Uniting geospatial assessment of neighborhood urban tree canopy with plan and ordinance evaluation for environmental justice

Abstract

Trees are not evenly distributed across urbanized areas and there is evidence that Black, Hispanic, and low-income residents have lower proximal tree canopy coverage. The complex interplay between social policy and the built/physical environment contributes to these outcomes, but much of the research on environmental justice focuses on either producing evidence of inequity or assessing policy to determine its effect on the physical environment. This paper attempts to unite those two approaches by 1) measuring the urban tree canopy (UTC) at a scale that reflects local socio-political decision making and 2) assessing how the local policy documents regulating UTC acknowledge and attempt to remediate disparity. A maximum likelihood supervised classification of 1-m resolution imagery for a purposive sample of twelve historically racially segregated neighborhoods in two North Carolina cities estimated UTC at the block level. Using a spatial autoregressive model, we found a statistically significant negative association between UTC coverage, percentage of non-White population, the presence of nonresidential zoning, and percentage of parcel within the right-of-way. Content analysis found the municipal comprehensive plans and development management ordinances lack city-wide canopy coverage goals, do not utilize neighborhood geographies to target action and evaluation, and do not account for, or attempt to reduce, the potential inequitable distribution of urban trees. Existing policies could further contribute to disparate UTC outcomes by allowing neighborhoods to create their own UTC coverage standards and by crafting ordinances with variable standards for neighborhoods with non-residential zones. As a result, communities unable to counteract intensive zoning and/or advocate for enhanced tree canopy provisions are at a disadvantage in the remediation of UTC disparities. These findings highlight the need for analytical approaches that integrate the identification of disparities with the evaluation of present-day policy frameworks that may perpetuate and/or exacerbate inequitable outcomes.