GeoJournal 44.1: 51–60.  1998 (January) Kluwer Academic Publishers. Printed in the Netherlands.

Indigenous knowledge of landscape–ecological zones among traditional herbalists: a case study in Keiyo District, Kenya Jungerius, P. D.; Landscape and Environmental Research Group, University of Amsterdam, Nieuwe Prinsengracht 130, 1018 VZ, Amsterdam, The Netherlands Accepted 22 November 1997 Abstract: Object of study is the insight of traditional herbalists in the landscape-ecological factors wich control the growth of the plants they use for healing their patients. The extent of this insight determines their capacity to adapt to environmental changes such as deforestation and soil degradation. This paper deals with the landscape-ecological perception of herbalists who live in an area with sharp landscape contrasts and drastic changes in landuse: the Keiyo Escarpment in the Rift which links the cool and humid Uasin Gishu Plateau at a level of more than 2600 m above sea level, with the warm and semi-arid Kerio Valley at 1250 m. The landuse changes of the last 50 years are caused by growing population density, loss of traditional attitudes towards the value of the land, and changes in forest cover. Data on local knowledge are acquired through interviews and field visits. The corresponding western knowledge is derived from aerial photographs and existing reports and maps. Six landscape-ecological zones are recognized. They are named after topography (‘wareng’, ‘mosop’, ‘soin’), vegetation (‘teguming’, ‘korget’) or landuse (‘tumdo’). These zones coincide with the units of the agro-climatic map of Kenya. Apart from geology, all the factors of the hierarchical model used in western-based landscape ecology (climate, geology, relief, water, soil, vegetation and fauna) are included in the indigenous perception of the landscape, but the hierarchical order is not necessarily the same: e.g. the herbalists assume that rock grows in the soil instead of the other way around, and that forests attract rain. From the herbalists’ point of view, deforestation and the establishment of small-holder agriculture is less serious for their trade than the replacement of indigenous trees by plantations with exotic species. They adapt to the loss of the forest by travelling to areas with comparable landscape-ecological conditions or, especially in the case of women and older male herbalists, by planting the required species in the garden. According to the herbalists, good climate and fertile soil stimulate species diversity, but best medicinal performance give plants on soils which are periodically dry. Key words: hierarchical ecosystem model, agro–climatic map, soil, deforestation

Introduction This study deals with the landscape-ecological perception of herbalists who live in an area with sharp landscape contrasts: the Keiyo Escarpment in the Rift Valley which links the Uasin Gishu Plateau at a level of over 2600 m above sea level, with the Kerio Valley

at 1250 m altitude (Jungerius, 1996). The difference in altitude is accompanied by equally drastic changes in climate, parent rock, soil, vegetation and landuse. In this area the herbalists’ insight in landscape-ecological conditions is tested against the knowledge of the author. As the latter is a geomorphologist/soil scientist, emphasis is on abiotic factors.

52 The study is part of a research programme dealing with the traditional herbalists’ knowledge of the ecological conditions of plant growth. How do they find the plants they need for their patients: is it because their teacher showed them the location, or because they were taught the growth conditions? In the latter case it is easier to adjust to environmental changes, because the herbalist can conduct a search based on ecological considerations when a location where a plant used to grow is exhausted or no longer available. The latter situation is particularly relevant for a woman herbalist who marries into a household far from the village where she was brought up and learned the trade. Ecological knowledge can be tested for every individual plant, but also on a higher level of abstraction: are the herbalists aware of the landscape as an ecosystem, and do they recognize the factors of landscape formation? Following that line of research, it is the main aim of this paper to define indigenous landscape-ecological zones which are relevant to traditional medicine. Related questions are: – How much do herbalists know of landscape-ecological conditions of plant growth (climate, landform, water, soil, etc.), particularly with respect to medicinal plant? – How does this knowledge compare with westernbased landscape-ecological knowledge? Is the indigenous concept of the plants’ ecosystems similar to ours, more restricted, or wider, perhaps including parameters not known or neglected in the western approach? – Is the healing power of a plant different in the various ecosystems and is there a relationship between ecosystem and type of disease? – When the landscape has changed, to what degree is the landscape-ecological knowledge adaptable to the new conditions? This research was carried out in 1996 when the author was temporarily attached to the School of Environmental Studies of the Moi University, Eldoret, Kenya.

Land and people The area of investigation is located in the Keiyo District of the Rift Valley Province in Kenya. From a geomorphological point of view, three main landscape components can be recognized (Figure 1): – the humid plateau, up to 2650 m high, which represents the eastern fringe of the Uasin Gishu Plateau; – the Keiyo Escarpment which is one of the highest of the Great Rift system and slopes steeply down from 2600 m to 1250 m;

P.D. Jungerius

Figure 1. View from the edge of the Uashin Gishu Plateau across the Keiyo Escarpment to the Kerio Valley.

– the gentle footslopes of the much drier Kerio Valley. The area of investigation is inhabited by the Keiyo who belong to the Kalenjin group. The Kalenjin entered western Kenya from somewhere in the north, perhaps from an area in Ethiopia north of Lake Turkana (Were & Wilson, 1984). According to Herlocker et al. (1994b), people began moving into the Kerio Valley in the 1940’s, descending from the plateau, but Chebet & Dietz (in prep.) claim that there was continuous settlement since 1750. Throughout the time of dominance of the Nandi, the major Kalenjin tribe, this was a refuge area for the Keiyo, especially the more gently sloping part of the Keiyo Escarpment from where the people could move up to the Uashin Gishu Plateau with their cows, and down to the Kerio Valley with their goats. Because even the recent history is not well known it is not possible to trace the origin of the herbalists’ knowledge. The study presented here was carried out in Kaptarakwa, a community of about 2000 farmers in a remote part of the district, on the Uasin Gishu Plateau near the edge of the Keiyo Escarpment. In the absence of adequate provisions for western-type medical treatment, sick people of this area consult traditional practitioners. Most of these are herbalists who use various parts of plants and trees to prepare their medicines. Kaptarakwa has six herbalists (four men, two women), each with his or her own practice, specialisation and secret formulae for preparing the drugs. The herbalists of this community use about 50 different plant species for their practice.

Methods and materials Data acquisition from herbalists is based on interviews and field visits. This approach demands considerable caution because the herbalists’ knowledge is

Indigenous knowledge of landscape-ecological zones among traditional herbalists

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Figure 2. Landscape zones according to indigenous and western-based classifications.

their source of income and therefore cautiously guarded. It is clear that the quality and quantity of information obtained depends on the trust the herbalist has in the integrity and good intentions of the persons carrying out the interview. For this reason, research in a community starts with a herbalist related to colleagues of the Moi University. Even so, a practitioner’s confidence can be won only by stressing time and again that we are not interested in their knowledge of plants and diseases, but only in their perception of the terrain where the plants grow. Once it is realized that there is no secret knowledge involved, other herbalists of the community join the interviews and fieldtrips. Generally, the required information is freely given, with the exception of matters touching on magic which are laughed away by the staff members who act as interpreters. Use of the vernacular is necessary in order to understand subtleties in the herbalists’ interpretations. Mr. Abraham Toroitich Kangogo is the principal informant for this paper. He was born in the Kerio Valley in 1925, and learned the trade from his father and from another practitioner who healed him from a serious disease. This was ‘when the Germans were fighting’, presumably during the Second World War. He is chairman of the newly founded Kapkee Herbalist Group which aims at coordinating the activities of the

local herbalists and enhancing their status in the community. Mr. Kangogo was the spokesman, but other herbalists participated in the interviews and field trips as far as their busy practices permitted. There is no reason to assume that the views expressed in this paper are not shared by most herbalists in the community. None of the herbalists has been exposed to western ways of landscape research, not even in the course of this study: the interviews were never permitted to turn into landscape-ecological discussions. The landscape zones recognized by the herbalists have been compared with a number of western classifications (Figure 2). To include the major landscape zones and avoid undue detail, a level of generalization was chosen which corresponds with the reconnaissance soil survey. The scales of these surveys vary from around 1:62,500 to 1:1,000,000 (Soil Survey Staff, 1961). The geological map 1:125,000 prepared by Walsh (1969) depicts three lithological units. The plateau and the upper part of the escarpment consists of Miocene lavaflows, mainly phonolites. From approximately 1900 m downward the rocks are composed of the gneisses of the Basement System. Quaternary slope deposits fill the Kerio Valley. Not shown on the map is a narrow zone on the plateau along the edge of the escarpment which is covered with volcanic ash.

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P.D. Jungerius

The classifications of agro-climatic zones and soils are based on maps prepared by Sombroek et al. (1982) at a scale of 1:1,000,000. Agro-climatic zones are a combination of moisture availability zones which are defined by rainfall and evaporation which have a relationship with vegetation, potential for plant growth and risk of crop failure, and temperature zones which are characterized by mean maximum, mean minimum and absolute minimum temperatures. The information on geomorphology and (change of) landuse was obtained by stereoscopic analysis of aerial photographs for which pictures of 1964 and 1996 were available. To find out if the herbalists recognize the same factors of landscape formation and if so, which of these factors are considered to be more important, the hierarchical ecosystem model developed for western landscapes (Bakker et al., 1981; Klijn, 1997) was used for reference (Figure 3). For the scientific names of the plants mentioned by the herbalists, see Cappon et al. (1985) and Kiplagat (1995).

Results Figure 2 combines the indigenous and western classifications. Three aspects are worked out for each of the zones: first a translation of the general description by the herbalists (with comments of the author between brackets), then in italics the importance of the zone for local medicine, and finally the western-based characterization, including geomorphology, geology, agroclimatic and soil zones. From west to east, the herbalists recognize the following zones: Wareng, a Maasai word for plateau. The Maasai used to roam this area with their herds before they were driven out by the white settlers who started largescale agriculture early this century. The Maasai belong to a different ethnic group and were much feared by the Keiyo. Like the white settlers they denied the Keiyo access to the main part of the vast Uasin Gishu Plateau. After Independence in 1963 the area was taken over by the Kalenjin, mostly Nandi and Kipsigis, who continued the type of landuse of the white settlers, with maize and wheat as the main crops. This zone has no use as a source of local medicine. It has been inaccessible for a long time, and very little of the original vegetation is left. The undulating plateau is underlain by Tertiary lavaflows including basalts and phonolites. It is agro-climatic zone III-6 which is semi-humid with the potential of dry forest and moist woodland. The soils belong to soil zone L24: well-drained deep, dark red clay over petroplinthite (rhodic Ferralsol, petroferric phase).

Figure 3. Hierarchical ecosystem model adapted from Bakker et al. (1981).

Tumdo, meaning wilderness, or area empty of human life. It was a buffer zone between the Maasai and, later, the white settlers in the west and the Keiyo in the east, Animals were protected here. Grazing was only allowed in times of bad growth elsewhere. The vegetation was also left alone, because this was a catchment area feeding water to the other areas. The present vegetation is best described as secondary forest and shrubland. This was and still is one of the main areas where the herbalists derive their medicinal plants. There is a wide variety of herbs because the soils are fertile, although they are much redder (‘chepiriret’, from ‘piri’ = red) than close to the escarpment and less sticky: ‘they dry out more quickly’. The geology is the same as in the ‘wareng’, but the relief becomes more rolling because the streams are deeper incised towards the edge of the plateau in the east. The amount of rainfall increases in the same direction. The area is classified as agro-climatic zone II-6: sub-humid, allowing moist and dry forest. It is soil zone Uh3: well-drained, deep dark reddish brown clay (eutric Nitisol). Teguming, from ‘Tegat’ = bamboo (Arundaria alpi-

Indigenous knowledge of landscape-ecological zones among traditional herbalists

Figure 4. View from the escarpment towards the eastern subzone of the ‘teguming’ (left), the farmland of the ‘mosop’ (centre) and the steep ‘korget’ (right).

na). This is the zone of the once extensive Kaptagat Forest. The high altitude allows the growth of bamboo which gave the zone its name. There are now three subzones. The forest in the western subzone which is owned by the state Forestry Department has been replaced almost completely by plantations of foreign species (mainly Cypressus lytea). The soils are red and dry out quickly. The soil along the streams is called ‘kipsiyai’ which stands for colluvium washed down from ‘bertekwo’ (eroded red soils) higher up the slope. The area is now drying up, because there was more rain in former times: ‘indigenous trees attract clouds, especially bamboo. They attract also dew when it is cold, just like a metal roof it will shed tears before the rains come’. Other good performers in this respect are ‘Lamaiwet’ (Syzigium cordatum), ‘Tenduet’ (Pygium africana), ‘Mwochet’ (scientific name not known) and ‘Emdit’ (Olea africana). The latter also holds the soil together between its horizontally growing roots and ‘makes the soil black’, i.e. it produces much organic matter. Exotic trees attract no clouds. Moreover, they have no undergrowth and water runs away along the surface leaving the soil dry. The central subzone is a 3 to 4 km wide strip along the edge of the escarpment. Forests reached the edge of the Keiyo Escarpment in former days, and were inhabited by elephant and buffalo. The forests were long ago converted to small-holder farmland. Maize and many other foodcrops are grown here. The soils are ‘meniot’ which means black and sticky, or ‘netui’ which means black and non-sticky (the organic origin

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of the non-sticky variety is known to the herbalists: remains of trees and grass are mixed with the soil, but the origin of the sticky soil as volcanic ash is beyond their conceptual horizon). The waterholding capacity is very variable. The slopes of the eastern subzone, over the rim of the escarpment, are predominantly steeper than 30° which is too steep for agriculture (Figure 4). The soils are like those of the ‘wareng’: they hold no water. The original indigenous trees are all replaced by shrubs, apart from those in the valleys which are incised in the slope of the escarpment. The herbalists realize that a dense tree cover is needed to protect the springs issuing from these valleys. The elders have always warned against cutting, and especially uprooting of trees on the slopes. Only the collection of herbs was allowed. Violators of this rule would be expelled from the community or even cursed to death in former days, but the system of communal responsibility has disintegrated because the schools teach otherwise. Some farmers are now trying to establish plots even on the steepest slopes, for maize, potatoes and beans. They don’t seem to mind that the shallow soil will disappear in a few years’ time. The herbalists describe the consequences: rainwater will no longer be absorbed by the soil and find the sources but will flow along the surface causing more erosion. The sources will dry up. The once important western subzone has lost its medicinal value because the herbs have left with the indigenous forest. Fortunately for the Keiyo herbalists, some of the plants of the original forest can still be found along the streams where planting exotic trees is not economically viable. Useful trees and herbs also remain or can be planted in the hedges surrounding the farmland in the central subzone. For this reason is deforestation and replacement with small-holder agriculture considered to be less serious for the herbalists than the replacement of indigenous trees by exotic species (the same opinion was held by Luya herbalists around Kakamega Forest: useful trees are preserved scattered between and in the fields, and medicinal herbs still grow in their shadow). Scars in the bark of the few remaining ‘Seretuet’ (Acacia abyssinica) on the steep slopes of the eastern subzone testify to the frequent sampling by passing herbalists. If they need ferns they find them here, because ‘ferns grow in rocky areas’. Medicinal herbs here are few but ‘strong’. The supply is evidently not sufficient: the herbalists travel far to collect their material in other forests. If travelling is not possible because they are too old or, in the case of women practitioners, they cannot leave the household, they will plant the trees they need in their own compound. The Tertiary lavaflows are the underlying rocks also in this zone, but they are covered near the edge of the

56 plateau by volcanic ash from Quaternary eruptions. The weathering products of this ash give the soils their dark colour and high fertility. The valleys of the streams which flow westward away from the escarpment are incised, giving the plateau in the central subzone a rolling character. The slopes of the escarpment in the eastern subzone are very steep. The ‘teguming’ belongs to two agro-climatic zones: I-7 which is the most humid due to its altitude with moist forest as the original vegetation, and the lower II-6, semi-humid with moist and dry forest. Soil zone Uh3 of the ‘tumdo’ continues in the tree plantations; soil zone Uu2 occurs in the central, agricultural zone: deep, smeary loam with a thick humic topsoil (ando-luvic Phaeozems), and soil zone M8 is found on the steep upper slope of the escarpment: shallow, rocky and stony loam (eutric Regosol, lithic phase, with rock outcrops). The recent occupation of the steep slopes of the escarpment results from the increasing population pressure. It is noteworthy that the drastic changes in landuse did not affect the name given to this zone: all three subzones are still part of the ‘teguming’! From the indigenous landscape-ecological point of view, the impressive break in slope between the plateau and the escarpment is apparently less important than the climate which in former times allowed forest with bamboo to spill over the edge. Mosop, a word without an English equivalent, meaning something like high land with aspects of coolness (2250-1900 m). The slopes are more gentle, allowing settlement and agriculture (Figure 4). There are flatter slope sections here, which the herbalists attribute to earthquakes (which is not far off the mark, because they are caused by faulting or mass movements). There used to be forests here which were not very thick, with undergrowth (on the 1964 aerial photographs this zone was largely under shrubland, but it is almost fully cultivated now). Two sacred groves, one for the conferences of the elders, the other for traditional dancing, are all that remains of the forest. It is even nowadays strictly forbidden to take anything from the groves, not even dead wood. The floor of these groves protrudes nearly one metre above the surrounding agricultural land which has been lowered this much by soil erosion after the trees were removed. Patches of reed indicate that there were water sources here before the site was cleared. The soil is too shallow now to allow water to come to the surface as springs. Conditions are different from the higher zone. The soils are ‘drier’. Still, this zone is valuable for herbalists

P.D. Jungerius because of its variety of herbs which is larger than in the ‘teguming’ above and the ‘korget’ below. The rocks are volcanic, like in the higher parts of the escarpment, consisting of basalts, phonolites and trachytes, interbedded with tuffs. It is agro-climatic zone III-5: semi-humid and suitable for dry forest and moist woodland. The soils belong to soil zone M6: shallow to moderately deep, brown, rocky and bouldery loam, in places with a humic topsoil (nito-chromic Cambisols, Lithosols, eutric Regosols and rock outcrops). Korget, a word which is composed of kor = mixture and get = tree, i.e. a transition zone (1900-1350 m). The slopes are steep and regular cultivation stops here. The shallow and stony soils are mainly used for extensive grazing. Only old women of the ‘soin’ zone below grow some millet here, because the better lands of the ‘mosop’ are too high up. This is also a dry area, with evergreen and semi-deciduous bushland (Acacia tortilis, Combretum spp., Acacia brevispica and Dodonaea viscosa are the principal woody species). The undergrowth is rather dense in the upper parts, but gradually thins out until the soil between the scattered trees is bare at 1500 m. Evergreen forest is found in the moist indentations of the escarpment slope. It is forbidden to cut the forest, because they protect the springs. Especially below 1600 m the area is dry, with the characteristic ‘kures’ (Euphorbia candelabrum) and the high chimneys of termite nests. The slopes are steep and the soils stony and rough. ‘Even the birds have a different song below this level’. Some trees in this zone provide medicine to the herbalists, but by and large the zone is of little use to them. The first cactus is encountered below 1600 m, but it has little medicinal value. The 1900 m contour marks a very important geological boundary. The Miocene volcanic rocks make place for the metamorphic rocks of the Basement System, mainly comprising gneisses and schists. The agro-climatic zone is IV-3 /4: semi-humid, characterized by dry woodland and bushland. The soil zone is M10: shallow, rocky and stony loam (chromic Cambisols, eutric Regosols and rock outcrops). To the herbalists the important geological boundary at 1900 m has meaning only because the agriculture of the more humid and relatively level ‘mosop’ changes to the non-productive, steep and dry ‘korget’. The climatic boundary they recognize at 1600 m coincides with the boundary between the agro-climatic zones IV-3 and IV-4 at 1500m. Interestingly, the sound of the birds they refer to is produced by the White-browed Sparrow Weaver (Plocepasser mahali) and the White-

Indigenous knowledge of landscape-ecological zones among traditional herbalists

Figure 5. The eroded footslopes of the ‘soin’.

headed Buffalo Weaver (Dinemellia dinemelli) which have their habitat below 1500 m (van Perlo, 1995). Soin meaning level area (1350 – 1250 m). The zone begins with a pronounced break at the base of the steep ‘korget’. The upper part is covered with large blocks and has slopes ranging from 2 to 4°. The lower part comprises the nearly level valley bottom of the Kerio River. The climate is hot and dry. The bushland of the ‘korget’ has changed into open assemblages of evergreen and semi-deciduous woodland, because of the higher quality of the soil (the dominant tree species are Acacia tortilis and Balanites aegyptica. Acalypha sp. is the major understory shrub). People practice shifting cultivation here. The soils are as red as on the plateau and carry the same name: ‘chepiriret’. The break at 1350 m marks the beginning of a zone with plants which are again of interest to the herbalists. The loss of undergrowth and the subsequent sheet erosion has few consequences for the herbalists because they use mostly bark and roots from trees. The plants from this zone are used specifically for women’s and children’s diseases. Geomorphologically speaking these footslopes are very different from the steep slopes above. The underlying geology has not changed, but the crystalline rocks are covered by slope deposits. The agro-climatic zone is V-2: semi-arid bushland (rainfall 450-900 mm). The soils belong to soil zone F13 which are welldrained, deep, red sandy loam (chromic Luvisols), but severely eroded by sheet wash and locally by gully erosion (Figure 5). They have lost their humic surface soil and are now low in organic matter. The herbalists do not recognize the characteristic shape of the alluvial fan. They attribute the low slope angles to the former presence here of the Kamnarok lake in the Kerio Valley which indeed was much more extensive in the geologic past. However, lacustrine sediments are absent. On the other hand, they are

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aware of the fact that the soil material is ‘kipsiyai’, i.e. colluvium, like in the ‘teguming’ derived from disturbed red soils (‘bertekwo’) on higher slopes. The soil is bare, due to overgrazing by the ever-present goats, but older people will not accept this explanation. In their view the degradation of the vegetation is caused by termites. The surface of the footslopes is littered with fragments of stone-age tools in many places. The fragments consist of white quartzite which is locally found, and black volcanic glass, obsidian, which presumably originates from volcanoes in the Nakuru area, more than 100 km to the south. The obsidian tools are called ‘kipsengwetiet’, meaning ‘comes from the sky’. which points to belief in a volcanic or meteoric origin. Population in those days must have been quite dense, but it left no trace in the memory of the present inhabitants, and the tools are not recognized as such.

Discussion Comparison of the local and the western classifications In western-based landscape studies, the visual landscape is commonly characterized in terms of landform and cover. Landform clearly plays a subordinate role in the indigenous classification: the important break in slope between the plateau and the escarpment features not as a boundary in the local zonation. Also, most zones comprise a number of different vegetation types. If landform and cover are not the main diagnostic criteria, what are? This is not directly clear from the names. The local zones are named after elements of topography (‘wareng’, ‘mosop’, ‘soin’), vegetation (‘teguming’, ‘korget’) or landuse (‘tumdo’). Figure 2 is more revealing. It appears that the local zones share the same boundaries especially with Sombroek et al.’s (1982) agro-climatic zones. Agro-climatic zones are defined in terms of the potential of the zone, not the actual vegetation and plant growth. It is interesting to see that the same applies to the local zones: when the indigenous vegetation is replaced by plantations or agriculture, the zone retains its original name. Figure 2 also reveals that many boundaries of the local zones coincide with the soil boundaries of the Exploratory Soil Map of Kenya (Sombroek et al. 1982), but soils are seldom mentioned by the herbalists as a differentiating criterion. The local soil classification is simple: most soils derive their name from the colour of the surface soil horizon which means that red soils on the Uasin Gishu Plateau have the same name as red soils in the Kerio Valley.

58 Comparison of local and western landscape-ecological factors The hierarchical model of landscape-ecological factors plays an important role in western landscape-ecological studies (Bakker et al., 1981; Klijn, 1997). This model comprises all the relevant abiotic and biotic elements of an ecosystem: climate, geology, relief, water, soil, vegetation and fauna (Figure 3). The downward arrows express the dominance of the upper factors over the lower factors. The upward arrows imply that there is also a reverse control of the lower factors over the upper factors. In the following we evaluate the role of each of these factors in the herbalists’ perception of the landscape. Climate The emphasis often placed on climate and the coincidence of local and agro-climatic zones suggest that climate is the major factor also in local landscape ecology. Climate clearly overrides relief in the herbalists’ perception: one of the most obvious landscape elements, the break in slope between the plateau and the escarpment, is not considered in their classification. But there is also feedback like in the hierarchical model: the herbalists realize that climate in its turn is controlled by altitude. Geology The nature of the rocks of the area has little meaning to the herbalists, even where it influences other landscape-forming processes. They are aware of geological boundaries, but their significance is subordinate to concomitant changes in other elements of the landscape which we see as the result of the change in rock type. They cannot explain the high soil fertility near the edge of the plateau where the soil is derived from the decomposition products of a volcanic ash deposit . On the other hand, they know that the soft weathering products of the phonolitic lavaflow is not very suitable for plant growth because ‘they hold no water’. Relief Although relief is in their view not a discriminating criterion in landscape zonation, the herbalists understand geomorphological processes. They are familiar with mass movements although they contribute the flat sections and steps left in the escarpment slope to earthquakes. They know that red soil comes to the surface (‘bertekwo’) when the upper soil horizons are stripped by soil erosion. They also recognize colluvium at the base of a slope (‘kipsiyai’) as a product washed from soils on higher slope sections.

P.D. Jungerius Water The herbalists are conscious of the fact that the landscape forms a hydrological system and that this system is controlled by relief: the higher parts supply the water which the lower parts need. They appreciate the often complex relationship between surface water and groundwater and are worried that the increase of surface runoff will prevent sources from being fed with groundwater. Soil The herbalists know soil-forming processes which are important for plant growth, such as humus formation. They are aware of the relationship between black colour and organic matter (‘netui’), but are ignorant of the fact that the black colour can also be caused by volcanic ash which in addition gives the soil a high nutrient content. They are familiar with the concept of waterholding capacity. The red soil dries out quicker than the black soil because texture and humus content are less favourable than in the black soil. The herbalists are only vaguely familiar with the weathering processes involved. In their view, rocks grow in the soil and are therefore part of the soil. They share this belief with many farmers, also in Europe. Vegetation The herbalists have an extensive knowledge of the vegetation, but so has every inhabitant of the rural areas here. Even children know the local names of most plants. The rank of vegetation in the hierarchical order of landscape-forming factors is as low as in the western approach: the performance of plants depends on climate, groundwater and soil quality. As in our perception, there is also reverse control: the organic matter of the soil is caused by plant growth, and the poor hydrology of the plantations are due to the imported tree species which are not adapted to the ecological conditions of the ‘teguming’. Even stronger is their belief in the control of rainfall by forests: the herbalists are convinced that forests attract rain. The question whether or not rainfall is induced by the presence of forests has not been univocally answered by western climatologists. Some agree that the presence of forests will increase rainfall, but there is doubt about the scale of this effect. Factors which could attribute to the building-up of cumulus clouds are the greater surface roughness of the forest and the greater instability of the air above it (Hamilton, 1985). Clouds and dew, to which the herbalists attach an important role, refer to the so-called occult (hidden) precipitation, involving the interception of mist by vegetation and the subsequent drip or flow of part of the condensed water down to the ground,

Indigenous knowledge of landscape-ecological zones among traditional herbalists which is believed to supply significant quantities of water in forests (Hewlett, 1967). Fauna Fauna as a landscape-ecological factor received little attention in this study. The attention drawn to the presence of chimney-building termites and specific birds in the dry ‘korget’ indicates that fauna is considered to be part of an ecosystem. The herbalists attribute the absence of ground cover in the ‘soin’ to termites which suggests dominance of fauna over plants, but so does our interpretation that overgrazing by goats is the cause of the absence of a vegetation cover.

Comparison of local classifications The distribution of the local plant names is geographically speaking very restricted: the names of medicinal plants used by the closely related Marakwet and Tugen are generally quite different (Lindsay, 1978; Delleman & Jongsma, 1993; Beentje, 1994; Herlocker et al., 1994a). In contrast, the names of the indigenous landscape-ecological zones appear to have a much wider distribution. Kaendi (1997) studied the indigenous treatment of various diseases by the Tugen people, who are also part of the Kalenjin ethnic group but living in the hills on the eastern side of the Kerio Valley. The Tugen divide their area into three zones: ‘mosop’ (the highlands), ‘kurget’ (the areas between the highlands and the lowlands) and ‘soin’ (the lowlands). The ‘soin’ is further divided in subzones: the lowlands to the west of the Tugen hills which are comparable to the ‘soin’ of this paper, are known as ‘turukwa’. According to Kaendi (1997): ‘These ecological divisions have influenced many facets of Tugen life, including the evolution of indigenous medicine. The preponderance of herbal plants in the ‘mosop’ is due to the fact that the other areas are semi-arid, while the ‘mosop’ is covered with forests, and has a pleasant climate’.

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rocky soils (Figure 4), whereas ‘soin’ is dry with eroded soils (Figure 5). The plants in these zones are exposed to prolonged dry periods with soil moisture stress and it is possible that this gives them their strength.

Conclusions The following conclusions can be drawn with respect to the research questions listed in the Introduction: – The herbalists are familiar with the ecological conditions of the growth of medicinal plants. Climate and soil are considered the most important, but the influence of relief-induced processes such as mass movements, soil erosion and colluviation, and hydrological processes such as groundwater transfer, is acknowledged. – Indigenous and western-based knowledge of the landscape are sufficiently comparable to permit cooperation of herbalists and western-trained landscape-ecologists in development projects at the spatial scale chosen for this study. On the other hand, the herbalists are aware of relationships between landscape-ecological factors which are not acknowledged in the western approach. This could give rise to misunderstandings. It is not known if the local perception of the landscape includes factors not recognized by the western landscape-ecologist. – The variety of medicinal plants and their healing power is different in the various landscape-ecological zones, but the reasons are not clear. There is also a relationship between landscape zone and type of diseases which is treated by its plants. – Their insight in landscape-ecological conditions allows herbalists to develop adaptive strategies to cope with drastic environmental changes such as deforestation and soil degradation.

Acknowledgements

The medical performance of the plants The herbalists maintain that the widest variety of medicinal plants is found in zones with a good climate and a fertile soil, such as the ‘tumdo’ and the ‘mosop’. However, the most effective medicine is derived from plants in two zones with a restricted variety of plant species: the eastern subzone of ‘teguming’ on the upper slopes of the Keiyo Escarpment, and ‘soin’, the semi-arid lower footslopes of the Kerio Valley. The reason for the superior performance of the plants in these zones could not be made clear. The eastern subzone of ‘teguming’ is very steep with shallow and

The author is endebted to Mr. Abraham Toroitich Kangogo, practitioner in Kaptarakwa, for the information he and his colleagues provided during the strenuous but inspiring walks in the steep countryside, as well as for healing him from a severe attack of arthritis. Thanks are also due to Mrs. Grace Kiplagat, Mr. Joseph Toroitich and Mr. Raymond Kandie for acting as interpreters, and to Mr. S.I. Lubira for drawing the figures. Mrs. Kiplagat translated the local plant names.

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