Landscaping of Residential Estates as a Mitigation Measure to Reduce Carbon Dioxide and Temperature Levels in Inner Ibadan City, Nigeria

摘要

This study assessed the spatial distribution of carbon dioxide emanation in selected residential estates and the impact of landscaping in reducing their levels in Ibadan metropolis. The study was carried out in high, medium and low commercial activity areas characterized by population density and traffic congestion within Ibadan city. CO_(2) concentrations and temperature were measured at 4 hourly interval from 9am to 5pm for a period of seven consecutive days while numbers of trees/plants (biomass density) were counted, at 21 different points from seven areas each with high, medium and low commercial activities. Measurements were carried out with the aid of calibrated portable gas meters. The means CO_(2) (ppm) were 542±95, 415±11 and 376±14 at 1.00 pm in the high, medium and low commercial activity areas respectively. CO_(2) concentrations were generally higher than IPCC value, but highest in the afternoon. Temperature values were generally higher in the afternoon in high and medium commercial activity areas, but lower in the low commercial activity zones. Significantly, density of trees in low commercial activity areas (234.3±6.7) was higher compared to those in medium (22.8±0.5) and high (24.2±0.7) activity areas respectively. An inverse correlation was observed between CO_(2) concentration and the density of trees (r=-0.456; p=0.038). The spatial distribution of CO_(2) concentration in relation to landscaping revealed that CO_(2) concentration reduces northward away from the urban core areas where there were fewer trees. The areas with low commercial activities had large numbers of trees while temperature and CO_(2) flux were lower in these areas. Temperature and density of trees contribute significantly in explaining the CO_(2) concentration (p=0.015). CO_(2) concentrations and temperature were high in high commercial activities areas in Ibadan metropolis, few or no trees were observed in those areas. Increase in density of trees could be attributed to decrease in the CO_(2) concentration. Hence, tree planting needs to be encouraged in the urban core of Ibadan metropolis to reduce air pollution.