Urban green areas are important part of dynamic and complex urban ecosystem and provide significant ecosystem services. Less attention is often given to the potential urban green areas serve in urban biodiversity conservation in most developing areas. This paper identify and mapped urban green areas of Ugep, the largest ‘native’ town in West Africa and further examine the size and change pattern of the green areas in comparison to the built-up areas and exurban from 1999 to 2013. Using aerial photograph and ground truthing helped to identify and map land uses while graphs and tracing papers served in calculating the size and change pattern of the urban green areas, built-up areas and exurban. Ten urban green areas depleted by anthropogenic activities were located in the study area. The Analysis of Variance (ANOVA) tested the validity of the size and change pattern of the green areas, built-up areas and exurban. Results showed that significant differences occur in the size and change pattern among green areas, built-up areas and exurban. The area covered by the green areas, built-up areas and exurban was calculated and then converted to percentage of site covered. Green areas decrease in size from 23.65% in 1999 to 18.19% in 2013, and exurban, 60.13% to 49.01%. During the period of study, built-up areas increased from 16.23% to 32. 80%. Hence, built-up areas consistently expanded at the detriment of green and exurban areas. The vestiges of natural vegetation remain primarily along stream buffers and pristine sites. The most evident problem in the study area is that emphases are not laid on the ecological values the green areas possess hence increased built-up areas has caused biodiversity imperilment in the area under study. It is therefore recommending that conservation planning should specifically address the issue of human settlement and development to underline the values of unprotected green areas for nature conservation within the urban setting.