Assessing the Effects of Urban Pollution on Native Tree Biodiversity

Thesis Abstract

Urbanization has been rapidly expanding across numerous regions, leading to increased emission of pollutants that threaten native tree biodiversity and compromise urban ecological stability. This study aims to comprehensively assess the impacts of urban pollution—specifically airborne, soil, and water contaminants—on native tree species within metropolitan green spaces. The specific objectives include determining the levels of pollution in selected sites, analyzing the diversity and health of native trees, and identifying the correlation between pollution intensity and native tree population dynamics. Employing a quantitative research design, the study targeted five major urban districts with varying degrees of pollution exposure, encompassing a total population of approximately 150 native trees across representative species such as Quercus robur, Tilia cordata, and Ulmus minor. Using stratified random sampling, a sample size of 100 trees was selected, ensuring representation across pollution gradients. Data collection entailed in situ environmental assessments, including air quality measurements (PM2.5, NOx, and SOx levels), soil analyses (pH, heavy metal concentrations), and water quality testing, coupled with detailed botanical surveys documenting tree health indicators, species diversity, and biomass measurements. Data reliability was ensured through calibration of instruments and repeated measures, while validity was enhanced by standardized protocols. Quantitative data were analyzed via multivariate techniques, including Principal Component Analysis (PCA) to identify pollution patterns, and multiple regression analysis to examine the relationship between pollution metrics and biodiversity indices. ANOVA tests were used to evaluate differences in tree health across sites. Theoretical grounding was based on the Stress Gradient Hypothesis and the Ecosystem Services Framework, facilitating understanding of how pollution-induced stress influences urban tree resilience and biodiversity. Anticipated findings suggest a significant negative correlation between pollution levels and native tree health and diversity, with higher pollutant concentrations corresponding to reduced species richness and compromised physiological status. The study is expected to contribute novel empirical evidence on pollution’s specific impacts on urban native flora, filling existing gaps in ecological urbanism literature. By integrating environmental pollutant data with biodiversity assessments, the research advances understanding of urban ecological degradation mechanisms. The main conclusion posits that elevated pollution significantly undermines native tree biodiversity and resilience in metropolitan areas. Accordingly, recommendations include integrating pollution mitigation strategies into urban planning, implementing green buffers and pollution barriers, and promoting native tree planting with pollution-tolerant species. The study advocates for policy interventions aimed at reducing specific pollutants identified as critical stressors and emphasizes the importance of continuous monitoring to sustain urban biodiversity. This research provides a critical evidence base for urban ecological management, informing sustainable green infrastructure development and biodiversity conservation policies within highly polluted urban environments.