Over the past few decades there has been an increased interest in how urban natural environments (NEs) affect health, particularly with the migration of people into cities and subsequent densification. Recently, there has been an increase in studies on associations between NEs and childhood health and development, but, to date, no systematic assessment of evidence level exists, especially not within the context of different NE exposure measurements. The focus of this research is to determine which NE measurements have been used in childhood health and development research and to assess if associations and the relative level of evidence changes with different NE metrics. Additionally, this thesis seeks to evaluate possible risk of misclassification of NE exposure due to temporal alignment issues between NE exposure and health data by analyzing general and local vegetation change in Metro Vancouver over a 15-year period.
The most common NE metrics identified in the systematic review (Chapter 2) were remote sensing derived metrics, such as the normalized difference vegetation index (NDVI) and land use/land cover datasets. These metrics were also most consistently associated to health outcomes, particularly birth outcomes and decreased ADHD symptoms. Overall, there was considerable heterogeneity within NE metrics, suggesting that more research is needed before conclusions on evidence level can be made.
Through modeling NDVI over time with the Theil-Sen estimator, it was found that vegetation remained relatively stable throughout the Metro Vancouver region, an exception being in localized areas of the southeast. Additionally, large amounts of variation were found in NDVI between years, suggesting that direct comparison of NDVI between years is not advisable. To minimize the risk of misclassification in exposure, datasets should be aligned temporally.
Ultimately, this thesis discusses and highlights the importance of careful consideration of measurement selection for NE exposure in health studies. While confirming some evidence for childhood health benefits through NE exposure, the thesis concludes that, to date, research has insufficiently considered optimal selection of NE metric and the impact of vegetation change over time. These are important consideration for improving evidence-based decisions for healthy urban planning and should be considered in future studies.Forestry, Faculty ofGraduat
