This study investigates the effect of urban forests in reducing particulate matter (PM) concentrations and its subsequent impact on the number of asthma care visits. Understanding the mechanisms behind the relationship between the greenness of blocking forests and the reduction in PM is crucial for assessing the associated human health benefits. This study analyzed the influencing factors for reducing long-term PM₁₀ concentrations, utilizing the vegetation index and meteorological variables. Results showed that the reduction in PM₁₀ began in 2011, five years after the establishment of the blocking forest. The annual mean PM₁₀ concentrations decreased significantly, driven primarily by summer wind speed and summer Enhanced Vegetation Index (EVI), explaining approximately 62% of the variation. A decrease in the number of asthma care visits was observed, similar to the trend of PM₁₀ reduction in the residential area and the increase in the greenness of the blocking forest. The influx of PM into the city, primarily driven by prevailing northwesterly winds, may have been mitigated by the growing blocking forest, contributing to a reduction in asthma-related medical visits among urban residents. In particular, since the onset of the COVID-19 pandemic in 2020, the increase in the PM_2.5/PM₁₀ ratio in residential areas has become more closely linked to the increase in asthma-related medical visits. It suggests another PM_2.5 emission source in the residential area. The number of asthma care visits among children (under 11) and the elderly (over 65) exhibited a strong positive correlation with PM₁₀ levels and a negative correlation with the Normalized Difference Vegetation Index (NDVI). This suggests a link between air quality improvement from the greenness of blocking forests with their capacity to capture PM and respiratory health outcomes, especially for the vulnerable groups to asthma. These findings highlight the need to manage pollutant sources such as transportation and the heating system in residential areas beyond industrial emissions as the point pollution source. The management policies have to focus on protecting vulnerable populations, such as children and the elderly, by implementing small-sized urban forests to adsorb the PM_2.5 within the city and establishing blocking forests to prevent PM₁₀ near the industrial complex.

This study investigates the effect of urban forests in reducing particulate matter (PM) concentrations and its subsequent impact on the number of asthma care visits. Understanding the mechanisms behind the relationship between the greenness of blocking forests and the reduction of PM is crucial for assessing the associated human health benefits. This study analyzed the influencing factors for reducing long-term PM10 concentrations, utilizing the vegetation index and meteorological variables. Results showed that the reduction in PM10 began in 2011, five years after the establishment of the blocking forest. The annual mean PM10 concentrations decreased significantly, driven primarily by summer wind speed and summer Enhanced Vegetation Index (EVI), explaining about 62% of the variation. A decrease in the number of asthma care visits was observed, similar to the trend of PM10 reduction in the residential area and the increase in the greenness of the blocking forest. The influx of PM into the city, primarily driven by prevailing northwesterly winds, may have been mitigated by the growing blocking forest, contributing to a reduction in asthma-related medical visits among urban residents. In particular, since the onset of the COVID-19 pandemic in 2020, the increase in the PM2.5/PM10 ratio in residential area has become more closely linked to the increase in asthma-related medical visits. It suggests another PM2.5 emission source in the residential area. The number of asthma care visits among children (under 11) and the elderly (over 65) exhibited a strong positive correlation with PM10 levels and a negative correlation with the Normalized Difference Vegetation Index (NDVI). This suggests a link between air quality improvement from the greenness of blocking forests with their capacity to capture PM and respiratory health outcomes, especially for the vulnerable groups to asthma. These findings highlight the need to manage pollutant sources such as transportation and the heating system in residential areas beyond industrial emissions as the point pollution source. The management policies have to focus on protecting vulnerable populations, such as children and the elderly, by implementing small-sized urban forests to adsorb the PM2.5 within the city and establishing blocking forests to prevent PM10 near the industrial complex.

Urban forests offer a range of environmental, climatic, economic, and social benefits to citizens. However, these effects have not been systematically measured owing to the localized nature of urban forests. This study developed a framework to assess the effects of urban forest ecosystem services and elucidate the service and benefit pathways of its indicators. Two PRISMA-guided scoping reviews were conducted using Web of Science and Scopus to identify English peer-reviewed articles (2015–2024) on the effects of urban forests and indicators. The studies on the urban forest effects were analyzed to systematically code and classify the criteria, effects, methods, and techniques based on the nature-based solutions. In terms of indicators, the ecosystem service cascade was employed to organize indicators across four pathways with structures/function, service, benefit, and value. The review revealed that temperature regulation, air pollution reduction, and carbon sequestration were the most studied effects, followed by social effects; in contrast, economic benefits and sound and noise were the least studied and assessed. Furthermore, indicator pathways were found to vary by effects. Drawing on this scoping review, a standard and expanded indicator assessment framework was developed. The proposed framework provides a decision-support tool to assess urban forest performance based on evidence, facilitating link between biophysical properties and human outcomes.