Spatiotemporal monitoring of subtropical urban forests in mitigating air pollution: Policy implications for nature-based solutions

Air pollution remains a major global challenge in addressing environmental and health issues requiring continuous and immediate action. Nevertheless, the extensive adverse effects from atmospheric pollution are mainly experienced by communities and people in lower-and middle-income countries, such as the medium-and large-sized cities in Latin America including the coastal city of Guaruja in Brazil. Urban forests, as integral parts of the city landscape, play a crucial role in mitigating air pollution and should therefore be considered in environmental policies. This study aimed to evaluate the spatiotemporal concentrations of air pollutants using the biological monitoring method with Tillandsia usneoides L. to highlight the capacity of urban forests to act as nature-based solutions (NbS) in improving air quality and providing other ecosystem services. Based on the quantification of chemical indicators of vehicle emissions, scientifically recognized as traffic-related elements (TREs) such as cadmium (Cd), Copper (Cu) and lead (Pb) in the biomonitoring samples, the results showed spatiotemporal variations in their concentrations. This finding demonstrates that urban fragments in the low-income settlement of the city exhibited higher values for TREs during the wet season. Cu values were the highest during the wet season in all study areas, underscoring the intensity of the light vehicle fleet. Forest fragments attenuated air pollution, highlighting their importance as features of environmental planning. The identification of atmospheric pollution hotspots in the territory guided the strategic implementation of NbS through tree planting, thus promoting a healthier environment with greater mitigation potential. This study is the first in Brazil to explore the spatiotemporal relationship between air pollution and urban forests in highly dense and low-income settlements providing quantitative indicators toward the benefits of NbS.