Global Journal of Environmental Research 4 (1): 06-17, 2010 ISSN 1990-925X © IDOSI Publications, 2010 Corresponding Author: H.P.M. Moyo, Livestock and Pasture Science Department, Faulty of Science and Agriculture, University of Fort Hare, PB X1314, Alice 5700, South Africa 6 Utilitarian Perspective of the Invasion of Some South African Biomes by Acacia mearnsii H.P.M. Moyo and A.O. Fatunbi 1 2 Livestock and Pasture Science Department, 1 Agricultural and Rural Development Research Institute (ARDRI), 2 Faulty of Science and Agriculture, University of Fort Hare, PB X1314, Alice 5700, South Africa Abstract: South Africa has one of the largest problems of invasive alien plants in the world. Invasive plant species are species that are able to survive, reproduce, spread unaided and sometimes at rapid rates across different landscapes. Invasive trees pose one of the most serious threats to nature conservation in the world. Invasive alien plants affect the capacity of ecosystems to deliver goods and services. Acacia mearnsii, an invasive plant in South Africa threatens native habitats by outcompeting indigenous vegetation for water, nitrogen and organic materials, replacing grass communities. Acacia mearnsii reduces native biodiversity and increases occurrence of water loss from riparian zones. Thus, a holistic approach is imperative for their management, that require good background information which may be insufficient and where available it might be scattered in bits and pieces. The aim of this review article is to aggregate the available scientific information on the invasion of A. mearnsii and its effects in South Africa. In order inform appropriate decision for control activities to achieve both ecological and economic effects. Key words: Acacia mearnsii %Invasive plants %Woody species %Riparian ecology INTRODUCTION Acacia species [7] through mineral enrichment associated South Africa has the largest proportion of invasive grassland by woody species is a global phenomenon, but alien plants in the world [1]. The forest plantations were the effect of such on ground water and salt fluxes remain identified as the most invaded under tree plantations [2]; poorly understood [9]. A known effect of A. mearnsii with 38% of the area under commercial forestry consists invasion is the high desiccation of soil under its canopy of alien woody species, particularly the Pinus and Acacia compare to what obtains under convectional grass cover. species [3]. Acacia mearnsii is currently considered to be This makes seed germination and vegetation a major invasive tree species in South Africa; it has succession difficult [4]. Mass of leaf litter in areas invaded more than 2.5 million hectares land space, mostly invaded by A mearnsii was reported to be greater than riparian areas, rangelands and forest [4]. Acacia mearnsii that of uninvaded area [10]; this suggests that the dense threatens native habitats by outcompeting indigenous layer appears to inhibit the establishment of native vegetation for water, soil nutrients and organic matter. It seedlings [2]. Concerns have been raised on the potential decimates grass communities, reduce native biodiversity impact of A. mearnsii as a threat to plant species diversity and increase water loss from the riparian areas [5]. Its high of the affected area and on the issue of water loss through evapotranspiration rate compared with that of native flora high levels of consumption by the invasive tree [11]. has been reported to significantly alter the hydrological Invasive plant species are species that are able to balance of the invaded areas, with noticeable lower water survive, reproduce, spread unaided and sometimes at tables [6]. rapid rates across different landscapes, they also have The displacement of native vegetation by Acacia detrimental effects on commercial plant species with species has been attributed to habitat modification by the noticeable management problems [12]. They constituted with high leaf litter decomposition [8]. Invasion of