Introduction

Plants have been an integral part of life in many indigenous communities, and Africa is no exception [1, 2]. Apart from providing building materials, fodder, weapons and other commodities, plants are especially important as traditional medicines. Many tribes and cultures in Africa have an elaborated plant knowledge-base [3]. Most of this knowledge is still entirely transferred orally within the family unit or community [4]. Western influences have, however, led to an accelerating decline of this tradition. For example, Western style healthcare supplied by some governments has been expanded in the last decades, but it is still often not readily available and many regions remain completely underserved. Subsequently, most rural communities still use herbal remedies as readily and cheaply available alternatives. This knowledge is however, rapidly dwindling due to desired changes towards a more Western lifestyle, and the influence of modern tourism and other agents of globalization.

During the last decades, a vast array of ethnobotanical studies from Ethiopia has been published. Most of these focused however on the northern regions [5–12], as well central and southern Ethiopia [13–26].

Various studies report on the toxicity and efficacy of Ethiopian traditional medicine [8, 27–34].

The study area

Our study was conducted in the eastern reaches of the Bale Mountains in the southern highlands of Ethiopia (approximately 6° 9'N, 40° 22'W) [35]. The study area covers an area approximately 380 km2 with elevations ranging from 1,500 m to 3,300 m (Figure 1). Mean minimum and maximum temperatures are 10.2 C° and 21.3 C°, respectively; while mean annual precipitation ranges from 68 to 93 mm largely occurring during two rainy seasons. The majority of the study area is mountainous with intact forest ecosystems [36, 37]. Most anthropogenic activities are centered on honey gathering and the collection of wood and bamboo (Sinarundinaria alpina). Some livestock grazing occurs, but generally at small scales. The study area has remained relatively preserved for two primary reasons: the topography is largely prohibitive to cultivation and there are two controlled hunting concessions (called Odu Bulu and Demaro) that provide legal protection to the forest. Trophy hunting within the hunting concessions generally occurs within a three-month period; however, both concessions maintain permanent camps and guards to protect the wildlife and habitat. Just beyond the northern edges of the study area, the landscape is heavily populated with people and livestock. The forests here have long been cleared, and barley cultivation is extensive. The southern edge of the study area drops sharply in elevation before transforming into semi-arid plains that stretch into Somalia. The steep slopes act as a barrier to human and livestock encroachment providing further protection to the study area [38]. Although the study area has significantly less anthropogenic impact than nearby Bale Mountains National Park, increasing human and livestock pressure within the study area is becoming evident.

Figure 1
figure 1

Study area.

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The Oromo

The Oromo are the main ethnic group in southern Ethiopia, including the Bale region, although members of many other peoples have settled in the area. Smaller populations are found in Somalia and northern Kenya. Barley and wheat cultivation provide most sustenance and income in Bale, with some areas receiving enough rainfall to support two harvests a year. Livestock keeping is also important to Oromo people, but occurs to a lesser extent than most areas in Ethiopia. During the time when crops are cultivated, livestock are grazed in the forest and Afro-alpine of higher elevations. Because some areas can support two harvests annually, livestock may spend as long as ten months in natural areas. During the last decades, Bale has seen profound changes, from increased access and governmental health care entering during the communist era of the 1970s and 80s, to an increase in tourism in the 1990s and a large influx of Chinese development aid in the last few years. These years have also marked a dramatic increase in human and livestock populations, and consequently land-use and conversion of the landscape. Throughout the 1980s and early 90s, Ethiopia's communist government regularly relocated people from northern regions to Bale as a means to disrupt civil opposition [39]. Since then, the current government has continued the practice on a voluntary basis as an effort to provide people access to natural resources, which have been depleted in other parts of the country. Collectively, these events have put an enormous strain on forests in the Bale Mountains, and are changing the local economy and traditional customs profoundly.

The ethnobotany of various subgroups of the Oromo has been focal point of a few recent studies [40–42].

Materials and Methods

Ethnobotanical data and plant collections

Fieldwork was carried out between 2009 by Bussmann and collaborators. To obtain information on plants used traditionally, interviews were conducted using semi-structured questionnaires [43]. Random sampling technique was applied in distributing the questionnaires. Before carrying out the interviews, an oral prior informed consent was sought from every respondent. All communities involved showed the same acceptance of the researchers, and similar in-field times were involved in the study in order to avoid possible errors in data depth.

A total of 12 lay respondents were interviewed. Access to female informants was not possible. In order to get a more detailed inventory of plant use, ethnobotanical data were collected by conducting interviews directly in the field during collection trips, and by discussing the freshly collected specimens with informants, after seeking oral consent from each respondent. This method was preferred over pure questionnaires to also get an indication for species that are not used by the community, and which are normally not mentioned during traditional interviews. All interviews were carried out in local language by native speakers, and then translated into English. Voucher specimens were collected and are preserved at the National Herbarium of Ethiopia (ADD). The identification of plant material followed the Flora of Ethiopia and Erithrea [44–50], as well as [51–53]. Plant nomenclature follows TROPICOS http://www.tropicos.org.

Results and Discussion

The Oromo in Bale had names/uses for 294 species encountered (Table 1.), in comparison to 230 species documented in the lower reaches of the Bale area [23], and 101 species in the highlands [41]. The latter study did however interview health experts, while the present work focused on the knowledge of laypeople. One hundred and sixty two species encountered in this study were classified as having no uses whatsoever, although many of them were named. Many of the identified species had multiple uses or were known provide important direct or indirect services to the community (Figure 2). Most species named (172 species) were used for livestock grazing (mostly cattle). The vernacular name "Marga" for many Poaceae simply translates to "grass", and underlines the importance of this resource. It is important to note however that 42 of these were also indicated to be important for the endemic and endangered mountain nyala (Tragelaphus buxtoni), illustrating a potential conflict between pastoralist use and wildlife conservation. A further 27 species were used as fodder for both domestic animals and eaten by wildlife. Again the vernacular names often pointed to that specific use. Argemone mexicana and similar spiny species were all called "Korehare" which translates to "spiny donkey", and all serve as fodder for donkeys. Nine species were used as poisons against carnivores. Fifty-one tree species were used as firewood, while only two served to produce charcoal. Traditional houses are to a large extent built using material from the forest, and it is not astonishing that 15 tree species were used for timber, 17 species provided material to make ropes, mostly used to tie the house posts and roof beams, and 10 species were used as thatch. A wide variety of plants was found to be employed for the fabrication of tools and household implements (3 for brooms, 4 to make beehives, 3 for tanning, 11 to make ploughs, 2 served as detergent to wash clothes). In addition forest species were an important source of nutrients, with 28 species collected as food, and 23 explicitly used for honey production.

Table 1 Plants encountered in Odo Bulu and Demaro, Bale, Ethiopia
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Figure 2
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Number of plant species used in each use category.

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A very limited number of species was used for veterinary purposes (13 species), or as human medicine (46 species). Many species however had multiple uses. Plant medicine served mostly to treat common everyday ailments such as stomach problems and diarrhea (9 species), for wound treatment and as toothbrush-sticks (6 species), as anthelmintic, for skin infections and to treat sore muscles and swellings (4 species each), or to foster hair growth, to treat colds, and syphilis (2 species each). One species was employed for female illnesses, and one to treat cancer. Interestingly, 9 species were used to treat spiritual ailments and to expel demons. In most cases of medicinal applications the leaves (26 species) or roots (15 species) were employed, while fruits (4 species), flowers (1 species) and bark (1 species) did not play a significant role.

Traditional plant knowledge has clearly declined in a large part of the research area. The most traditional groups still retain the highest knowledge of plant use for human purposes, although acculturated societies are shown to retain a much higher plant usage in order to treat common "modern" diseases such as sexually transmitted disease, as well as veterinary problems that are either stigmatized, for which western treatment does not prove effective, or for which cheap treatment cannot be found. Western style health care services as provided by governments and NGOs, in particular in rural areas, seem to have contributed to a decline in traditional knowledge, in part because the local population simply regards western medicine as more effective and safer, or as one of our Oromo informants put it "Sick people go to the clinic or cultural practitioner who prepares medicine from plants. Nowadays people mostly go to the clinic. The head of household knows herbs and they might use these, but nowadays most people prefer to go to the clinic. Traditional herbalists are already very old. The tradition is normally passed from the father to the son. Formerly people came from far like from Addis, and there is still a woman healer who is famous for treatments for example for parasites. Western medicine is more scientific and thus more reliable. Traditional medicine is often very painful, and can cause harm. Sometimes people die of traditional medicine. For their animals people prefer to go to the animal hospital. Traditional remedies are only used for rabies."

The knowledge of the Oromo population in both the highlands of Bale and the lower areas south of the massif were comparable. However, some profound differences were encountered. The Oromo of the Bale highlands did not use preparations for malaria for the simple fact that malaria does not exist in their area. Thirteen species were used as veterinary medicine by the Oromo in the study area. This is rather surprising, because [42] reported 74 veterinary medicinal plant species from the study region. Plants for the cure of venereal diseases such as Gonorrhea, Syphilis and others, were almost negligible in the present study in the Oromo area. Previous records indicate that venereal diseases were amongst the most frequently treated with plants amongst the Oromo [23, 41].

These differences might indicate a clear difference in plant knowledge between traditional healers and laypeople. Experts clearly had a much more profound knowledge than the non-experts interviewed. We must also consider disparities in floral composition and availability between the Oromo people inhabiting our study area and those that inhabit different regions and ecosystems. In the worst case scenario, the Oromo in Bale may have already lost much of the plant knowledge that previous generations relied on for centuries.