Racial, Ethnic, and Socioeconomic Disparities in Multiple Measures of Blue and Green Spaces in the United States

Background: Several studies have evaluated whether the distribution of natural environments differs between marginalized and privileged neighborhoods. However, most studies restricted their analyses to a single or handful of cities and used different natural environment measures. Objectives: We evaluated whether natural environments are inequitably distributed based on socioeconomic status (SES) and race/ethnicity in the contiguous United States. Methods: We obtained SES and race/ethnicity data (2015–2019) for all U.S. Census tracts. For each tract, we calculated the Normalized Different Vegetation Index (NDVI) for 2020, NatureScore (a proprietary measure of the quantity and quality of natural elements) for 2019, park cover for 2020, and blue space for 1984–2018. We used generalized additive models with adjustment for potential confounders and spatial autocorrelation to evaluate associations of SES and race/ethnicity with NDVI, NatureScore, park cover, and odds of containing blue space in all tracts (n=71,532) and in urban tracts (n=45,338). To compare effect estimates, we standardized NDVI, NatureScore, and park cover so that beta coefficients presented a percentage increase or decrease of the standard deviation (SD). Results: Tracts with higher SES had higher NDVI, NatureScore, park cover, and odds of containing blue space. For example, urban tracts in the highest median household income quintile had higher NDVI [44.8% of the SD (95% CI: 42.8, 46.8)] and park cover [16.2% of the SD (95% CI: 13.5, 19.0)] compared with urban tracts in the lowest median household income quintile. Across all tracts, a lower percentage of non-Hispanic White individuals and a higher percentage of Hispanic individuals were associated with lower NDVI and NatureScore. In urban tracts, we observed weak positive associations between percentage non-Hispanic Black and NDVI, NatureScore, and park cover; we did not find any clear associations for percentage Hispanics. Discussion: Multiple facets of the natural environment are inequitably distributed in the contiguous United States. https://doi.org/10.1289/EHP11164

. Descriptive statistics of NDVI (2020), NatureScore (2019), Park cover (2020), Blue space , and 2015-2019 SES and Race/ethnicity measures in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S2. Average 2015-2019 race/ethnicity composition by levels of NDVI (2019) in all census tracts (n =71,532) in the contiguous U.S. after excluding census tracts with missing data. Table S3. Average 2015-2019 race/ethnicity composition by levels of NatureScore (2020) in all census tracts (n =71,532) in the contiguous U.S. after excluding census tracts with missing data. Table S4. Average 2015-2019 race/ethnicity composition by levels of park cover (2020) in all census tracts (n =71,532) in the contiguous U.S. after excluding census tracts with missing data. Table S5. Average 2015-2019 race/ethnicity composition by levels of blue space  in all census tracts (n =71,532) in the contiguous U.S. after excluding census tracts with missing data. Table S6. Average 2015-2019 race/ethnicity composition by levels of NDVI (2019) in urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S7. Average 2015-2019 race/ethnicity composition by levels of NatureScore (2020) in urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S8. Average 2015-2019 race/ethnicity composition by levels of park cover (2020) in urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S9. Average 2015-2019 race/ethnicity composition by levels of blue space  in urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S10. Associations between 2015-2019 percent less than high school education, median household income, and percent below poverty level and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in fully adjusted models (Model 4), in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S11. Associations between 2015-2019 percent non-Hispanic White, percent non-Hispanic Black, percent Hispanic and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in fully adjusted models (Model 4), in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S12. Associations between 2015-2019 percent less than high school education, median household income, and percent below poverty level and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 1, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S13. Associations between 2015-2019 percent non-Hispanic White, percent non-Hispanic Black, percent Hispanic and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 1, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S14. Associations between 2015-2019 percent less than high school education, median household income, and percent below poverty level and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 2, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S15. Associations between 2015-2019 percent non-Hispanic White, percent non-Hispanic Black, percent Hispanic and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 2, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S16. Associations between 2015-2019 percent less than high school education, median household income, and percent below poverty level and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 3, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S17. Associations between 2015-2019 percent non-Hispanic White, percent non-Hispanic Black, percent Hispanic and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 3, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S18. Associations between 2015-2019 percent non-Hispanic Asian, percent non-Hispanic other and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in fully adjusted models (Model 4), in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S19. Associations between 2015-2019 percent less than high school education, median household income, and percent below poverty level and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 4 (fully adjusted) including a random effect by state, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S20. Associations between 2015-2019 percent non-Hispanic White, percent non-Hispanic Black, percent Hispanic and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 4 (fully adjusted) including a random effect by state, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S21. Associations between 2015-2019 median household income and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in fully adjusted models (Model 4) stratified by US census division, in urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S22. Associations between 2015-2019 percent non-Hispanic Black and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in fully adjusted models (Model 4) stratified by US census division, in urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Table S23. Associations between percent 2015-2019 percent Hispanic and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in fully adjusted models (Model 4) stratified by US census division, in urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Figure S1. The spatial variation of census tract level 2015-2019 % non-Hispanic Whites, % non-Hispanic Black, % Hispanic, Median household income, % <poverty level and % <high school education in the contiguous U.S. SES and race/ethnicity data are downloaded from the National Historical Geographic Information System (www.nhgis.org). Figure S2. The spatial variation of census tract level NDVI (2020), NatureScore (2019), park cover (2020) and blue space (1984-2018, +100m buffer) in the contiguous U.S. NDVI is based on Landsat 8 images, NatureScore is a proprietary measure created by NatureQuant, Park cover was based on the USGS Protected Areas Database of the U.S. (PAD-US), and blue space was based on the Joint Research Centre's Global Surface Water Dataset. Figure S3. The spearman correlation between NDVI (2020), NatureScore (2019), park cover (2020), blue space , population density, 2015-2019 race/ethnicity, 2015-2019 SES indicators in all census tracts (n =71,532) and in urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data. Figure S4. Associations of 2015-2019 median household income, and percent below poverty level and percent less than high school education with NDVI (2020), NatureScore (2019), park cover (2020) and blue space  in models with increasing adjustment for potential confounder in all census tracts (n =71,532) in the contiguous U.S. after excluding census tracts with missing data. See Table S2, S4, S6, S8 for corresponding numeric data. Figure S5. Associations of 2015-2019 median household income, and percent below poverty level and percent less than high school education with NDVI (2020), NatureScore (2019), park cover (2020) and blue space  in models with increasing adjustment for potential confounder in urban census tracts (n =45,338) in the contiguous U.S. after excluding census tracts with missing data. See Table S2, S4, S6, S8 for corresponding numeric data. Figure S6. Associations of 2015-2019 percent non-Hispanic White, percent non-Hispanic Black and percent Hispanic with NDVI (2020), NatureScore (2019), park cover (2020) and blue space  in models with increasing adjustment for potential confounder in all census tracts (n =71,532) in the contiguous U.S. after excluding census tracts with missing data. See Table S3, S5, S7, S9 for corresponding numeric data. Figure S7. Associations of 2015-2019 percent non-Hispanic White, percent non-Hispanic Black and percent Hispanic with NDVI (2020), NatureScore (2019), park cover (2020) and blue space  in models with increasing adjustment for potential confounder in urban census tracts (45,338) in the contiguous U.S. after excluding census tracts with missing data. See Table  S3, S5, S7, S9 for corresponding numeric data.         Table S10. Associations between 2015-2019 percent less than high school education, median household income, and percent below poverty level and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in fully adjusted models (Model 4), in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included percent less than high school education/median household income/percent below poverty level and were adjusted for median age, population density, temperature, precipitation, % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other, % Hispanic, latitude and longitude of the centroid.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other, % Hispanic and were adjusted for median age, population density, temperature, precipitation, median household income, latitude and longitude of the centroid.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included percent less than high school education/median household income/percent below poverty level and were adjusted for median age, and latitude and longitude of the centroid.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other, % Hispanic and were adjusted for median age, and latitude and longitude of the centroid.   Table S14. Associations between 2015-2019 percent less than high school education, median household income, and percent below poverty level and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 2, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included percent less than high school education/median household income/percent below poverty level and were adjusted for median age, population density, and latitude and longitude of the centroid.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other, % Hispanic and were adjusted for median age, population density, and latitude and longitude of the centroid.   Table S16. Associations between 2015-2019 percent less than high school education, median household income, and percent below poverty level and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 3, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included percent less than high school education/median household income/percent below poverty level and were adjusted for median age, population density, temperature, precipitation, and latitude and longitude of the centroid.   Table S17. Associations between 2015-2019 percent non-Hispanic White, percent non-Hispanic Black, percent Hispanic and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 3, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other, % Hispanic and were adjusted for median age, population density, temperature, precipitation, and latitude and longitude of the centroid.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic Other, % Hispanic and were adjusted for median age, population density, temperature, precipitation, median household income, latitude and longitude of the centroid.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included percent less than high school education/median household income/percent below poverty level and were adjusted for median age, population density, temperature, precipitation, % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other, % Hispanic, latitude and longitude of the centroid, and a random effect by state.
Note: For all census tracts, the following percentiles (20,40,60,80) Table S20. Associations between 2015-2019 percent non-Hispanic White, percent non-Hispanic Black, percent Hispanic and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in Model 4 (fully adjusted) including a random effect by state, in all census tracts (n =71,532) and urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other, % Hispanic and were adjusted for median age, population density, temperature, precipitation, median household income, latitude and longitude of the centroid, and a random effect by state.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included median household income and were adjusted for median age, population density, temperature, precipitation, % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other, % Hispanic, latitude and longitude of the centroid.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other, % Hispanic and were adjusted for median age, population density, temperature, precipitation, median household income, latitude and longitude of the centroid.  Table S23. Associations between percent 2015-2019 percent Hispanic and NDVI (2020), NatureScore (2019), Park cover (2020) and blue space  in fully adjusted models (Model 4) stratified by US census division, in urban census tracts (n = 45,338) in the contiguous U.S. after excluding census tracts with missing data.
Note: NDVI, NatureScore and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Models included % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other, % Hispanic and were adjusted for median age, population density, temperature, precipitation, median household income, latitude and longitude of the centroid.
Note: NDVI, Nature score and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Model 1 included education/household income/poverty and was adjusted for median age, latitude and longitude of the centroid. In Model 2 population density was added, in Model 3 annual average daily maximum temperature and annual average daily total precipitation were added, in Model 4 % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other, % Hispanic. Note: The following percentiles (20,40,60,80) are used to create Median household income ($) quintiles: 41135, 53214, 66468, 88640; % < poverty level quintiles: 5.5, 9.1, 13.7, 21.3; % < high school education quintiles: 4.4, 7.8, 12.1, 19.5. Figure S5. Associations of 2015-2019 median household income, and percent below poverty level and percent less than high school education with NDVI (2020), NatureScore (2019), park cover (2020) and blue space  in models with increasing adjustment for potential confounder in urban census tracts (n =45,338) in the contiguous U.S. after excluding census tracts with missing data. See Table S2, S4, S6, S8 for corresponding numeric data.
Note: NDVI, Nature score and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Model 1 included % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other and % Hispanic and was adjusted for median age, latitude and longitude of the centroid. In Model 2 population density was added, in Model 3 annual average daily maximum temperature and annual average daily total precipitation were added, in Model 4 median household income was added. Note: The following percentiles (20,40,60,80) are used to create % non-Hispanic White quintiles: 30.2, 60.4, 78.0, 89.9; % non-Hispanic Black quintiles: 0.6, 2.4, 6.8, 20.3; % Hispanic quintiles: 2.1, 5.2, 11.1, 27.0 Figure S7. Associations of 2015-2019 percent non-Hispanic White, percent non-Hispanic Black and percent Hispanic with NDVI (2020), NatureScore (2019), park cover (2020) and blue space  in models with increasing adjustment for potential confounder in urban census tracts (45,338) in the contiguous U.S. after excluding census tracts with missing data. See Table S3, S5, S7, S9 for corresponding numeric data.
Note: NDVI, Nature score and park cover were standardized and multiplied by 100, so that the beta represents the % increase/decrease of the SD (NDVI: 0.18, NatureScore: 33.4, Park cover: 0.13). Model 1 included % non-Hispanic White, % non-Hispanic Black, % non-Hispanic Asian, % non-Hispanic other and % Hispanic and was adjusted for median age, latitude and longitude of the centroid. In Model 2 population density was added, in Model 3 annual average daily maximum temperature and annual average daily total precipitation were added, in Model 4 median household income was added. Note: The following percentiles (20,40,60,80)