Medicinal plants and their economic value in Kakamega Forest Ecosystem: A case study of sustainable land/forest project in Western Kenya

Forest Management of ecosystems plays a fundamental role in providing essential goods and services to rural communities. However, there has been a reduction in the natural forest cover due to resource utilization pressure. The pressure on forest resources is catalyzed by the expansion of markets for forest products, agricultural expansion and escalating poverty levels. An upsurge in the number of users of herbal medicine in urban and rural areas has increased the pressure on the forests, while modernization and change in lifestyle have led to the loss of traditional knowledge associated with medicinal plants utilization and conservation. No detailed economic evaluation of medicinal plants has been undertaken and the current illegal, unregulated and unreported exploitation of medicinal plants has led to overexploitation and loss of biodiversity. A better understanding of the abundance, distribution, uses and economic value of medicinal plants is important for the sustainable exploitation and conservation of forests. The study covered four forest blocks of Kakamega, North Nandi, South Nandi and Kibiri to determine plant species diversity, and their distribution in the disturbed and undisturbed areas of the forest; assess knowledge, utilization and economic estimate by willingness to-pay approach of medicinal plants to communities adjacent to the Kakamega Forest. Value chain analysis had been conducted for medicinal plants and forest user groups from Community Forest Association (CFA) had been trained in product development and access market were used in the study. Experimental Plot techniques were also used to gather ecological data on the frequency, density, diversity and distribution of the plants, whereas key informant interviews, focus group discussions and household interviews were utilized to gather information on ethnobotanical knowledge and household socioeconomic data. Thirty-two key species of medicinal plants were identified and used by local people around the Kakamega forest ecosystem. Forty-seven percent (47%) of these were trees, thirty four percent (34%) were shrubs, sixteen percent (16%) were herbs and climbers three percent (3%). Seventy percent (70%) of the medicinal plants were within the forest and thirty percent (30%) were outside the forest. The three most dominant families were Euphorbiaceae , Piperaceae and Fabaceae with leaves as the most common plant part used constituting 31 % (n=26) of the preparations, followed by roots with 20% (n=17),bark with 14% (n=14), fruits with 11 % (n=9), seeds having 11% (n=9), flowers 2% (n=2) and sap 2 % (n=3). The economic benefits generated from the medicinal plants within the forest ecosystem services in the Kakamega-Nandi landscape in terms of direct use value was about KES 601,918,256 ( ≈ USD 5.19 million) per year, while indirect use value was KES 317,288,046 ( ≈ USD 2.74 million) per year. Indigenous knowledge of the medicinal uses of the plants, their commercial aspects and distribution trends in the forest provision of wide scope for understanding relevant market systems may be tapped for decision support in rural health service planning


INTRODUCTION
Sustainable land and forest management have great potential to restore biodiversity, reduce environmental degradation, and assist smallholder farmers to achieve food, water and income security. The forests worldwide cover close to 31% of the earth's land area, and about 240 million people live in and around these forest ecosystems (World Bank, 2003;FAO, 2010). In Africa, forest ecosystems contribute about 17% of the world's forest land size and they are the source of livelihood for the adjacent communities (Schippmann et al., 2006). According to the United Nations, the world loses 4.7 million hectares of tropical forest every year while Kenya loses 12,000 hectares of forest each year. Despite all these threats, it is estimated that about 80% of the Asian and African population use traditional medicine and products derived from forests for their healthcare needs (Oyebode et al., 2016). In Africa, some of these plants are an essential source of curative, preventive remedies for various ailments (Sindiga, 1995;Villena-Tejada et al., 2021) and also for preventive therapy for human beings (Hassan, 2020). For decades, knowledge of medicinal plant species has existed in the majority of African cultures (Sindiga, 1995). In Uganda and Ethiopia, about 45 to 70 % of people are more likely to choose traditional medical care than conventional medicine (Tran et al., 2016). In Kenya the rural areas depend on traditional medicine for their healthcare needs (Owuor & Kisangau, 2006;Kigen et al., 2013) with plant medicine being practiced continuously long period (WHO, 2013). Furthermore in Kenya, 70% of the people use local homemade remedies as their first source of medicine, while more than 90% use plant related remedies at one time or another (Mbuni et al., 2020). Currently the Government of Kenya has taken steps of facilitating the restoration of forest resources and increase the forest cover to 52,276.43 km 2 under forest representing 8.83% up from 6% (MEF, 2022) with close to 3.6% of Kenya's Gross Domestic Product being derived from forests through direct and indirect contribution to the local and national economies (Republic of Kenya, 2014). Hence the need to conserve the Kakamega forest which is known to be the easternmost fragment of Guinea -Congolean lowland rainforest belt, stretching from Kenya across Uganda, East and Central Africa to the West African coast (Wagner et al., 2008). The Kakamega forest ecosystem is currently affected by agricultural encroachment which has led to large-scale degradation in recent years, characterized by illegal tree-felling and charcoal-burning firewood collection, forest grazing, and unsustainable harvesting practices like debarking trees. In Kakamega and Nandi forests, there is a very high demand for the forest products like firewood, grazing, herbal medicine, wild fruits, wild vegetables, bush meat, honey, charcoal, thatch grass and ecotourism. In addition, the current illegal, unregulated and unreported exploitation of medicinal plants may lead to overexploitation and loss of biodiversity with no detailed documentation of medicinal plants, their use and economic values. Hence the need for documentation of medicinal plants whose use has been growing in and the need to transform them into a commercial enterprise. This paper further presents the economic value of medicinal plants within the Kakamega forest as a way of demonstrating the linkage between conservation and sustainable utilization.

Study Area
This study was done within four forest blocks and the adjacent communities living around the Kakamega forest ecosystem in Kenya. The area of ecosystems covered comprises three counties namely Kakamega, Vihiga and Nandi Counties in Kenya (Figure 1). Kakamega forest ecosystem covers a total area of 240 km 2 and holds about 450 species of trees, most of them indigenous. The ecosystem has dense indigenous forests covering 11,345 ha; semi-dense indigenous forest, cover 2,705 ha while plantations cover 832 ha, scattered trees, and glades cover 1,557 ha and cleared or cultivated areas cover 2,002 ha. At an average altitude of 1580m above sea level, the Kakamega forest receives more than 2000mm of rainfall per year. The mean temperature varies between 26-27 o C while at night it is 13 o C. The forest receives an average of 2080 mm of rain per year. Rainfall is bimodal with the heaviest fall in April and May (during the "long rains"), with a slightly drier June and a second peak of rain roughly in September to November (the "short rains"). January and February are the driest months. The forest hosts tree and shrub species of Congolean lowland forest affinities, including a number of endemic plant species, mostly ferns and orchids.

Design of Study
The study focused on four forest blocks of Kakamega, North Nandi, South Nandi and Kibiri to determine plant species diversity, and distribution; assess knowledge, utilization and economic estimate by willingness to-pay approach of medicinal plants to communities adjacent to the Kakamega Forest. The line transects were made with experimental plots done along each forest block to gather plant species data on frequency, density, diversity and distribution of the plants. The contingent valuation method (CVM) was applied to estimate local communities' willingness to pay (WTP) to support the conservation of Kakamega, Kibiri, Nandi North, and Nandi South forest ecosystems for medicine. CVM surveys were conducted according to guidelines suggested by Whittington (2002), Hanley et al. (2007), Ojeda et al. (2007) and Riera and Signorello (2013). In personal interviews, a hypothetical conservation scenario was described and respondents were asked to state their maximum contribution to a local fund to ensure the continued provision of services or the existence of the forest. The payment vehicle was an annual contribution to a community development fund. This payment vehicle was adopted because the local people in Kakamega, Nandi North, and Nandi South forest ecosystems often contribute to local community infrastructure projects; for example, school classrooms are funded through the "pool together" approach popularly known as Harambee. An openended value elicitation technique was adopted with a checklist of the amount on the questionnaire, and the respondent was asked to state the maximum amount he or she would be willing to pay for each of the services. To minimize the problem of free riding, the respondents were provided with a range of monetary values from KES 100 to KES 15,000. These values were derived from Focus Group Discussions on the minimum and maximum amounts local people could pay for voluntary contributions in local fund raising (Harambees). Frequency distributions for the maximum WTP for each service were determined. The mean and the median of the sample were computed using the descriptive functions in SPSS (IBM version 20). To obtain the aggregate population WTP, the sample mean was multiplied by the population size (Hanley et al., 2007;Riera & Signorello, 2013). This is equivalent to the horizontal summation of individual willingness to pay across individuals who constitute the total population adjacent to the Kakamega, Nandi North, and Nandi South forest ecosystems.

Data Collection and Analysis
Primary data collected included the 1) local name of plant; 2) disease and condition treated by plant; 3) plant part (s) used for the treatment; 4) preparation method; 5) the indigenous, common and scientific name of the plants and their willingness to pay to conserve medicinal plants. The results were summarized in unidimensional tables to identify the medicinal plants that are most used by the respondents. The collected ethnomedicinal data were analyzed using different quantitative analyses, including relative frequency citation (F), Species prevalence (SP) use value (UV) of medicinal plants among communities living around the Kakamega ecosystem (Tardío & Pardo, 2008).
Complete information about each plant species includes botanical name, family, common name, part used, either utilized to treat human or animal diseases or both, and their recipes are listed in Tables 2 and 3.

Taxonomic Diversity, Life Forms and Plant Medicinal Applications
Thirty-two key species of medicinal plants were identified and used by local people around the Kakamega forest ecosystem. The thirty-two plant species with medicinal values were found to be distributed within 24 plant families ( Figure 3).  Forty-seven percent (47%) of these were trees, thirty-four percent (34%) were shrubs, sixteen percent (16%) were herbs and climbers three percent (3%) (Figure 2). Seventy percent (70%) of the medicinal plants were within the forest and thirty percent (30%) were outside the forest.

Total Annual Economic Value of Medicinal Plants Extracted by Households
The annual economic values were based on the willingness to pay methods which provide strict measures of economic values, which are based on peoples' willingness to pay for a product or service. This is equivalent to the horizontal summation of individual willingness to pay across all who constitute the total population adjacent to Kakamega, Nandi North, and Nandi South forest ecosystems. The monetary value for the local community on medicinal plants in terms of direct-use value for communities in Kakamega, North Nandi, and South Nandi was aggregated to the value of ≈ KES 0.6 billion and the indirect use value as ≈ KES 0.3 billion (Table 4).

CONCLUSIONS
In conclusion, there it is evidenced from the study that there is sufficient indigenous knowledge among the community around the Kakamega forest about medicinal plant species. These medicinal plant species contribute not only to the sustainable provision of community health care but also have a high potential for economic well-being at the household level if conserved. Further its shows that much of this knowledge is still held mainly by a few elderly people and with the growing    interest; unlocking such knowledge from the control of a few to the wider population through an "accelerated" social construction process such as through sustained public awareness campaigns, should be encouraged. The indigenous knowledge of medicinal plants has a very high potential for boosting economic empowerment of the counties and local community surrounding the forest ecosystems hence the need to the conservation of medicinal plants from exhaustive utilization in-situ and ex-situ.