Ecological and socio-economic impact of changing land use in Kilombero valley, Tanzania

Abstract

The study was conducted in Malinyi ward, Ulanga district in Tanzania. The aim of the study was to determine the ecological and socio-economic effects of changing land use patterns due to pastoral migration in the area. The emphasis was on vegetation changes, soil characteristics, and local people's perception about changes in natural resource utilization patterns and interaction between livestock keepers and cultivators in area that may attribute to such migration and subsequent alteration in land use types. The study area was mainly an alluvial floodplain, receiving long term average rainfall of 1000mm per annum. The predominant land uses were cultivation, grazing, and the combination of the two (agro-pastoralist). The study methods employed were fieldwork analysis for vegetation such as density, cover, production, species composition and plant recruitment and soil characteristics include pH, moisture content, organic carbon, organic matter, total nitrogen, bulk density, and texture. Interviews were conducted using structured questionnaires; both formal and informal discussions were also held with key informants including household heads, elders, government, and development agencies to get socioeconomic information in the study area. The results of the field vegetation analysis showed greater number of woody species recruitment, density, and crown cover in agro-pastoral area than the pastoral, cultivators and reserve areas. The comparison of density for three selected woody species showed significant differences (P < 0.05) for Bauhinia thonningii and Combretum tertifolium and no significant difference for Afrormonsia angolensis among four land use types. For woody vegetation crown cover of selected species showed significant difference (P < 0.05) for Combretum tertifolium and no significant difference for Afrormonsia angolensis and Bauhinia thonningii between land use types. Herbaceous vegetation biomass production and basal cover were higher in reserve area than pastoral, agro-pastoral·, and cultivators areas. When compared between land use types the basal cover of selected grass species showed significant differences (P < 0.01) for Hyperrehnia dissoluta and Panicum maximum, while there was no significant difference for Themeda triandra. All three-forb species (Bidens pilosa, Watheria indica and Flaveria bidentis) basal cover showed no significance differences between land use types. The soil characteristic of the study are(l.hadhigher moisture, organic matter, organic carbon, nitrogen content, and low bulk density in reserve area than agropastoral, pastoral, and cultivator area. The socio-economic information showed that there was increasing demand on land resources due to population increase and changing land use patterns. The cultivators have been forced to hire farmland, the fallowing period had been shortened and existence of conflicts between the cultivators and livestock keepers. This resulted in reduction of vegetation cover, wildlife numbers, low water level of Kilombero River and its tributaries. There are also mutual benefits between the three communities, the Ndamba cultivators used get livestock products and crop market, the Sukuma agro-pastoralists labour and market for crop and livestock products and the Maasai pastoralists market for livestock products and food, the major problem between them is livestock damage to farmer's crops. The study recommended demarcation of grazing land from farming land, technological support to improve soil and water conservation, crop and livestock production and development of proper marketing systems for crop and livestock products. Future research should focus on integration of crop and livestock production, protection and management of preferred plant species in the study area.