A study on the plant diversity and invasive alien species encroachment was carried out in the Black River Gorges National Park was carried out in 2006 as part requirement for a masters programme in management of biological diversity.Plots of 20 X 10 m were randomly selected and all plants were identified up to the genus level and DBH were measured.Plants were classified as either natives or aliens and were analysed statistically. Results showed that alien encroachment is very significant and concluded that if nothing is done to stop the invasion, there will be significant loss of biodiversity...