Table 1.

Overview of the exposure categories.

Nature-based ECE	This category represents studies with a higher exposure to nature. These ECE settings would integrate rich and diverse natural elements in their environment and children would spend most of their ECE time outdoors. Examples of a typical nature-based ECE environment may include: wooded areas, forest, trees, hills etc. ECE practitioners would be present and may lead on formal and informal educational activities that involve/incorporate nature.
ECE natural playgrounds	This category includes studies that utilize interventions that enhanced the nature in the playground or where natural playgrounds were compared to traditional playgrounds. Children would typically spend less time outdoors in nature in these studies.
Natural elements within ECE	This category represents a lower exposure to nature and included studies (mostly cross-sectional in design) that looked at the association of specific natural elements, such as trees, vegetation, hills, grass, etc., or specific features or quality of the playground on specific health outcomes.
Garden-based interventions	This category represents studies that included an intervention with a garden component and was delivered within an ECE setting.