Landscape Survey, Land Evaluation and Land Use Planning in South Cameroon1

Part II: Symposium LANDSCAPE SURVEY, LAND EVALUATION AND LAND USE PLANNING IN SOUTH CAMEROON1 B.S. van Gemerden2, G.W. Hazeu3, P.W.F.M. Hommel4, A.J. van Kekem4, J.C. Ntonga5 and M.J. Waterloo3 SUMMARY A landscape ecological survey at reconnaissance scale (1 : 100 000) was conducted in the Bipindi – Akom II – Lolodorf region in south Cameroon. Joint descriptions of landforms, soil and vegetation were made along transects laid down in ecologically homogenous aerial photo interpretation units. Seven landforms, four soil types and seven vegetation types were discerned and integrated in one landscape ecological map. Subsequently a land evaluation was carried out on the basis of the survey data. Five major land utilisation types have been studied of which conservation of biodiversity, timber production in natural stands and shifting cultivation are treated in this paper. Land suitability is evaluated by comparing the land use requirements with the land qualities. The results are presented as land suitability maps showing the physical potential of the area for each of the land uses. These maps provide a basis for sound land use planning in the area. Keywords: landscape ecology, land evaluation, land use planning, rain forest, Cameroon. 1. INTRODUCTION Land use planning is needed when land is becoming scarce and conflicts may arise between different land user groups. In south Cameroon, as in many other tropical forest areas, land is becoming exceedingly scarce and the various types of land use seem hard to reconcile. Land use planning is the systematic assessment of the potential of land and water and selects the land uses that will best meet the needs of the actors involved while safeguarding the resources for future use (FAO, 1993). The whole land use planning process is long and complex and involves land users and policy makers. It involves the integration of information about the suitability of land and the knowledge of different technologies. Demographic, social and economic aspects are incorporated into a policy supported by the government. Furthermore, the demands for alternative products or uses and the opportunities for satisfying those demands for available land, now and in the future, are taken into account. The aim of land evaluation is to provide a scientific basis for questions related to land use planning. It predicts land performance, both in terms of expected benefits from and constraints to productive land use, as well as the environmental degradation due to these uses (Rossiter, 1996). Basically the land evaluation should provide an answer to three questions (FAO, 1976): · Which types of land use are relevant in a given area? 1 This contribution will also be published in Foahom et al. (2001). 2 Tropenbos-Cameroon Programme. Present address: Plant Taxonomy Group, Wageningen University, Gen. Foulkesweg 37, Wageningen, the Netherlands. 3 Tropenbos-Cameroon Programme. Present address: ALTERRA, P.O.B. 125, Wageningen, the Netherlands. 4 ALTERRA, P.O.B. 125, Wageningen, the Netherlands. 5 Tropenbos-Cameroon Programme, P.O.B. 219, Kribi, Cameroon. 17 Sustainable management of African rain forest · What requirements should be met for the successful implementation of these land uses? · Where can these requirements be fulfilled? To address these questions land characteristics need to be described, mapped, and interpreted in terms of suitability for the relevant land utilisation types. A landscape survey, resulting in a map, provides the starting point for this procedure. 2. RESEARCH SITE The Forest Land Inventory and Land Evaluation project (Lu1) of the Tropenbos-Cameroon Programme (TCP) conducted a landscape survey and subsequently a land evaluation of the Bipindi – Akom II – Lolodorf area in south Cameroon (van Gemerden and Hazeu, 1999). The research area covers 167 000 ha and is situated in south Cameroon at approximately 80 km East of Kribi (2°47’ - 3°14’ N, 10°24’ - 10°51’ E). The climate is humid tropical with two distinct wet seasons (August - November, March - May) and two drier seasons, related to the movement of the intertropical convergence zone over the area. Average annual rainfall shows a decreasing trend in an easterly direction with values ranging from 2836 mm y-1 in Kribi to 2096 mm y-1 in Lolodorf and 1719 mm y-1 in Ebolowa (Olivry, 1986). Figure 1 shows the rainfall distribution in the area. The rainfall seems to be influenced by the topography. Relatively low rainfall totals were observed in the lowland and highland zones, whereas higher values were observed in the central zone where orographic rainfall seems to be significant (e.g. along the Akom II – Lolodorf axis). Evaporation totals obtained from three catchment studies with different land use (e.g. virgin forest, selectively logged forest and shifting cultivation, Waterloo et al., 2000), seem to vary within a rather narrow range (1200-1300 mm y-1) in spite of the differences in land use. This suggests that the intensity of the present land use conversions (generally less than 30% of the rainforest area is affected) does not result in a significant change in basin evaporation. Spatial streamflow patterns therefore reflect the variation in rainfall, rather than the type of land use, with the highest runoff generated in the area along the Akom II – Lolodorf axis (800-1000 mm y-1 versus less than 600 mm in the western lowland and eastern highland plateau areas). Air temperature shows little variation over the year (25.0-27.5 °C in Kribi) and relative humidity remains high throughout the year with minimum values of 70% in Kribi and 62% in Ebolowa. Wind speeds are generally low (< 4 m s-1) and the wind direction is predominantly Southwest to West (Olivry, 1986). The natural vegetation is tropical moist evergreen forests of the Guineo-Congolian domain (Letouzey, 1985). In many places shifting cultivation and logging have caused forest degradation. A total of 14 370 persons were included in the 1999 census of the area (Lescuyer et al., 1999). Average population density in the area is low, i.e. 8.6 persons per km2. Population growth is estimated to be marginal (+0.4%). Bantus belonging to the Bulu, Fang, Bassa and Ngumba tribes, form the majority (> 95%). They live in villages along the main access roads and practice shifting cultivation. In addition the collection of non-timber forest products (NTFPs) is important. Bakola (or Bagyeli) pygmies form a minority (2-4%). These forest dwelling hunters and gatherers are still rather mobile, despite processes of sedentarisation (Biesbrouck, 1999a). They practise some shifting cultivation, although the scale is limited if compared to that of their Bantu neighbours. Forest products and services are essential to Bagyeli survival, but their availability is seriously threatened by the expansion of the area under cultivation and particularly by logging activities (Biesbrouck, 1999b; Booijink, 2000). 18 Part II: Symposium Figure 1. Average annual rainfall (in mm) in the TCP area, compiled from rainfall data collected at 11 stations in the area over the period 27 November 1995 – 26 November 1997 (Waterloo et al., 2000). The main economic activity in the area is timber exploitation. Most of the area has been logged, and some parts at least twice. The logging involves the use of heavy machinery for road construction and log extraction. Present logging activities focus on Azobé (Lophira alata, 60% of the extracted volume), Tali (Erythrophleum ivorense) and Padouk (Pterocarpus soyauxii). The logging intensity is low, i.e. 10 m3 ha-1 or 0.7 tree ha-1. The felling and extraction of the logs are estimated to physically affect less than 15% of the forest surface, however, locally much higher disturbance rates have been observed. 3. LANDSCAPE SURVEY Tropenbos has developed a common methodology for land inventory and land evaluation to contribute to systematic and interdisciplinary research and subsequent sound land use planning (Touber et al., 1989). The methodology follows an approach in which the landscape is seen as a fully integrated entity that can and should be studied as a whole (e.g. Breimer et al., 1986; Hommel, 1987; Küchler and Zonneveld, 1988; Zonneveld, 1995). Based on the size of the area and the need for detail in the land evaluation, a landscape ecological survey at scale 1 : 100 000 (reconnaissance scale) was carried out. Black and white aerial photographs (scale 1 : 20 000) of 1983-‘85 were used to discern tracts of land that are ecologically relatively homogenous. Preliminary maps on landforms and vegetation were drafted and provided the basis for stratified sampling in the field (Touber, 1993). Ecological relevant data on soil, vegetation, geomorphology and land use, as well as geological, hydrological, faunal and other appropriate land attribute information were collected in selected sample sites. In addition, the 19 Sustainable management of African rain forest relevance of the boundaries of the photo interpretation units was determined. Transects of one to two kilometres and perpendicular to the contour lines were laid down in the most important and widespread land units. Along the transects observations were made on topography and landforms. Three to seven observation points were selected for detailed soil and vegetation sampling. The localities were selected as being representative (with respect to the land unit concerned) and homogenous (with respect to vegetation structure) and are located at different topographical positions to detect possible repetitive sequences (‘catenas’). The described land

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