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Green Coverage
Metadata
Variable Definitions:
All Green Coverage: the share of land surface covered by green vegetation including tree canopies, public greenspaces, sidewalk plantings, green roofs, and residential gardens.
Public Access Park Green Coverage: the share of public access park land covered by green vegetation such as grass, meadows, and tree canopies in a given area. Public access parks include local parks, natural areas, regional open spaces, and regional recreation parks, but do not include golf courses and schools.
Source:
Original Data pulled from The National Agriculture Imagery Program (NAIP) in Google Earth Engine Datasets. Data calculated and processed by Jiyoon Kim
Years Available:
2009, 2012, 2014, 2016, 2018, 2020, 2022
Methodology Note:
The original data comes in raster images with a 0.6m resolution for the years 2016-2022 and with a 1m resolution for the years 2009-2014. Our team calculated the Normalized Difference Vegetation Index (*NDVI) and determined the share of the area covered by vegetation (NDVI value above 0.2) in a given area.
Why are these variables important to measure?
Green coverage in an area plays a key role in heat mitigation, energy consumption reduction, stormwater management, and the promotion of physical and mental health. In Los Angeles County, low-income neighborhoods can suffer more intense effects of heat waves in part due to the unequal distribution of vegetation cover. With an unequal distribution of public green spaces, street greenery, and differences in green space by residential type, some Angelenos may find themselves without access to natural features that provide physical shade or cool the environment. For example, single-family houses often have the space and facilities to cultivate private garden spaces covered with various plants, whereas multi-family housing in densely populated neighborhoods may lack these same opportunities to create such spaces.
Land surface green coverage is a crucial metric in landscape ecology, quantified using the Percentage of Landscape (PLAND). This measure calculates the proportion of land occupied by a specific type of land cover, such as vegetation. Green coverage includes various forms of greenery, such as tree canopies, public greenspaces, sidewalk plantings, green roofs, and residential gardens. This metric not only reflects how much green space is created via urban design, but also indicates the constant maintenance and quality of the greenery. Consequently, green coverage serves as a comprehensive measure of the presence and health of greenery in urban environments.
Green coverage is measured through the Normalized Difference Vegetation Index (NDVI), which quantifies the presence and health of vegetation on the land surface. It is calculated using the reflectance values of near-infrared (NIR) and red light (RED) from satellite or aerial imagery. NDVI can be affected by various factors, including human activities, rainfall, temperature, and air pollution at the time of satellite imagery.
Written by Jiyoon Kim
Citations:
Connolly, R., Lipsitt, J., Aboelata, M., Yañez, E., Bains, J., & Jerrett, M. (2023). The association of green space, tree canopy and parks with life expectancy in neighborhoods of Los Angeles. Environment International, 173, 107785. doi:10.1016/j.envint.2023.107785
Environmental Protection Agency. (2021). Using trees and vegetation to reduce heat islands. United States Environmental Protection Agency. Link
Esri. (2024). NDVI function. NDVI function—ArcGIS Pro | Documentation
Herold, M., Couclelis, H., & Clarke, K. C. (2005). The role of spatial metrics in the analysis and modeling of urban land use change. Computers, Environment and Urban Systems, 29(4), 369-399. doi:10.1016/j.compenvurbsys.2003.12.001
Kim, D., & Ahn, Y. (2021). The contribution of neighborhood tree and greenspace to asthma emergency room visits: An application of advanced spatial data in Los Angeles County. International Journal of Environmental Research and Public Health, 18(7), 3487. doi:10.3390/ijerph18073487
Wolch, J. R., Byrne, J., & Newell, J. P. (2014). Urban green space, public health, and environmental justice: The challenge of making cities ‘just green enough’. Landscape and Urban Planning, 125, 234-244. doi:10.1016/j.landurbplan.2014.01.017
Yin, Y., He, L., Wennberg, P. O., & Frankenberg, C. (2023). Unequal exposure to heatwaves in Los Angeles: Impact of uneven green spaces. Science Advances, 9(17), eade8501. doi:10.1126/SCIADV.ADE8501
Zupancicm, T., Westmacott, C., Bulthuis, M. (2017). The impact of green space on heat and air pollution in urban communities: A meta-narrative systematic review. David Suzuki Foundation. Link
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