Shasha Forest Reserve, Osun State, Nigeria, was assessed for tree species diversity, conservation status and density pattern. Landsat satellite images of the forest reserve were acquired for 1980, 1990, 2000 and 2010. All were obtained from the Global Land Cover Facility (GLCF), an Earth Science Data Interface. This involved monitoring land use/land cover change, mapping distributions of various tree species, and defining management zones. Groundtruthing  was done to ascertain the information obtained from the images using multistage (3-stage) sampling technique for data collection. The results predict that forest cover will continue to decline in the future (an average number of 323 trees per hectare with 68 species were encountered in the current study as opposed to an average of 826 trees and 112 species from previous studies), while agricultural area, especially in the buffer zone, will significantly increase. In addition, protected areas in the south of the reserve contain relatively high to high suitability for landscape species (the species richness index obtained was 10.444) such as Antiaris africana, Celtis zenkeri, etc; while protected areas in the northern part provide relatively low suitability due to intensive human pressures. However, further clearing of the forest could jeopardize the viability of rare trees and animal species. The outputs of geo-informatics applications provided valuable inputs to formulate a long-term management plan for the forest because this is an important and the only remaining viable forest reserve in the state. This study therefore provides a baseline of information on the use of geo-informatics systems in monitoring the diversity of forest reserves in developing countries and its potential to encourage conservation efforts through enrichment planting of rare tree species, which are capable of bringing back the animal species in the ecosystem