Diversity and distribution of invasive weeds in Ashanti Region, Ghana

Weed invasion presents a serious threat to Ghana's agriculture, forestry and economy, hydropower generation and drinking water supply systems. This notwithstanding, information on the diversity, modes of introduction, spread and impacts of invasive weeds is scanty. This study sought to determine the diversity and distribution of invasive weed species in the humid forest environment of Ashanti Region, Ghana. The study involved field surveys, species identification and sample collections extending from March, 2003 to February, 2004. A total of 43 species belonging to nineteen families, 41 genera and six life/growth forms were identified in five different habitats namely: cultivated, degraded, aquatic, ruderal and forested. Degraded habitat recorded the highest species richness of 31 species while cultivated and forested had the least numbers of 24 and 22 species respectively. Statistical analysis of the distribution of species in these habitats however, did not show any significant differences (P > 0.05), suggesting the susceptibility of most ecosystems in the region to weed invasion. The dominant invasive weeds were Chromolaena odorata (L.) King & Robinson (12.71%), Centrosema pubescens Benth. (10.42%) and Rottboellia cochinchinensis (Lour.) Clayton (6.39%). The results revealed the growing menace of alien weed invasion in the region and the country as a whole.