Within cities, nature shape-shifts. In one urban enclave, native plant gardens may attract key pollinators. In another, vacant lots may draw invasive species. Grassy lawns may dominate some metro-area neighborhoods, while tree canopies overshade others.
What drives these patterns of urban biodiversity? In 2003, researchers dug into the question, focusing on the Phoenix area. They found that family wealth corresponded with greater plant diversity 鈥 a phenomenon they dubbed the 鈥.鈥 Since then, the concept has undergone extensive scrutiny over the past two decades, according to Renata Poulton Kamakura, who earned a Ph.D. from the Nicholas School of the Environment in May 2024.
鈥淭here鈥檚 been a huge focus in the urban ecology literature on the relationship between income and biodiversity, green spaces, ecosystem services and things like that,鈥 said Poulton Kamakura, who is now a science policy fellow in the .
Many studies show that the luxury effect , at least in the Global North. Less clear is why it occurs in some cases but not in others. Working with colleagues from North Carolina State University, Poulton Kamakura described a to identifying factors that shape patterns of urban biodiversity. The researchers published their work in November 2024 in the journal Ecosphere.
Here, Poulton Kamakura describes how biodiversity enhances cities, and how the team鈥檚 new research framework, called POSE, could ultimately help improve access to nature鈥檚 benefits.
A prairie in La Villita Park, which occupies a former polluted site, in Chicago. A grassroots effort led to site remediation and park development. Credit: Renata Poulton Kamakura
Biodiversity matters for a lot of things that both humans and non-humans need. For example, if you have a range of different kinds of trees in your city, then you have a much more resilient urban tree canopy that can provide things like shade and stormwater management. Also, biodiversity in cities supports conservation. Animals move through landscapes, including our cities. If we can create areas where humans and other beings can exist relatively well together, that鈥檚 a lot better for all of us.
There is a pervasive assumption that those with wealth prefer to have more biodiversity and have the means to support it. However, the evidence for that isn鈥檛 very robust. Some studies have found that people across incomes value biodiversity. Some have found that wealthier homeowners prefer manicured lawns that, partly due to pesticide and herbicide use, tend to have very low biodiversity. Although wealth can help homeowners achieve their landscaping goals, the relationship between wealth and biodiversity-related goals does not appear to be cut-and-dry.
We see the effect in a chunk of places, but we don鈥檛 see it in a lot of others, and we kind of go, well, that鈥檚 weird, but don鈥檛 really dive into why. If we can understand, mechanistically, why biodiversity is the way that it is in cities 鈥 what are the different policies, the different practices, the different actors at play here 鈥 then we can identify reasons why biodiversity inequalities exist and design interventions to address them.
The POSE framework is short for Power, Objectives, Sociological context and Effort. It pushes us to understand why certain patterns of urban biodiversity occur. First you identify one or a couple of 鈥渁ctors,鈥 like a city government or a homeowners鈥 association, who are making decisions that can impact biodiversity. Then you identify their power. How much money do they have to pay for things they want to do? Do they have contacts in powerful places? Do they have a lot of people they can mobilize to advocate on the issues that they care about? Then you think about objectives. What does the entity in power want to do? Maybe parking and driving is an issue, which could then have an impact on biodiversity.
The sociological context touches on ecology and social realms. Is the city really dry? Is it really wet? Are you in a place with a relatively autocratic government that gets things done quickly because they have an immense amount of power? Or are you in a place with more bureaucracy, where it takes a lot of time to get government to move?
Effort is how much the entity in power tries to achieve their objectives. You can have powerful entities that have potentially impactful objectives but simply do not try that hard, and change doesn鈥檛 necessarily happen. Or you may have grassroots organizations without much power who put in a lot of effort and get a lot done.
It鈥檚 meant to be partly for urban ecologists and social scientists of various kinds as they set up their study design. But it can also be for anyone 鈥 researchers or others 鈥 who is evaluating city programs or initiatives to see if they are achieving their biodiversity goals and, if not, perhaps get at why they aren鈥檛.
One of the big things is the amount of knowledge of social networks and social science that is necessary. The other challenge is going to be time. Trees, for example, take a long time to grow. So, to see the impact of a policy on tree canopy cover long-term, you ideally want to follow it for decades.
We want to see people build on POSE, adapt it, change it to their needs. And then hopefully the urban ecology community can continue to workshop it. My hope is to apply it in, ideally, drastically different contexts, and see if it is flexible or too complicated. We don鈥檛 claim to have all the answers, not by a long shot, but are instead trying to continue the conversation. There鈥檚 a lot of cool frameworks out there.
This Q&A is an edited version of a longer interview.
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