Mar. 2022 Science Corner | “The equity of urban forest ecosystem services and benefits in the Bronx, NY”

When most of us think of a forest, large urban areas like New York City are the last places that come to mind. Indeed, most of Blue Forest’s projects have been located in relatively remote landscapes, hours drive from major cities. However, urban areas can be home to large numbers of trees, which scientists and ecologists refer to as urban forests. “When we talk about urban forests, we’re talking about trees (and other plants) and the different configurations we find them in urban areas such as cities and towns,” says Dr. Charity Nyelele, a postdoctoral researcher at the University of California, Irvine. Like traditional forested landscapes, urban forests provide a host of important social, environmental, human health and economic benefits for communities living around them, but these services are often distributed unequally, with some groups benefiting more than others.

In a 2020 paper, Dr. Nyelele and her doctoral advisor, Professor Chuck Kroll, sought to identify how the ecosystem services and benefits from urban forests were distributed across communities in the Bronx, a borough of New York City.

“We wanted to understand what the distribution of the ecosystem services and benefits were across various socio-economic and socio-demographic divisions, who was getting more, and inform decision making on where we should focus tree planting in future to achieve equity and address issues of environmental injustice.”

The authors looked at air quality improvements, specifically PM2.5 air pollutant reductions; avoided stormwater runoff; carbon storage and sequestration; as well as air temperature and heat index reductions. They found that lower levels of these ecosystem services and associated monetary and human health benefits were generally associated with census block groups with lower socio-economic and socio-demographic markers.

“From this paper, we’re able to see that the distributions of trees as well as the ecosystem services and benefits they provide do support the inequity hypothesis, where you have census block groups that typically have higher poverty rates, higher population densities, lower income rates, and lower educational attainment being associated with lower tree cover and lower ecosystem services,” said Dr. Nyelele. That’s especially problematic, she points out, because “[these communities] tend to depend a lot on nature for survival as well as general human health and well-being. For example, chances are if you have a lower income, you don’t have the capacity to invest in air conditioning. Because trees have been shown to shade buildings and lower air temperature, you will benefit from this important service. We really need to think about equity and consider placing trees in communities that need them.”

Despite the well-documented benefits of urban forests, there can also be detrimental effects to indiscriminate tree planting, including gentrification, an increase in allergens, or trees being seen as providing cover for crime. To combat these negative outcomes, Dr. Nyelele emphasizes the need to engage the community in planning and decision-making processes before trees are put on the ground. “For this work, we were looking at the distributional equity, but going forward, there’s a need to understand some of those contextual and procedural issues: what does the community need, where do they need the trees, which species are they interested in and how can we make sure they’re involved in the decision-making process?”

“There are also issues of maintenance and stewardship. Putting the trees on the ground is one thing, but maintaining them so they survive and give those long-term benefits – there’s a lot of cost associated with that and the question of who’s going to manage it. So, when we involve the communities, you’re also engaging potential stewards for those trees.”

Like traditional forested landscapes, urban forests require investment to keep them healthy and maximize their benefits for people and ecosystems. Applying an equity lens can help prioritize projects and areas for investment and also improve the likelihood of positive outcomes by ensuring that communities are included in decision-making. As Blue Forest begins to explore projects in urban landscapes, research like Dr. Nyelele’s will be fundamental to guiding project development to ensure positive outcomes for all communities.