Effects of trees, gardens, and nature trails on heat index and child health: design and methods of the Green Schoolyards Project

Abstract

Background Latinx children in the United States are at high risk for nature-deficit disorder, heat-related illness, and physical inactivity. We developed the Green Schoolyards Project to investigate how green features—trees, gardens, and nature trails—in school parks impact heat index (i.e., air temperature and relative humidity) within parks, and physical activity levels and socioemotional well-being of these children. Herein, we present novel methods for a) observing children’s interaction with green features and b) measuring heat index and children’s behaviors in a natural setting, and a selection of baseline results. Methods During two September weeks (high temperature) and one November week (moderate temperature) in 2019, we examined three joint-use elementary school parks in Central Texas, United States, serving predominantly low-income Latinx families. To develop thermal profiles for each park, we installed 10 air temperature/relative humidity sensors per park, selecting sites based on land cover, land use, and even spatial coverage. We measured green features within a geographic information system. In a cross-sectional study, we used an adapted version of System for Observing Play and Recreation in Communities (SOPARC) to assess children’s physical activity levels and interactions with green features. In a cohort study, we equipped 30 3rd and 30 4th grade students per school during recess with accelerometers and Global Positioning System devices, and surveyed these students regarding their connection to nature. Baseline analyses included inverse distance weighting for thermal profiles and summing observed counts of children interacting with trees. Results In September 2019, average daily heat index ranged 2.0 °F among park sites, and maximum daily heat index ranged from 103.4 °F (air temperature = 33.8 °C; relative humidity = 55.2%) under tree canopy to 114.1 °F (air temperature = 37.9 °C; relative humidity = 45.2%) on an unshaded playground. 10.8% more girls and 25.4% more boys interacted with trees in September than in November. Conclusions We found extreme heat conditions at select sites within parks, and children positioning themselves under trees during periods of high heat index. These methods can be used by public health researchers and practitioners to inform the redesign of greenspaces in the face of climate change and health inequities.

Climate change and physical activity: ambient temperature and urban trail use in Texas

“…Cities in warm climates can work alongside academic and civic partners to develop “Cool Corridors,” defined as a spatially continuous network of physical activity infrastructure outdoors and indoors (e.g., sidewalks, trails, open spaces, pools, gyms) combined with urban heat management strategies (e.g., tree planting, installation of artificial shade structures, construction of naturally ventilated spaces). For instance, researchers revealed that heat index—a combination term of air temperature and relative humidity—was 6 °C cooler under tree shade than unshaded areas in a school park in Austin, TX, and a larger percentage of children (64% versus 46%) were observed under tree shade in higher ambient temperatures than lower temperatures (Lanza et al 2021a ). With its surrounding greenspace and relatively high tree canopy coverage, the Ann and Roy Butler Hike-and-Bike Trail may qualify as a Cool Corridor, potentially protecting against larger reductions in trail use experienced in areas without cooling features during high ambient temperatures.…”

School Parks as a Community Health Resource: Use of Joint-Use Parks by Children before and during COVID-19 Pandemic

“…The study was part of the Green Schoolyards Project (Robert Wood Johnson Foundation, grant number 76576), which aimed to determine how green features (i.e., trees, gardens, and nature trails) in school parks impacted heat index within parks, and physical activity levels and socioemotional well-being of predominantly Latinx children from economically disadvantaged families. Further detail on the design and methods of the Green Schoolyards Project have been published [38]. Prior to undertaking project activities, we received approval of project protocols by the school district and institutional review board at The University of Texas Health Science Center at Houston (HSC-SPH-19-0502).…”

A direct observation tool to measure interactions between shade, nature, and children’s physical activity: SOPLAY-SN

“…With climate-related factors becoming increasingly recognized as drivers of PA [29][30][31], incorporating measures of heat exposure and shade during recess is particularly relevant in warm climates. For instance, in the humid subtropical climate of Austin, Texas, children were more likely to be observed under tree canopy during high ambient temperatures compared to lower temperatures, potentially seeking shade for thermal comfort [32]. Further, children's PA levels during recess have been found to be lower during the spring and summer in Melbourne, Australia [33], which may be attributable to thermal discomfort during these warmer seasons in the temperate oceanic climate.…”

“…Researchers have quantified shade using the sky view factor (i.e., fraction of visible sky) [52,53], or the amount of greenness and tree canopy via satellite-based Normalized Difference Vegetation Index [54] and classification of high-resolution aerial imagery, respectively [55,56]; however, these methods have not counted the number of individuals under shade versus unshaded for a given area. Determining individuals' interaction with nature by linking geolocated PA measured by participantworn accelerometers and GPS devices with geolocated nature is resource-intensive and requires specialized training [32].…”

“…Despite an abundance of research using direct observation to study PA at recess, the mediating factors that may explain children's PA-including interactions with shade and nature/greenspace [16,25,59]-are not well understood during this critical time for PA accrual [57]. Researchers have quantified shade [60,61] and the amount of nature [62,63] using direct observation, but these instruments are not designed to measure the number of individuals under shade versus unshaded for identified areas and have not been assessed for reliability [32,64]. The Tool for Observing Play Outdoors (TOPO) by Loebach and Cox [65] is an outdoor field observational protocol that categorizes children's activities in outdoor and naturalized play spaces to evaluate outdoor play behaviors and the environment.…”