Assessing the air pollution tolerance index and anticipated performance index of some tree species for biomonitoring environmental health

The effectiveness of tree species as bioindicators/biomonitors depends on appropriate selection based on their tolerance and sensitivity to air pollution, which is usually evaluated by the air pollution tolerance index (APTI). Despite the importance of the APTI in screening tree species for biomonitoring, there are still limitations to its usefulness in green belt establishment/management. Therefore, this study combined the APTI and anticipated performance index (API) to evaluate the potential of some tree species commonly growing on the campus of the University of Ilorin, north-central Nigeria, for green belt development. The study revealed that the APTI alone is not adequate for determining the suitability of tree species for green belt development, although it can be employed to identify sensitive plants for biomonitoring. The combination of the APTI and API in this study is a practical approach to developing a sink for air pollution control. The API indicated that Vitellaria paradoxa (API = 4) is a good performer in green belt development, while Terminalia catappa, Acacia nilotica and Prosopis africana (API = 3) are moderate performers. The present study suggests that integration of both the plant tolerance and performance indices for selection of tree species is very useful for the development of a green belt.