The critical role of human activities in land degradation in Rwanda

Abstract

Agriculture on steep land is widespread in Rwanda. Conservation strategies, such as grass strips and terracing, were introduced by the government and international agencies to lower soil losses due to fluvial processes in this fragile setting. Minimal attention has been given to assessing soil losses due to farming activities or to developing conservation strategies to control soil erosion resulting from these human activities. This study evaluates soil losses resulting from both runoff and human activities in a densely populated region of northwestern Rwanda. During a 4-year period, 11 Wischmeier-type plots were cultivated with the typical local crops. Grass strips and grass/shrub strips were planted at 5-m intervals on eight of these plots. Five meters is the common spacing of this government-encouraged conservation practice. These strips were found to be useful for reducing soil loss from runoff, but they were relatively ineffective in curtailing soil losses resulting from human activities associated with the local farming system. The soil loss on the cultivated plots, resulting from activities such as hoeing, averaged over 68·2 t ha−1 year−1. Unless conservation strategies curtail human induced soil losses as well as those due to fluvial processes, the land resource will continue to degrade and farmland will cease to be productive in the study area.