Assessing changes in urban vegetation using Normalised Difference Vegetation Index (NDVI) for epidemiological studies

Urban vegetation is an important component of healthy, livable cities and has been linked to several benefits, including improved human health outcomes, natural system regulation, and habitat provision. Understanding and documenting changes to urban vegetation is essential for planning for sustainable cities. This study focuses on identifying where and when urban vegetation changed in Metro Vancouver between 2005 and 2019 using the dynamic change approach to aid longitudinal epidemiological studies in determining accurate exposure estimates. Vegetation change was detected for three time periods: 2005-2009, 2010-2014, and 2015-2019 using normalised difference vegetation index (NDVI) thresholds. A cluster analysis of vegetation change was then conducted to identify areas of change. The results show that Metro Vancouver has gained vegetation over this 15year time period, particularly along the eastern part of the metropolitan area and along the Fraser River. Vegetation loss occurred mostly in areas under high housing demand, such as along the northern parts of the study area (e.g., the North Shore). The method demonstrated in this study provides a simple, cost-effective way of assessing vegetation change, which is an important step for understanding the relationships between urban development and vegetation and potentially related changes in human health.