predominantly crop-livestock farming systems and under pressure from high human population density. Land is primarily used for cereal-dominated crop production to the extent that lands unsuitable for crop production are included under this land-use category. The amount of land under natural forests, vegetation, bushes, trees and grasslands has been dramatically declining in both districts, whereas agricultural lands are expanding in response to increasing demands for food production [16]. These changes (in land-use and land-cover systems) have a great impact on the areas' agrobiodiversity and, consequently, on the sustainability of agricultural production and productivity [17]. The districts are characterized by their bi-modal rainfall pattern, where the short (Belg) rains occur from March to April and the long (Meher) rains between June and September. The Degua Tembien district is characterized by relatively cool climatic conditions, with a mean annual rainfall of 778 mm and an average annual temperature of 15.1 °C [18,19]. Similarly, the Alajie district is characterized by cool-to-warm climatic conditions, with a mean annual rainfall of 980 mm and a mean annual temperature of 15.7 °C. The remaining months are characterized by a dry summer climate, which exposes the vegetation to long periods of drought. The soil samples were collected using an auger soil sampler and analyzed at the Mekelle University soil physics laboratory, which confirmed that the analyzed soil samples are clay loam.

Study Participant Selection and Data Collection
A total of 135 farmers (47.4% women) participated in this study. A total of 3 villages were studied in the Degua Tembien and 6 in the Alajie districts; 15 farmers were selected from each village (Table S1). Some of the key informant traditional healers, a sub-sample of the participants from each district, were sampled through the snowball/chain-referral sampling method, while the remaining participants were randomly sampled. We conducted transect walks to collect samples of plant diversity, which were brought to one place for characterization, where participant farmers were asked to sort the plant specimens into various categories based on their use. The specimens were classified as cultivated crops, wild edible plants, wild non-edible and medicinal plants. The research team

Study Participant Selection and Data Collection
A total of 135 farmers (47.4% women) participated in this study. A total of 3 villages were studied in the Degua Tembien and 6 in the Alajie districts; 15 farmers were selected from each village (Table S1). Some of the key informant traditional healers, a sub-sample of the participants from each district, were sampled through the snowball/chain-referral sampling method, while the remaining participants were randomly sampled. We conducted transect walks to collect samples of plant diversity, which were brought to one place for characterization, where participant farmers were asked to sort the plant specimens into various categories based on their use. The specimens were classified as cultivated crops, wild edible plants, wild non-edible and medicinal plants. The research team subsequently filtered out the MPs and went back to the same community to further research the MPs for traits presented in Tables 1 and 2. Data were collected through participatory focus group discussions (FGDs), followed by key informant interviews (KIIs) with eight selected traditional healers to acquire information that cannot be disclosed to the wider community. The traditional healers in each district were selected using the exponential non-discriminative snowball sampling or chain-referral method after the survey, whereby each traditional healer referred others to be included in the study. The traditional healers were considered to have good knowledge of medicinal plants due to their dependency on traditional medicine. Crush young leaves and tie on to the affected part. ** Parts of two or more plants are combined and used to treat fever. ⸸ Intestinal parasites include tapeworm and hookworm, ⸶ information obtained from key informant; δ snake and other insect repellents. Crush leaves, blended with butter and applied to the head; dried parts are put on the fire and the smoke is inhaled.

Herbs Seeds Oral
Grind the seeds, mix with water and drink.

Shrub Roots Inhalation
Mix the root with Hangoro midri, boil and inhale the vapor.

Shrubs Fluid Topical
Apply extracted fluid to the affected area.
Herbs/shrubs Bulbs/seeds Topical Blend plant part with unguents/butter and apply to the inflamed area.

Shrub Leaves
Apply prepared plant remedy to the affected areas.

Herbs Seeds/leaves Topical
Boil in water and wash with it; or leaves burned to ash, blended with butter and applied to affected parts.
Herbs/shrubs Leaves/stems/seedsInhalation Boil plant parts, sometimes together, and inhale every evening until cured.

Trees/shrubs Roots/leaves Oral
Chew the parts, swallow the juice, but spit out the residue.

Shrubs/herbs Leaves/roots Fumigation
Burn the roots and leaves and fumigate the house to repel insects.

Tree Leaves Topical
Crush young leaves and tie on to the affected part. * Parts of two or more plants are combined and used to treat fever. ⸸ Intestinal parasites include peworm and hookworm, ⸶ information obtained from key informant; δ snake and other insect epellents.   Crush young leaves and tie affected part. ** Parts of two or more plants are combined and used to treat fever. ⸸ Intestinal parasit tapeworm and hookworm, ⸶ information obtained from key informant; δ snake and oth repellents. Crush young leaves and tie affected part. ** Parts of two or more plants are combined and used to treat fever. ⸸ Intestinal parasit tapeworm and hookworm, ⸶ information obtained from key informant; δ snake and oth repellents.

Ethnobotanical Data Collection
The ethnobotanical surveys were carried out using a semi-structured questionnaire and KIIs in the local Tigrigna language. Participants' informed consent to document and disseminate their local knowledge was obtained before the administration of the survey through conversations with local enumerators who explained the objectives of the study. After consent was provided in each district, we undertook a transect walk, covering approximately 3 km 2 to collect the medicinal plants analyzed. Several transect walks were carried out in each village, in various directions, to sample the representative plants for the study. Researchers from Mekelle University and development agents from each district who spoke the local language facilitated the transect walks and sample collection processes.
To further study the part or parts of the identified MPs used for medicinal purposes, their method of preparation and administration, 45 farmers were re-sampled from the 135 participant farmers for a second round of FGDs (Table 1, Table 2 and Table S1). Key informant traditional healers in each district were interviewed to obtain their traditional knowledge. The FGDs and key informant interview data on the ailments/illnesses treated by MPs were collected, and we identified 30 (for human) and 5 (for animals) ailments/disease types, respectively (Tables 1 and 2).

Data Analysis
Descriptive statistics, such as the percentage and frequency, were employed to summarize the ethnobotanical data. The factor of informant consensus (FIC) was calculated for categories of human/livestock ailments to identify informants' agreement on the reported cures following the approaches used by other scholars [20,21]. FIC was calculated as follows: the number of use citations for aliment categories (n ur ) minus the number of species used (n t ) for that aliment, divided by the number of use citations for each aliment, minus one.
The fidelity level (FL)-the percentage of informants claiming to use a certain plant species for the same major purpose-was calculated for the most frequently reported ailments, as described by Alexiades [22]: where N p is the number of informants that claim the use of a plant species to treat a particular disease and N is the number of informants that use the plants as a medicine to treat any given disease. The average amount of variability in the analyzed variables was presented as the standard deviation (SD), calculated for the sampled MPs from the target areas. The distribution pattern of the MPs was analyzed using four-cell analysis (FCA). The participants were asked to place the collected samples of each medicinal plant species into one of the four quadrants of the FCA, and the total number of species in each quadrant was counted. According to the standard definition of FCA [23], species' allotment into the different quadrants using a participatory methodology indicates both the abundance and distribution pattern, including different levels of conservation concern.

Diversity of MPs Identified in the Study Areas
Despite the study covering only a small portion of the Tigray Region, 97 medicinal plants pertaining to over 90 species were identified by local communities in the Degua Tembien and Alajie districts (Tables 1, 2  herbs were the most abundantly used for the treatment of human and animal diseases within these communities, closely followed by shrubs and, to a much lesser extent, trees.
herbs were the most abundantly used for the treatment of human and animal diseases within these communities, closely followed by shrubs and, to a much lesser extent, trees.
According to the FGD participants, fresh plant specimens are most-commonly used by traditional healers in herbal medicine preparation. Plant parts include leaves, roots, seeds, latex (fluids), stems, bulbs, bark, clades, and flowers (Figure 2A). Most of the herbal remedies were prepared from leaves (51%) and, to a lesser extent, the roots (18%) and seeds (17%), compared to other parts, such as the stem, bark, milk, clades, flowers, and latex ( Figure 2B).

Diseases Treated Using Herbal Medicine
The local communities of the Degua Tembien and Alajie districts use MPs to treat about 30 human and 5 animal diseases, and to repel insects (Tables 1 and 2). The number of MPs identified to treat a single disease ranged from 19 (wound/swelling) to 1 (external bleeding) for humans, and 9 (for blood sucking insects) to 2 (rabies) for animals. The types According to the FGD participants, fresh plant specimens are most-commonly used by traditional healers in herbal medicine preparation. Plant parts include leaves, roots, seeds, latex (fluids), stems, bulbs, bark, clades, and flowers ( Figure 2A). Most of the herbal remedies were prepared from leaves (51%) and, to a lesser extent, the roots (18%) and seeds (17%), compared to other parts, such as the stem, bark, milk, clades, flowers, and latex ( Figure 2B).

Diseases Treated Using Herbal Medicine
The local communities of the Degua Tembien and Alajie districts use MPs to treat about 30 human and 5 animal diseases, and to repel insects (Tables 1 and 2). The number of MPs identified to treat a single disease ranged from 19 (wound/swelling) to 1 (external bleeding) for humans, and 9 (for blood sucking insects) to 2 (rabies) for animals. The types of human diseases reported to be treated by these various medicines include wounds/swelling, abdominal pain, eye infection, toothache, hepatitis, cough, tonsilitis, bone fractures, mental illness/epilepsy, fever, skin infections, ear infections, hair follicle infection, herpes simplex virus, intestinal parasites, hemorrhoids, and herpes zoster (Table 2). Similarly, locally sourced MPs are used to treat animal diseases, such as rabies, wounds, abdominal pain, and eye infections, and to rid them of infestation from blood-sucking insects ( Table 2).
The largest diversity of medicinal plants (19) is used to treat wounds/swellings, which is presumably associated with injuries linked to the rural communities' means of living. The probability of obtaining a topical abrasion or injury while operating on farms, collecting and gathering foods, medicinal plants and/or firewood, and the common practice among rural communities of traveling barefoot from place to place, might justify why so many of the herbal plants identified are used to treat wounds and swellings.

Local Knowledge of Traditional Medicine
In Ethiopia, rural communities' lifestyle, coupled with poor accessibility to and affordability of modern medicine, drives the demand for natural remedies to treat both human and animal diseases. Our study confirmed that both communities in Degua Tembien and Alajie are endowed with traditional knowledge about MPs, the parts to be used to treat diseases, as well as methods of herbal medicine preparation, administration, and application frequency (Tables 1, 2 and S2). The FIC values calculated ranged from 0.29 to 1.00, with most of the diseases having an FIC value greater than 0.7 (Table 3). We report higher FIC values for many of the diseases, which might indicate the higher incidence of these diseases within the community. However, diseases treated by herbal medicines, but only known to traditional healers, had lower FIC values. Diseases, such as wounds/swelling, eye infection, tonsilitis, ear infection, constipation, gonorrhea, and joint inflammation, have a relatively higher FIC value, which might indicate the higher incidence of these diseases in the two districts. Disease types that are treated by traditional healers The FL values for all MPs ranged between 53 and 100% (Table 4). Similarly, MPs that are frequently used by the local community have higher FL values than those that are less popular; but MPs only known to traditional healers to treat single diseases usually have an FL value of 100% (Table 4). For instance, Brassica nigra L. and Ruta chalepensis L.-plants grown by most households as home-garden vegetables for food, and that are also used to treat coughs, malaria, and fever, among other ailments-have an FL value of 100%, while MPs known to few traditional healers, such as Rumex nervosus, Merendra bengalensis and Artemisia abyssinica, have <70% FL values (Table 4). Similarly, MPs used to treat diseases, such as the herpes simplex virus, evil eye, gonorrhea, stabbing chest pain, and external bleeding, are known to few community members and hence have a lower FL.

Herbal Medicine Preparation, Form, and Dosage
Different plant parts are used to prepare herbal medicines ( Figure 2) through drying, chopping, maceration, boiling, direct compression of the fresh leaves against ailing parts, and squeezing the liquid contents. Detailed methods of the preparation, administration and doses are presented in Table 1, Table 2, and Table S2. The key informant traditional healers may combine two or more MPs to treat certain diseases, such as epilepsy, fever, arthritis, otitis media, herpes simplex virus, and bone fractures (Table S2).
The most common administration methods for the herbal medicines are summarized in Figure 3, which are oral (43%), topical (38%), inhalation (13%), nasal (4%) and ocular (2%). The dose and frequency of the administration are also determined by the number or size of the leaves, stems, roots, seeds, or fruits prepared. Most of the herbal medicines are administered once daily for a few days (ranging from a day to seven days). There are cases in which the medicines are administered for months, until the ailment is cured. The informants indicated that, when herbal medicines are administered for the first time, the initial doses are small and are gradually increased and adjusted as a result of observing the patient's condition and symptoms. When new herbal medicines are tried for the first time, milk or whey is prepared and set aside, ready to be given to the patient, in case signs of toxicity are observed. We also learned from the participants in Degua Tembien that whey is administered to women after childbirth to ensure rapid uterus recovery and to improve their libido. formants indicated that, when herbal medicines are administered for the first time, the initial doses are small and are gradually increased and adjusted as a result of observing the patient's condition and symptoms. When new herbal medicines are tried for the first time, milk or whey is prepared and set aside, ready to be given to the patient, in case signs of toxicity are observed. We also learned from the participants in Degua Tembien that whey is administered to women after childbirth to ensure rapid uterus recovery and to improve their libido.

Abundance of the Identified Medicinal Plants
The MPs sampled during the transect walk and those brought by participant farmers were analyzed for their abundance using FCA (Figure 4). Most of the sampled MPs can be classified as rare. MPs, such as Rhamnus prinoides (gesho), Ruta chalepensis L. (Tena Adam) and Brassica nigra L. (Senafich), are cultivated as backyard crops on small areas of land by many farmers, and are hence not under threat of extinction. The participants indicated that samples of the studied MPs were mostly collected from gorges, valleys, mountains, under hedgerows, roadsides, patchy woodlands, church compounds, and homestead backyards, implying that MPs grow mainly in inaccessible places, other than on cultivated land. These resources are under the threat of extinction due to anthropogenic and natural factors. The participant farmers claimed that the associated indigenous knowledge is also threatened because of reduced interest from the younger generations to learn about the MPs and their use for medicinal purposes. The anthropogenic factors threatening the survival of MPs include the expansion of agricultural lands, and the overgrazing and overharvesting of the plants by traditional healers. Drought has been mentioned as the major Percentage reported

Abundance of the Identified Medicinal Plants
The MPs sampled during the transect walk and those brought by participant farmers were analyzed for their abundance using FCA (Figure 4). Most of the sampled MPs can be classified as rare. MPs, such as Rhamnus prinoides (gesho), Ruta chalepensis L. (Tena Adam) and Brassica nigra L. (Senafich), are cultivated as backyard crops on small areas of land by many farmers, and are hence not under threat of extinction. The participants indicated that samples of the studied MPs were mostly collected from gorges, valleys, mountains, under hedgerows, roadsides, patchy woodlands, church compounds, and homestead backyards, implying that MPs grow mainly in inaccessible places, other than on cultivated land. These resources are under the threat of extinction due to anthropogenic and natural factors. The participant farmers claimed that the associated indigenous knowledge is also threatened because of reduced interest from the younger generations to learn about the MPs and their use for medicinal purposes. The anthropogenic factors threatening the survival of MPs include the expansion of agricultural lands, and the overgrazing and overharvesting of the plants by traditional healers. Drought has been mentioned as the major climatic factor reducing MP diversity in both areas. Some key informants indicated that many medicinal plants they had once collected in their area have been lost, forcing them to travel long distances-even to other districts, such as Axum-in search of these specific plants. climatic factor reducing MP diversity in both areas. Some key informants indicated that many medicinal plants they had once collected in their area have been lost, forcing them to travel long distances-even to other districts, such as Axum-in search of these specific plants.

Discussion
This study identified 97 MPs in the Degua Tembien and Alajie communities of Ethiopia. This implies that there is a wealth of biological resources available for community health care in areas where physical accessibility and economic affordability of modern medicine is lacking, thus continuing the demand for natural medicines. Most of the MPs identified are herbs followed by shrubs, and the most harvested parts used in the preparation of traditional herbal medicines include the leaves, roots, seeds, stems, and fruits. These preparations can be administered in various forms and in different doses and frequencies to cure approximately 30 human and 5 animal diseases, in addition to controlling pest and insect infestations ( Table 2).
This data aligns with those collected by many other scholars on the dominance of herbs and shrubs as selected MPs by traditional healers, who mainly harvest the leaves, roots, and seeds [24][25][26]. The practice of using traditional medicine, identifying the plants, their specific parts, and the tendency to use similar groups of plants, mainly herbs and shrubs, throughout Ethiopia suggests that the transfer of this traditional knowledge may have originated or have been spread through common venues, such as churches, which have had a profound and extensive impact in the country. In particular, the knowledge of traditional medicine in the Ethiopian Orthodox church dates back to the 15th century AD, even though the Metsehafe Fews (book of remedy) text of first traditional remedies was published around the mid-17th century in the Ge'ez language [7,27].
Herbal medicines are administered in various forms (Figure 3), with oral and topical administration being the most extensive. Again, the literature cites other studies conducted in various parts of Ethiopia and elsewhere in the world [11,12,27], where the same methods of administration were also reported. Even though not well captured in the literature, some herbal medicines are also administrated through the ear. Herbal remedy preparations are usually taken with water, milk, coffee, honey and bread, or injera at varying doses, depending on the age of the patient and the type of the disease. Lower doses are usually administered to children, lactating and pregnant mothers, and seriously ill persons.
About 30 types of humans and 5 animal diseases and pest infestations are treated with herbal medicines, which are prepared from a diversity of plant species in the two communities (Tables 1 and 2). For instance, 19 and 15 plant species were known by the communities to treat wound and abdominal pains, respectively. On the other hand, single plant species are known to treat some disease types, such as the evil eye, gonorrhea, tuberculosis, heart disease, and external bleeding (Table 1). Some plants are also used to treat diseases, such as the herpes simplex virus, herpes zoster (Almaz belechira), and epilepsy, for which modern medicines are not widely available in the rural areas of Ethiopia. This data reflects similar findings reported by studies conducted in other parts of Ethiopia [4,16,20,28]. In some cases, MPs are prepared in combinations. For instance, a combination of Ocimum lamifolium and Ruta chalepensis parts are prepared to treat fever. Similarly, three plant species (Olea europea + Eucalyptus globulus + Schinus mole) are combined in preparations that also treat fever, which presumably indicate the wealth of traditional knowledge of MPs. The human herpes simplex virus is treated with extracts prepared from a combination of four medicinal plant species (Rumex nervosus + Lepidium sativum + Citrus aurantifolia + Plumbago zeylanica). The combined use of two or more medicinal plant species to treat human and animal diseases was also reported in different parts of Ethiopia [20,29]. These combination medicines are prepared from MPs that contain a range of pharmacologically active compounds that could make it difficult to know which plant or specific part contributed the ingredients that produce the therapeutic effect [30]. Overall, the FIC value ranged from 0.29 (for human simplex virus) to 1.00 (for heart disease) ( Table 3). Diseases treated with single MP preparations tend to have higher FIC values. The magnitude of the FIC and FL is likely to vary between localities and studies.
For instance, Mengistu et al. [21] reported a higher FIC value for abdominal pain than that reported in our study. On the other hand, Teklehaymnot and Giday [20] reported a lower FIC value for "evil eye" than our study, but comparable FL values for common MPs. The knowledge about MPs' FIC and FL values is helpful in distinguishing MP species known to the wider community and those only known to a few traditional healers. This knowledge is important in the design of further MP studies, and conservation and production strategies.
The 98 MPs identified, pertaining to more than 90 species, from which are derived a broad diversity of herbal medicines, the diverse dosage of prescription, and forms of administration indicate that the two communities have a wealth of traditional knowledge in regard to traditional medicine. This is presumably because MPs make up the main source of health remedies and natural medicines used to treat the majority of people in rural Ethiopia. Traditional healers provide these cures at a much lower cost to rural communities than modern medicine [31,32]. However, traditional healers' indigenous knowledge cannot be fully captured and documented in ethnobotanical studies, as the procedures of herbal medicine preparation and administration remain a guarded secret. This is partly because herbal medicine is the foundation of their livelihood and is therefore considered as a business strategy; secondly, many traditional healers believe the more their knowledge is shared, the less effective and powerful their medicines become [11,12,27]. They would not disclose certain aspects of their practice, even to researchers for scientific purposes. The importance of MPs as a source of income for traditional healers and cheap medicine for the community justifies the need for their conservation through sustainable utilization. However, the fact that they are not cultivated or that they grow in remote locations or are being over-harvested may not make this possible, unless collected and grown in botanical gardens.
The scarcity of the species samples collected during the transect walk sounds the alarm for the dwindling species abundance in both study areas (Figure 4). This scarcity could be largely associated with the destruction of natural habitats from the expansion of farmlands, under pressure from continued population growth and the need for crop cultivation. Such human-driven factors were reported as major causes of the loss of many thousands of hectares of forest, harboring medicinal plants, every year over several years in Ethiopia [10,33,34].
To protect these valuable plant species and preserve the associated indigenous knowledge of herbal medicine, organized conservation and cultivation centers need to be established. The establishment of botanical gardens for medicinal plants could be suggested for both the studied sites for multiple purposes. Botanical gardens would play a key role in the conservation, production, and utilization of the already threatened MP species. In addition to conservation, they would create opportunities for research activities related to their ecology, taxonomy, breeding, biotechnology and pharmacology, and could serve as education centers for students and the public. We posit that the establishment of botanical gardens would:

1.
Increase the interest of the young generations in the use of herbal medicine for health maintenance and treatment.

2.
Promote herbal medicine as a livelihood strategy for many individuals.

3.
Continue to provide traditional healers with access to traditional MPs within their vicinity, so that they are not forced to travel long distances to gather them.
Furthermore, the sustainable production, use, and conservation of these plants would be ensured. The botanical gardens will be of increasing importance to conserve existing biodiversity by reducing the effects of anthropogenic and climate change on these important biological resources.

Conclusions
The diversity of MPs in Degua Tembien and Alajie is high, compared to the diversity presented in other studies in other parts of Tigray. The communities treat a broad range of common and important human and animal diseases with these natural resources. The indigenous knowledge of processing and administering herbal medicines is quite rich.
Despite these facts, MPs are mostly located along roadsides, in valleys, at the foothills of mountains, in patchy woodlands and in churchyards, mostly because of the expansion of agricultural land, deforestation and climate change. Furthermore, the unplanned and unsustainable practices of traditional healers, for example, uprooting MPs for harvesting root parts, could mainly be attributed to the decrease in or loss of these plants. Therefore, interventions that closely engage and inform herbal medicine harvesters are important to halt and reverse the negative impact they impose on these natural resources. One such intervention strategy could be the establishment of botanical gardens at both study sites. These would support the conservation of these valuable genetic resources, serve as an open space for research, act as education hubs to promote a wider appreciation for their use among younger generations, and enable traditional healers to access sustainably harvested MPs in a single place.
Supplementary Materials: The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/d14040306/s1, Table S1: Geophysical location and cropping system of the study locations within each district, and Table S2: Medicinal plants used to treat diseases (both human and animal) in the Degua Tembien and Alajie districts, Tigray.