Introduction

From 1515 to 2331, useful medicinal and aromatic plants have been cataloged in Nepal [1,2,3,4]. These plants are frequently valued in rural areas for food, medicine, construction, fodder, and firewood. Rural livelihood is intrigued by folklore uses for the primary healthcare system [5]. The use of ethnomedicine in rural areas has been transmitted orally from one generation to the next [6], yet it has been threatened by sociocultural transformation [7], human migration, and the limited transfer and extension of ethnomedicinal knowledge [3]. Moreover, traditional and ethnomedical knowledge are sparingly documented [8]. Geography, ethnicity, age, occupation, education, and culture substantially impact traditional ethnomedical knowledge [9]. Assessment of the interaction between the variables of geography, socio-culture, and livelihood provides ample opportunity to conserve medicinal plant species and their associated knowledge [10]. Therefore, ethnomedicinal research is required to grow and maintain medicinal plants and their associated knowledge [11, 12].

Nepal is comprised of five disparate eco-physiographical regions: the Himalayas (23% of the total area and above 5000 m asl), the High Mountains (20%, between 3000 and 5000 m asl), the Middle Mountains (30%, between 1000 and 3000 m asl), the Siwalik Hills (12.8%, between 500 and 1000 m asl), and the flat, lowlands of Tarai (13.7%, < 500 m asl) [13]. The mid-hills and mountains are home to the greatest number of medicinal plants in Nepal and are associated with diverse ethnic groups [10]. Okhaldhunga is a hilly district with fragile socioeconomic conditions, limited access to health care, social stigma, and poor resource management [14]. It is one of the understudied districts, with few ethnomedicinal publications and records of the least-used medicinal plants [10, 15].

There is no any detail investigation and documentation of medicinal in Okhaldhunga as well as in Champadevi community; therefore, this study was carried out to document and catalogue the medicinal plant used by local people of Champadevi rural municipality, to analyze the distribution of use knowledge within the socioeconomic variables such as age, gender, ethnicity, education, religion, and occupation and to assess the challenges and threats constraining the population, use, and distribution of useful plants and their associated ethnomedicinal knowledge. We hypothesized that the use of medicinal plants in Champadevi rural municipality is related to socioeconomic variables (age, gender, ethnicity, education, religion, and occupation). This information on medicinal plant species is crucial for the conservation policy and implementation. Further, to promote traditional knowledge of Champadevi community people, help to promote their identity and help in medicine development.

Methodology

Study area

Okhaldhunga district has 53.34% ethnic (Janajati) people followed by Chhetri21.22%, Brahmin 9.19%), Dalit (15.38%), and others (0.87%) [16]. Champadevi rural municipality is one of the southwest rural municipalities of this district bordering south to Sindhuli and west to Ramechhap district, Koshi Province, eastern Nepal. The municipality's population was 16,528 as of the 2021 Census [16]. The municipality is divided into ten wards. For this study, we selected four wards (6, 7, 8, and 9) with 1399 households where we found several traditional healers (Fig. 1).

Fig. 1
figure 1

Map of the study area (Champadevi rural municipality with ward numbers 6, 7, 8, and 9)

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Bhramin, Chettri, Dalit, and ethnic (Janajati) are the major ethnicity of the area. The ward numbers 6 and 7 are dominated by Chhettri, 8 has equal domination of both Chhetriand Janajati, and 9 is dominated by Janajati. People were following Hinduism and Buddhism. However, the dominated one is Hinduism. Most of the people are indigenous people of this area. The out migration rate is highest in ward numbers 8 and 9.

Champadevi village consists of mixed vegetation types. The land use of the area comprises human settlement and built-up areas (9.93%), forested areas (55.32%), barren land (5.67%), agricultural land (7.52%), water bodies (4.54%), and lower vegetation or shrubs (17.02%). Agriculture and livestock husbandry are the primary livelihood options. The primary energy source for cooking, heating, fodder, and firewood collection is nearby forests. The area is rich in traditional knowledge, and elders rural residents collect forest products and treat ailments using traditional methods. The health facility in the area is limited; people access district headquarters (Siddhicharan municipality) to treat health disorders.

Methods

Data collection

We adhered to the International Society of Ethnobiology's code of conduct [17]. Each respondent's verbal consent was obtained prior to the survey. The field visit occurred between July and November of 2021.

We obtained 210 or more than 210 households out of a total of 1399 households of Champadevi rural municipality ward numbers 6, 7, 8, and 9 to be surveyed following the online platform (https://www.calculator.net/sample-size-calculator.html), keeping confidence level 95% with margin of error ± 5% and household proportion 20%. Therefore, we interviewed 224 respondents from different households of Champadevi rural municipality ward numbers 6, 7, 8, and 9 following stratified random sampling methods.The socioeconomic and demographic conditions of respondents along with the use and conservation of local medicinal plants were recorded. Three focused group discussions (eight to twelve respondents in each group) and interviews with seven key informants (four Dhami/Jhakri traditional healers and three Vaidhyas) were conducted to validate the information obtained from the discussions, interviews and informal meetings. There were several informal meetings held during evenings and mornings while staying and having tea in the tea-vendor houses. The selection of key informants was based on the references made by the respondents and village secretaries. A free list of valuable medicinal plants was compiled, validated, and verified using consensus of at least three local medicinal plant experts (Dhami/Jhakri traditional healers and Vaidhyas).

Demographic profile of the respondents

Among the 224 respondents surveyed, 105 were male (46.88%) and 119 were female (53.12%). The respondent's ages ranged from 20 to 90 years old. More than half of the respondents, 150 (66.97%), were between 20 and 59, while the remaining 74 (33.03%) were older than 60. Most respondents were Hindu (202; 90.18%) and held basic knowledge of education (137; 61.17%). Table 1 shows that most respondents were Chhetri (157; 70%), followed by Bhramin (31; 13.83%). The family's primary source of income was agriculture (176; 78.57%).

Table 1 Demographic profile of the respondents
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Plant collection and identification

Following Jain's [18] methodology, we gathered the voucher specimens for the final list. Each specimen was assigned the collection, place name, latitude, longitude, and code. Further consultations with plant taxonomists were conducted to verify the nomenclature of collected plant species. The identified specimens were compared to their originals at the National Herbarium and Plant Laboratories (KATH), Godawari, Lalitpur, Nepal. The voucher specimens with collection codes were submitted to the National Herbarium and Plant Laboratories (KATH), Godawari, Lalitpur, Nepal.

Land use change analysis

The Champadevi rural municipality land use classification map was extracted from the Nepal map for land use using GIS. Landsat-7ETM of 1999, Landsat-7ETM of 2010, and Landsat-7ETM of 2020 satellite images were downloaded freely from the US Geological Survey's (USGS) Earth Explorer website (http://earthexplorer.usgs.gov). Using ArcGIS 10.4, land use change was analyzed for 1999, 2010, and 2020. Supervised classification with a maximum likelihood classifier (MLC) was used for image classification and the preparation of base maps for detecting change [19]. An accuracy assessment was done following [20].

Quantitative and statistical analyses

Suitable quantitative methods and approaches were used in indices such as frequency of citation (FC) and relative frequency of citation (RFC) to enhance the indicative value of the ethnomedicinal study. Similar methods were used in hilly communities in India [21], whose characteristics resemble those of our study area. According to Tardio and Pardo-de-Santayana [22], the frequency of citation (FC) and relative frequency of citation (RFC) were computed.

$${\text{RFC}} = {\text{FC}}/{\text{N}}$$

where FC, number of respondents who mentioned the use of species; N, Total number of respondents who participated in a survey.

Diseases and ailments were grouped into 13 categories based on the International Classification of Primary Care (ICPC) [23]. Using a similarity index, the ethnomedicinal plants in this study and previous studies were compared [24, 25]. We compared our findings to other researchers from eastern Nepal [26,27,28].

$${\text{Rahman's similarity index (RSI)}} = d/\left( {a + b + c - d} \right)$$

where a, number of unique species in area A; b, number of species unique in area B; c, Number of common species in A and B; d, number of common species used for similar ailments in A and B areas.

While a & b ≠ 0 and c & d ≥ 0.

The Rahman's similarity index is used to show the cultural similarities of indigenous knowledge among the communities based on plant use knowledge [25].

Since the data of medicinal plants recorded per respondents were count data, to test the hypothesis that use of medicinal plants in Champadevi rural municipality is determined by socioeconomic variables (age, gender, ethnicity, education, religion and occupation), we used a generalized linear model (GLM) with quasi-Poisson options due to the over dispersion of the Poisson model in R 3.4.4 [29].

Results

We documented 149 plant species representing 68 families and 130 genera. Most species belonged to the Leguminosae, Solanaceae, and Zingiberaceae families, with seven species each. Moreover, the most prevalent genus was Allium, with four species, followed by Citrus, with three. Fever (30) was treated with the most species, followed by diarrhea (28), stomachache (22), and the common cold (22). Malaria (1), eye allergy (1), nose bleeding (1), and hematuria (1) were treated the least (Table 2).

Table 2 Medicinal plant recorded with Family, scientific name, habit, parts, used, mode of use, FC and RFC
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Habit with the plant parts used in medicine

Most recorded species, 69 (46.3%), were herbs, followed by trees, 48 (32.21%), shrubs, 22 (14.77%), climbers, 9 (6.04%), and parasites, 1 (0.67%). Nearly all plant parts were used in ethnomedicine. However, the most frequently used plant parts were leaves in 74 (49.67%) of the species, followed by fruit 30 (20.13%), flower 19 (12.75%), seed 11 (7.38%), whole plant 11 (7.38%), bark 11 (7.38%), root 7 (4.69%), stem 6 (4.02%), rhizome 5 (3.35%), and bulb 4 (2.68%) (Fig. 2).

Fig. 2
figure 2

Habit-wise parts of the plant used to treat diseases (where Rs = root/rhizome/bulb, seed/fruit, Lt = leaves, trunk, Lb = Leaves, bark, Br = bark, root/rhizome/bulb, T = stem, F = flower, B = bark, Lf = leaves and flower, P = bark, root, stem, leaves/leaves, bark, stem/root, leaves, flower/leaves, root, stem/bark, leaves, stem, fruits/stem, leaves, fruits, R = root/rhizome/bulb, S = fruits/seed, Lr = leaves, root, Ls = leaves, seed/fruit, W = whole plants, L = leaves, Par = parasites, Cli = climber)

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Relative frequency of citation (RFC)

The relative frequency of medicinal plant citations ranged from 0.004 to 0.955, with Curcuma angustifolia (0.9554) having the highest frequency, followed by Zingiber officinale. (0.9063), Artemesia indica (0.902), Allium sativum (0.893) and Nyctanthes arbor-tristis (0.879) (Fig. 3).

Fig. 3
figure 3

Top ten ranked plant species reported by respondent where there are ten radar lines one radar represent 0.1 and goes up to 1. The black solid point is the RFC value of the species

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List of plants with diseases treated

The recorded 149 medicinal plants were used to treat 48 disorders and 13 disease categories. The greatest number of medicinal plants (119) was employed to treat digestive disorders (Table 3).

Table 3 List of plant species used for specific categories of disease and ailments
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The use of medicinal plants varies with the sociocultural variables

Age and occupation were the only variables among age, gender, education, occupation, ethnicity, and religion significantly associated with the number of plants reported (Table 4). Figure 4 demonstrates that older individuals mentioned more medicinal plants (p = 0.0001) than younger individuals. People in the agri-business sector reported significantly (p = 0.003) more medicinal plants than those in other occupations.

Table 4 Summary table of the generalized linear model (GLM) with quasi-Poisson showing knowledge about the number of medicinal plants among the respondents where sign * indicates significance
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Fig. 4
figure 4

Number of plants reported with the age of the respondents

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Status of medicinal plants and their traditional knowledge

The major challenges and threats in ethnomedicine were the migration of young people to urban areas, land use change in the village, and a decreasing use of forest products. Respondents reported a decrease in the population of some plants (21) as a threat to conservation caused by untrained and unprofessional collection. The sharing of ethnomedicinal knowledge was believed to decrease the effectiveness of medicine; therefore, all the traditional healers (Dhami and Jhakri) and three Vaidhya (Ayurvedic physicians) were not effortlessly passing their knowledge to the younger generation. Further, the hegemony of allopathic medicine is cited as a concern for limiting ethnomedicine. From observation, it was found that in the entire surveyed area, only one botanical to distribute medicinal plants and products; however, there were four health centers to sell allopathic medicine. Similarly, youth were found to have a diminished interest in ethnomedicine. For instance, we recorded an average of 20 species per respondent, with 20- to 29-year-olds reporting an average of 14 plant species.

Changes in land use patterns also represent a significant obstacle for using ethnomedicinal plants. Two (1.34%) of the 149 species recorded were purchased from a market, while the remaining 147 (98.65%) were collected from agricultural land, 76 (51%), forest, 49 (32.89%) and fallow/transition land, 22 (14.77%). The land use change analysis revealed a 56.67% decrease in shrubland area and a 32.05% decrease in agricultural land area (Table 5), limiting the availability of medicinal plants. Change in land use also prevailed the dissented medicinal plants picking sites and traditional harvesting calendars.

Table 5 Summary of LULC change in the period 1999–2020 in hectares
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Discussion

We recorded more ethnomedicinal plants than previous studies from eastern Nepal [27, 30,31,32]. In indigenous community-centered studies, [30] focused on the Lepcha community of Illam district, eastern Nepal, and recorded 35 species, while the Rai community-focused study in the Bhojpur district, eastern Nepal, recorded 35 species [32]. A study from Kavrepalanchok District, central Nepal, recorded 116 species [33]. A study from the Machhapuchchhre rural municipality of Kaski District, Nepal, recorded 105 species [23]. A study from far west Nepal recorded 135 species [34]. A study conducted in villages of central and western Nepal reported 192 medicinal plants [35]. This indicates that the Champadevi area is rich in medicinal plant knowledge, similar to other parts of Nepal, which might be related to the geographical uniqueness and remote area inhabiting indigenous people lacking medical resources [36].

Our research demonstrated a similarity index of 0.077 to Bhattarai and Khadka [26], 0.054 to Bhattarai [27], and 0.050 to Shrestha et al. [28]. Least similarity indices (0.07–0.05) indicate that more unique species have been recorded in Okhaldhunga district, revealing that people rely more on locally available medicinal plants to treat illness.

The differences in the use of species may be attributable to the people's socioeconomic status, including a link to national roads and health facilities, as well as awareness [23] and easy access. The differences in the use of species may be bonded to the people's socioeconomic status, including a link to national roads and health facilities, as well as awareness. It is evident that the people of remote and hilly, Nepal, have extensive knowledge of medicinal plants [10].

Plant parts used and their growth forms

Among the choices of plant parts, leaves, fruits, and flowers were most frequently collected and utilized. Due to their more frequent collection than roots and bark, leaves were also harvested and processed to create various mixtures. The leaves of a plant are the most sensitive because they contain the highest concentrations of bioactive secondary metabolites and play an essential role in the plant's defense system [37]. Additionally, the preparation of leaf extracts preserves the drug's active components more effectively than other plant parts [38]. In contrary, root contains more bio active compounds [39].

Herbs constituted the majority of collected and utilized species (46%), followed by trees (32.67%). As tree leaves and herbs were frequently valued and apparent trees and abundant herbs were primarily selected, ecological traits were followed in the selection of medicinal plants. However, the random selection was prevalent on other parts of the country [40, 41]. Irrespective to our hypothesis, plant collection was influenced more by the ecological traits (abundance and apparency). As herbs are simple to cultivate and abundant, they are easy to harvest, process, and prepare for pharmacological consumption [42]. It is believed that the medicinal benefits of a plant increase with its abundance [43]. Moreover, obvious or salient plants are frequently collected [8]. In addition, secondary metabolites are more abundant in herbs [44].

Medicinal plants use and sociocultural variables

Our hypothesis tested yielded significant relationship with the age and occupation group among the socioeconomic variables age, gender, education, occupation, ethnicity, and religion. Older respondents reported more plants than younger ones. It may be due to the elders' increased plant knowledge. Nonetheless, this may be more than a mere factor, as plant knowledge is linked to social context [45]. Older generations serve as custodians of traditional knowledge, are more familiar with traditional treatments, and have limited exposure to modern medical procedures [46]. It may also be attributable to the younger generation's disinterest in traditional medicine and related to the time they spend with their elders. Young people are highly mobile in pursuing opportunities [47]. Agri-businessmen reported more medicinal plants than other respondents (service men). These businessmen are locally engaged in the medicinal plant industry, local medicinal plant expert products, and food-related businesses, which may have aided them in acquiring a deeper understanding of medicinal plants. It is evident that people engaged in the medicinal plant business have more medicinal knowledge [48]. As medicinal plant use is more dependent on family background and the transfer of plant knowledge is dependent on family, business people may have had an excellent opportunity to converse about plants at home [49].

Conservation of medicinal plants and their traditional knowledge

Due to rapid population growth, poverty, a lack of valuation of ecological services, and ignorance of biophysical limitations, the area of lower vegetation (herbs and shrubs) and anthropogenic landscape have decreased due to human activities, including settlement and built-up areas. This change has altered the region's physical landscapes and ecosystem services [50]. Population of 21 species (Drymaria diandra, Curcuma caesia, Basella alba, Achyranthes bidenata, Bombax ceiba, Cuscuta reflexa, Bergenia ciliata, Carea arborea, Swertia chirayita, Butea minor, Viscum articulatum, Woodfordia fruticosa, Adina cordifolia, Premna integrifolia, Rheum webbianum, Mangifera indica, Terminalia chebula, Terminalia bellirica, Callicarpa macrophylla, Melia azederach, and Marsdenia tinctoria were reported to have declined due to land use change followed by a change in agricultural area. Evidently, land use change alters plant use patterns and promotes more use of resources from the secondary forest and the use of non-indigenous species [7].

For ethnomedicine, the sociocultural transformation may be one of the significant threats and challenges [51], which includes the migration of youth to urban areas in search of good opportunities [32] and the disinterest of young people in traditional medical practices, similar to other global records [52]. Typically, older people are the source of ethnomedicine, but sometimes, they pass away without passing on their knowledge to the younger generation, which poses a significant threat to ethnomedicine [53]. A study from Nepal revealed that youths are less interested in ethnomedicine [21], which is another threat to ethnomedicine. However, rural people prefer to retain their knowledge of medicinal plants [54]. There is a belief that sharing ethnomedicinal plant use knowledge diminishes healing effectiveness, so most local healers in Nepal wish to keep their ethnomedicinal knowledge secret. However, most of them impart their knowledge to close relatives, such as sons, daughters, and daughters-in-law.

The dominance of allopathic medicine is also a challenge for ethnomedicine, given that allopathic medicine is readily available and believed to have a rapid healing capacity [55]. Traditional healers should impart traditional knowledge to the younger generation to preserve this knowledge. The valuable knowledge of ethnomedicine should be preserved, and young people should be made aware of the ethnomedicinal system. A mechanism for intergenerational learning should be established [56] by organizing interaction programs for younger and older villagers and households.

Conclusions

We recorded 149 medicinal plants from 68 families and 130 genera used to treat 48 diseases. The most plants were used for digestion (119), while the fewest were used for genetic disorders (3). C. angustifolia was the most frequently cited medicinal species, followed by Z. officinale, A. sativum, A. indica, and O. basilicum. Our study supported the positive relationship of medicinal plant use knowledge with the elder people and people involve in agri-business. Changes in land use, population decline, and unsustainable medicinal plant harvesting practices posed the greatest threats to medicinal plant conservation in Okhaldhunga. The major threats to medicinal plants and their knowledge are sociocultural transformation, vertical transfer of plant knowledge, and youth disinterest. We suggest managing ongoing land use change and human migration and educating individuals on the traditional medical system.