diversity within it. Through the conservation of biodiversity not only the survival of many threatened species and habitats can be ensured, but also these valuable resources will be secured for future generations and also the well being of eco-system functions protected. In-situ is considered the most appropriate way of conserving biodiversity. Conserving the areas where populations of species exist naturally is an underlying condition for the conservation of biodiversity. That is why protected

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... areas form a central element of any national strategy to conserve biodiversity. Awash National Park (ANP) is one of the protected areas in Ethiopia. It shelters 81 mammal species such as Beisa Oryx (Fig. 1), Lesser Kudu, Waterbuck, Somme ring's Gazelle, Hamadryas and Introduction Ethiopia spans a remarkable number of the world's broad ecological regions due to its dramatic geological history, broad latitudinal spread and immense altitudinal range. This range from the depressions in the Afar (126 m below sea level) to the spectacular mountaintops of Ras Dashen in the north (4620 m) and the Bale Mountains in southeast Ethiopia (4272 m). This variety of habitats also supports a rich variety of different species which contributes to the overall biodiversity of the country (IBC 2005). Biodiversity conservation is the protection, restoration and sustainable management of wildlife and natural resources such as forests and water and the biological Abstract The study was conducted at the Awash National Park (ANP) Ethiopia, to document Invasive Alien Species (IAS) and to assess the spread of Prosopis juliflora (Sw.) DC. A total of 64 sample plots were laid systematically along the altitudinal gradient of 750 to 1916 m. Potential IAS were recorded. IAS which may threaten biodiversity of the park includes species such as Prosopis juliflora, Parthenium hysterophorus L., Cryptostegia grandiflora Roxb. ex R. Br. , Parkinsonia aculeata L., Senna occidentalis (L.) Link, Datura ferox L. and Xanthium strumarium L. Except P. juliflora and P. hysterophorus, all others were not recorded in Ethiopia as IAS. P. juliflora was recorded in three plots with cover of 1% to 10%. P. juliflora was also found spread in different parts of the park particularly following the route of cattle movement. P. hysterophorus was recorded in and around nine sample plots. Plot 46, 47 and 48 were highly infested by P. hysterophorus which covered more than 60, 70 and 80% of the ground layer respectively. C. grandiflora was recorded in 11 plots with cover ranging from 1% to 35%. In view of all the natural as well as anthropogenic threats to the biodiversity of the Park, the ANP is at high risk. The rich biodiversity needs immediate management intervention.