Urban forest inequity

Urban forest inequity, also known as shade inequity or tree canopy inequity, is the inequitable distribution of trees, with their associated benefits, across metropolitan areas. This phenomenon has a number of follow-on effects, including but not limited to measurable impacts on faunal biodiversity and the urban heat island effect. Urban heat inequity occurs when intra-urban heat islands, with their associated negative physical and emotional health consequences, are more common and more intense in lower-income communities.
Potential solutions to urban forest inequity include but are not limited to investment in marginalized communities, tree-planting initiatives, and more. Examples of urban forest inequity can be seen in various cities across the world.
Urban forests are areas of land covered by trees or other vegetation located in and around places of intensive human influence, particularly metropolitan, urban areas such as cities. Urban forests, though present on both public and private land, typically are found on public spaces due to the predominance of street trees noted by researcher Steven Strom. Urban forests are recognized for their significant role in mitigating the impacts of climate change, exemplified by their role in mitigating heat and flood risks and their contribution to green infrastructure is seen as a nature-based solution for climate change adaptation and mitigation. Trees and vegetation absorb and store rainwater during heavy rainfall events, reducing flood risk, and capture carbon dioxide from the atmosphere as part of climate change mitigation efforts. Additionally, urban forests are also important in maintaining the biodiversity of an urban area, particularly the avifauna (birds) of the area. These characteristics of urban forests help contribute to the creation of healthy, resilient, and sustainable cities in a cost-effective manner.
Urban forest inequity is a phenomenon in which the distribution of and access to trees and nature is inequitable in urban areas. It is thought to be an example of environmental injustice, as it disproportionately impacts marginalized communities. Numerous studies, including a 2017 meta-analysis done by researchers Ed Gerrish and Shannon Lea Watkins, have found a positive relationship between income and urban forest coverage. This introduces the concept of the luxury effects, which explains how the disparities in urban forest cover coincide with socio-economic and historical factors. The luxury effect illustrates how wealthier areas tend to exhibit higher biodiversity, reflecting the influence of socioeconomic factors and education levels in shaping the quantity and quality of green spaces in a given area. Moreover, inequitable distribution of greenery in urban areas may restrict an equal distribution of the benefits of urban forests, which include reducing stress and anxiety, cultivating a safe community, emotional fulfillment, mitigating the effects of global warming, and more. For instance, canopy cover quantity in an area can diminish the urban heat island effect and increase carbon sequestration from the atmosphere. Various historical, cultural, and institutional factors contribute to the perceived inequities in urban forestry management and inequitable distribution of urban greenery. A 2022 paper published in the International Journal of Environmental Research and Public Health found that vulnerable residents of an urban area, particularly lower-income residents and those who live further from urban forests and green space, are particularly susceptible to the urban heat island effect. There are examples of urban forest inequity in cities globally, some of which are listed below.
Environmental justice and spatial justice are two ideologies associated with the problems presented by urban forest inequity, and these ideologies seek to understand the disproportionate quality of life due to uneven environmental or spatial conditions and benefits. Problems commonly associated with urban forest inequity include but are not limited to the urban heat island effect, public health concerns, and the inequitable distribution of environmental benefits. In a 2022 paper, socio-spatial inequalities specialist Bernard Bret and geographer Sophie Moreau described environmental justice and spatial justice as two concepts defined by an interconnectedness between geographical space and quality of life. The U.S. Environmental Protection Agency has found that inequities are most often visible along the lines of “income, race, color, or national origin.” For example, South Africa historically has treated minority populations unequally, particularly by means of racial segregation, perhaps most clearly evident in the South African apartheid that occurred for the greater part of the twentieth century. Researchers in South Africa in a 2018 report found correlations between an increased risk of cancer and chemical poisoning, as well as of respiratory diseases like asthma, are of a much greater likelihood in marginalized communities that are negatively affected by environmental and spatial injustice, because individuals there may be more often be at risk of exposure to dangerous pollutants in water or in the air.
The U.S. E.P.A. defines the urban heat island effect as a phenomenon where urban areas experience higher temperatures than surrounding areas. Air temperature inside urban areas can be about 1–3°C or 1–7°F higher than rural or surrounding air temperatures, on average. This is due to a variety of reasons, which include but are not limited to lower albedo on urban surfaces, anthropogenic heat released from buildings and vehicles, and reduced areas of evapotranspiration. Asphalt and concrete, surfaces that are more common in urban areas, have a higher albedo than surfaces such as trees, grass, or snow. In addition, evapotranspiration is a powerful cooling process, and the relatively reduced amount of greenery in urban areas compared to rural areas contributes to the urban heat island effect. Without urban forests, the cooling mechanisms of high albedo and evapotranspiration do not work to cool the geographic area. Additionally, the E.P.A. has found that lower-income communities and those of color are particularly susceptible to the phenomenon known as intra-urban heat islands, which is due, in part, to historical redlining. As urban forests help combat urban heat islands and intra-urban heat islands, redlining contributes to this instance of environmental injustice.
Some cities have historically faced problems concerning urban forest inequity. They may have a disproportionate amount of green space in higher-income communities or face criticism from those who advocate for environmental justice. Beijing, China is one of those examples, demonstrated by the lack of accessibility to green spaces compared to gated communities. Research was published in the journal Environment and Planning B: Urban and City Analytics with data from the Beijing Green Spaces System Planning which found that higher-income gated communities had more access to green spaces than lower-income residential communities and that the urban planning was not meeting the demand for public parks and playgrounds in the densely populated regions of the city.
New York City is another example of a city that has historically faced challenges with urban forest inequity. Because of the urban heat island effect, concrete in the city draws more heat and raises temperatures, so more shade coverage is needed to protect inhabitants. A 2023 editorial written for the New York Daily News found that many neighborhoods in the city lack shade protection and may subsequently face temperatures “20 to 45 degrees hotter than those with more shade,” and these are typically lower-income communities. Moreover, researchers have often cited Chicago as another U.S. city facing difficulties in mitigating urban forest inequity. The city is actively trying to combat the lack of greenery and pollution they are facing through planting trees across different neighborhoods.
In 2021, a paper published in the International Journal of Environmental Research and Public Health worked to identify which regions in Delhi, India were experiencing high levels of urban heat, and consequently if they had sufficient green space or areas with urban forestry of some kind. According to the researchers, the results “documented how the spatial distribution of heat and greenspace relates to the spatial distribution of social vulnerability at the ward level in Delhi.” Rafael Fernandez-Alvarez of Arizona State University conducted similar research on Mexico City, Mexico pertaining to the distribution of green public spaces for inhabitants. The researchers found that these spaces are often biased against marginalized populations. The evidence showed that they mostly exist in the wealthy areas of the capital city, while the more populated lower-income communities lacked green public spaces.
Efforts to address urban forest inequity must effectively combat both environmental and spatial injustice in addition to urban heat islands. Some argue this may include activists and policymakers engaging directly with marginalized communities, public investment in underserved neighborhoods, and tighter government restrictions regarding land use and pollution concerns. A 2023 article published in the National League of Cities offered several potential solutions to combat urban heat islands, which included but are not limited to: increasing green space by planting trees along streets or sidewalks, converting existing roof spaces to green roofs, replacing normal pavement with sustainable alternatives, subsidies for planting trees, and active engagement of low-income communities, among others.
Furthermore, a potential solution to address this issue is the implementation of tree-planting initiatives. These initiatives aim to provide resources and support to historically underserved areas, thereby contributing to a more equitable urban environment. However, it is important to recognize that simply planting trees in low canopy-covered areas may not be sufficient to combat this environmental inequity. Initiatives must adhere to specific practices aligned with urban forest management objectives to ensure the creation of an equitable urban environment.
Moreover, it is important to consider the potential impacts of tree-planting initiatives before their implementation, as they may unintentionally contribute to environmental gentrification. Studies have shown that within a 10-meter buffer of the newly planted street trees, properties tend to experience a notable increase in value, indicating a positive correlation between planting street trees and property values. However, it is worth noting that the rise in property values may not always translate to benefits for underserved communities. To counter eco-gentrification, there are some key practices for tree-planting initiatives to follow, which are described by Sousa-Silva et al. (2023) and Haffner (2015), including integrating initiatives with long-term management strategies, creating community engagement, and introducing changes gradually.
An example of a tree-planting initiative that is currently ongoing is the Million Tree Initiative. New York City is an example of a city who implemented this initiative in recent years. The city launched the MillionTreesNYC initiative in 2007, which is now recognized as one of the largest and greatest-funded tree-planting initiatives in the United States. This initiative was a collaboration between the New York City Parks Department and the NY Restoration Project (NYPR), resulting in the successful planting of one million trees across five boroughs of New York City in less than a decade. Guided by considerations of health and socioeconomic factors, the initiative targeted neighbourhoods with the greatest lack of trees, aiming to improve urban canopy coverage by 20%. NYPR, a local non-profit organization, actively engaged the community in the planting and maintenance of the newly planted trees. This initiative was supported by collaborations with external partners and had help from volunteers around the city. After the initiative successfully planted one million trees across five boroughs, plans were made to update the street tree census and offer a user-friendly public map of trees to increase community involvement and create a culture of tree stewardship. MillionTreesNYC serves as a notable example of effectively increasing canopy cover in historically underserved areas, inspiring similar efforts in other cities, including Los Angeles.