Air regulation service is affected by green areas cover and fragmentation: An analysis using demand, supply and flow during COVID-19 quarantine

Abstract

Urban green areas are a potential supplier of air quality regulation service. However, research to date has mostly focused on the effects of the amount of these areas, with few studies evaluating how configuration aspects, such as spatial fragmentation, affect air quality services. Even less is known about how this service varies with decreasing pollutant emissions. Here we fill these research gaps by testing the contribution of green areas composition and configuration in reducing air pollution, before and during the COVID-19 quarantine period, in the largest city of the Global South (São Paulo, Brazil). We relied on a model selection approach using hourly concentrations of different pollutants (CO, NO₂, PM_2.5, and PM₁₀,) as response variables. As predictors, we consider meteorological variables, the amount and fragmentation of green areas (related to air quality regulation supply), the quantity of vehicle emissions (proxy of demand pressure), all this at different spatial scales (proxy of pollutant flows from emission to supply areas). Our results showed that higher tree cover and lower vehicular emissions decreased concentrations of CO, NO₂ and PM. Air quality regulation was higher in periods of low demand (start of quarantine), when compared to periods of high demand (before and the last part of quarantine). Lower levels of pollutants were associated with greater amounts of green areas at scales of up to 1,000 m from the air quality monitoring station. This indicates that the presence of green areas can have positive effects on air quality at distances of up to 1,000 m from the sites where pollutants are emitted. Our results show that to enhance air regulation services in large urban areas, it is important to maximize the amount of green areas and minimize their fragmentation, beyond the reduction of vehicular emissions.