THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 17 Environmental Health Air Quality Urban parks have an established impact on air quality. Urban areas generally have lower air quality than surrounding areas; one study put the disparity at 5 to 25 times more gaseous pollutants (Heidt and Neef 2008). As a major source of tree cover in urban settings, parks have a role in removing pollutants from the air and sequestering carbon (Paoletti et al 2011). The storage of carbon alone has been estimated to have a $2 billion impact in urban areas (Nowak et al. 2013). A study in the Taipei metropolitan area shows that higher green space density (aggregating green space) has demonstrated reduced air pollution. Lower emissions influence the microclimate, such as through cooler temperatures and smaller distributions of rainfall (Liu and Shen 2014). Although the evidence supports the finding that urban green space and tree canopies improve air quality overall, the literature is less unanimous on the direct impact of tree coverage on asthma. Some evidence suggests a limited impact of park space on rates of environmentally sensitive health conditions such as asthma and suggests that prevalence of tree cover may be associated with higher allergy prevalence (Lovasi et al. 2013). Using data from a birth cohort of Black and Dominican children in New York City, they found a positive connection between tree canopy coverage and asthma rates (Lovasi et al. 2013). However, literature examining the value of a “green prescription” by comparing the tree canopy with rates of health conditions found a limited but significant relationship with lower rates of asthma (Ulmer et al. 2016). There is a relationship between exposure to air pollution and higher cardiovascular mortality and an association between green space and a reduction in air pollution. However, studies mostly examine how green space at varying densities can reduce cardiovascular risk factors; links between the size of green space, time spent in green space, improvements to air quality, and cardiovascular physiology are more tenuous (Lanki et al. 2017; Plans et al. 2019; Seo et al. 2019). Climate Adaptations Climate change has impacted the environment across geographic areas. Urban areas have experienced a well-documented increase in temperatures (McPherson 1994; Whitford, Ennos, and Handley 2001).
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