Riverine forest in the Jubba Valley: A vegetation analysis and comments on forest conservation

Abstract

BIOGEOGHAPH/A — vol. XIV — 1988 (Pubb/ioato fl 31 clicembre 1990) The Biogeography of Somalia Riverine forest in the Jubba Valley: A vegetation analysis and comments on forest conservation JANE MADGV/ICK Somalia RE.S‘€fl7‘Cl.7 Project, Ecology and COIZS€I‘1JcZl‘Zi07Z Uzm‘, UI2z'1Jer5z'ty College London WC1E 6BT, UK SUMMARY Detailed vegetation surveys were carried out in two riverine forest areas in the Jubba Valley, southern Somalia. Results of an ordination and classification suggest that the forests can be split into several soil/ hydrological types with characteristic species. Variation in composition within the forests is strongly relat— ed to distance from the river edge. There was evidence of regeneration of forest trees and shrubs through- out the study areas although several tree species were extremely scarce. The forests share many common elements with those of the Tana river in Kenya and are most similar to the more mature levee forests. Changes in river flow caused by the proposed dam at Baardheere are likely to cause gradual changes in the composition and structure of floodplain forests. Greater impacts on the forest are likely as a result of agricultural settlement in the valley. It is recommended that Shoonto and Barako Madow forests should be protected from any further degradation since they are the largest and most intact forests left in the Jubba floodplain. INTRODUCTION Most of the remaining forests in East Africa are small and fragmented and few are effectively conserved. Recently, there has been an acceleration in the loss of tropical moist forest along perennial rivers as a result of water resource development and the spread of agriculture (Andrews et al. 1975, Hughes 1984). Although the local knowledge of natural resources in these riverine areas is great, agricultural projects and foreign-aided development schemes usually fail to consider or make use of this knowledge. Assessment of the agricultural suitability of the floodplain areas is therefore rarely com- plemented by an assessment of the local and national values of natural eco- systems. Detailed studies of floodplain ecology are needed to predict the likely effects of destroying floodplain habitats, provide guidelines for sustain- able agricultural use and point to the benefits of conserving scarce natural resources. There is a great diversity of forest types along river courses in Africa, depending on the local physical and climatic conditions (Hughes in press). Here, I assess the current status and composition of the least-known and northernmost floodplain forests in the East African lowlands, those of the Jubba Valley, Somalia. Little attention has been paid to the floristic composi- tion of these forests. Italian foresters visited the Middle and Lower Jubba in 67