Trees as Infrastructure: Tracing the Historical Flow of Street Trees in London

Hannah Williams [Email] [LinkedIn]

This essay explores the intersection of infrastructure and environment through an anthropological analysis of street trees in London, addressing Alessandro Rippa’s concept of “environing infrastructure.” It critiques the conventional divide between green and grey infrastructure, examining how historical and socioeconomic contexts shape tree distribution and perpetuate inequality. Drawing on Dominic Boyer’s definition of infrastructure as reflective of Anthropocene concerns, the essay argues that street trees function as critical urban infrastructure, mitigating climate impacts such as urban heat islands and pollution. Using Phoenix, Arizona as a comparative case, it highlights how unequal tree coverage correlates with historic class and racial divides, emphasizing the urgency of studying London’s tree equity. A historical review reveals how London’s street trees originated in elite private spaces, reinforcing wealth-based environmental benefits. The essay concludes by advocating for a nuanced anthropological approach to urban green infrastructure that interrogates its role in both addressing and reproducing social inequities.

Introduction

While London is internationally recognised for its dense tree canopy and as a ‘forest,’ little has been written about the equity of dispersal of these trees throughout the city (Wood 2023, par. 2). In the past decade, scholars have noted the unequal dispersal of trees in urban settings and have argued that the imbalanced placement of trees often follows racial and socioeconomic segregation (Kallar N.D., par. 3). Moreover, there is a significant correlation between tree distribution and neighbourhood well-being, with areas lacking street trees experiencing higher temperatures, increased pollution, and greater vulnerability to climate change. (Phillips and Atchison 2018, 162). Neighbourhoods with fewer street trees are also more susceptible to these impacts as climate change worsens (157). On the other hand, street trees in cities have also been linked to mental well-being and increased physical health (Cameron 2022, 166-167). Streets trees can thus be seen as facilitators of well-being for a city, blending infrastructure with the environment with the benefits they provide. Because of this, the street trees of cities are increasingly being recognised as vital urban infrastructure.  

This essay answers Alessandro Rippa’s call for more “close [analyses] of infrastructure’s surroundings – the non-built, the environment, nature, and how these are continuously made and re-made” (Rippa 2023, 26). Rippa advocates for ‘environing infrastructure’ and defines this as “the bringing together [of] a processual understanding of the environment and of infrastructure as a historically situated intervention through which humans engage with and shape the planet” (27). Ultimately, Rippa argues that the delineation between ‘environment’ and ‘infrastructure’ is not as rigid as once thought; street trees in London provide an example of blurring the conceptual edges of what defines the ‘environment’ as street trees begin to be recognised as city infrastructure. In this essay, I follow Dominic Boyer’s definition of infrastructure as the “figuration of... concerns about life in the Anthropocene” (Boyer 2018, 226). Thus, a closer study of the street trees in London provides important insights into emerging anthropological considerations of the crossover between the environment and infrastructure.

Building on the segregated placement of urban street trees in the United States and Europe, I argue that a closer interrogation of the history and placement of street trees is needed in London (Fong 2021). Because of the international recognition of the segregation of street trees in metropolitan areas, further study on the street trees of London is not only warranted, but critical. Careful further study is needed to interrogate the status of street trees in London today, and this essay attempts to begin this conversation. I will first reflect on one of the most well-documented examples of tree inequity: Phoenix, Arizona, in the United States of America. The trees of Phoenix have received extensive coverage from both anthropologists and the media. While Phoenix significantly differs in climate from London, I intentionally chose to include this site for two reasons: (1) it is well-documented and (2) Phoenix inhabitants are experiencing the severe consequences of a lack of trees due to its desert climate exacerbated by climate change. The severity of the consequences possible from a lack of street trees in certain Phoenix neighbourhoods emphasises the urgency of interrogating the unequal placement of street trees in London. Moreover, because it is one of the most well-documented case studies on street trees, it will serve as a strong theoretical base on which to compare London street trees. From there, I will briefly reflect on the history of how street trees in London came to be, and will reflect on how the historical political system and class history of the UK impact current access to street trees. By situating the street trees of London in their historical, political, and global contexts, we will see how the environment and infrastructure are derivative of their contexts and replicate social inequality. I will conclude this essay with a reflection on this topic’s relevance to anthropological studies of the built environment today.

The (Restricted) Benefits of Trees

The benefits of trees in a city are many and are well-documented; they reduce air temperature, absorb air pollutants, prevent flooding, absorb noise, improve psychological health, increase property prices, and provide beauty (Cameron 2022, 166). In Trees in the City, Ira Nadel, Cornelia Oberlander, and Lesley Bohm reflect on the benefits of trees in a city, particularly for their provision of beauty, shade, protection, and comfort (Nadel, Oberlander, and Bohm 1977, 2). Moreover, they reflect on trees’ ability to provide “a sense of harmony and softness to the man- made environment of concrete and steel” (2). To scholars, popular media, and residents, trees are seen as an essential element to thrive in an urban landscape.

As noted in The Politics of Street Trees, street trees reduce urban heat island effects; the heat island effect is caused by the high density of concrete in cities that absorb and retain heat (Cameron 2022,166). Moreover, they can lower the cost of cooling buildings and lessen air pollution and can increase the physical and mental health of those living in and around denser collections of street trees (166). Because of these significant benefits, the Council of Europe’s Manual on Human Rights and the Environment conditions that “Every person has the right to live in an ecologically sound environment adequate for their health, well-being, dignity, culture and fulfillment” (Simson 2022, 190). Through their natural qualities and historic placement throughout cities, street trees have a specific capability of fulfilling these rights (190). However, the capabilities of street trees and green spaces to protect from the effects of climate change often remain undelivered.

Access to green spaces in London closely corresponds with the demographic and socioeconomic composition of each borough; more affluent neighbourhoods tend to have greater accessibility to green spaces (Kallar N.D., par. 6). Access to green spaces, including street trees, impacts the well-being of city residents. A 2018 participatory study found that communities with less access to green spaces are “less protected from income deprivation related health inequality,” and linked income inequality with green space inequity and life expectancy (Mitchell et al. 2018, 12; Kallar N.D., par. 3). The CPRE, a UK based conservation nonprofit, analysed the tree cover of neighbourhoods across the UK. They found that the “neighborhoods with the highest income levels... have more than double the tree cover per person than less affluent neighborhoods... and they have nearly 20% less of the toxic pollutant nitrogen dioxide” (CPRE 2023, par. 2). While this study was not specific to London neighbourhoods, they posited that the same was occurring throughout the UK. They specifically noted that the boroughs of Barking, Dagenham, and Hounslow have less tree cover than Richmond, which are less affluent neighbourhoods compared to Richmond and are thus experiencing fewer benefits from the trees (par. 3). Because of sparse tree cover, it is likely that these London neighbourhoods are experiencing higher heat levels in the summer and are exposed to more air pollutants. Recalling the definition of Boyer, infrastructure is a means of solving the problems of the Anthropocene (2018, 226). The street trees of London have become infrastructure as they are recognised by the city of London for their ability to address climate change; however, the hierarchical emergence of street trees continues to reinforce environmental disparity based on wealth today.

The State of Trees in Phoenix

Figure 2: A comparison between two neighborhoods in Phoenix, Arizona (D’Elia 2024).

Even though Phoenix and London differ in climate, they exhibit similar divides in access to the benefits of green spaces; access often follows the historical class segregation of neighbourhoods (Reardon and Bischoff 2011, 1093; Kallar N.D., par. 4). As a well-documented example of tree inequity, Phoenix will serve as a solid reference point on which to apply anthropological theory. This case study of Phoenix will be focused on the last decade and will primarily reflect on the current impact of street trees in Phoenix. Located in the American Southwest, Phoenix is the hottest city in America (Fong 2021, par. 1). In recent years, the heat natural for desert climates has reached a tipping point; the heat of the summer months has crept into early spring and late fall and often surpasses 115F (46C) for several weeks at a time (Lakhani 2023, par. 3). The effects of this have been felt throughout the entire region but have deadly consequences for vulnerable populations in the city, particularly unhoused people. The rising temperatures of Phoenix are exacerbated by the heat island effect; concrete and asphalt surfaces absorb heat and release it slower than natural spaces such as lawns, green spaces, and dirt (Lakhani 2023, par. 5). Because much of the city has dark roofs, asphalt roads, and concrete buildings and sidewalks, the heat of the day does not dissipate with the sunset, causing the heat island effect.

Trees can lower the temperatures of entire urban neighbourhoods because (1) the shade provided by their canopy prevents the concrete and asphalt below from absorbing and releasing heat and (2) their leaves create a cooler microclimate in their immediate surroundings through evaporation (Fong 2021, par. 2). Likewise, their shade can protect individuals from harsh, and sometimes deadly, sunrays (par. 2). An aerial view of the city reveals that the tree canopy is not equally felt throughout Phoenix. In the north and east (which are wealthier areas), there are many dense, green areas, while the south and west (which are mostly lower-income neighbourhoods) are almost completely brown (par. 3).

Thus, the benefits of street trees are in large part limited to the wealthier neighbourhoods of Phoenix. This mirrors larger trends of segregation in the United States. A study by Sean Reardon and Kendra Bischoff illustrates the history of how cities in America came to be largely segregated by household income and ethnicity (2011, 1093). The planning of street trees does not exist in a vacuum. Rather, they replicate the class attitudes and divides of neighbourhoods in which they are placed. More affluent areas have more dispensable income and can plant more trees on their private lawns; likewise, the city departments receive more funding from higher tax bracket areas and invest in green infrastructure at higher rates (Kallar N.D., par. 6). The city of Phoenix has recognised street trees as a valuable mitigation tool for extreme heat, or the problems of the Anthropocene, demonstrating how street trees have become a living infrastructure for cities (Boyer 2018, 226). However, unequal access to funding maintains a growing divide in access to this green infrastructure.

The explicit and known threat of heat in the desert makes it easy to forget that this danger remains outside of the desert. Phoenix is on the precipice of experiencing the deadly impacts of climate change and exemplifies the pertinence of adapting city infrastructure to prevent harm, exemplifying the blend of environment and infrastructure through its ‘green infrastructure’ plans. Non-desert metropolitan areas are also experiencing severe and fatal consequences from rising temperatures and pollution. Heat deaths and pollution-related harm have increased in the UK; according to the UKHSA, there were 2,803 excess deaths due to the heat wave of summer 2022 (Mayor of London 2022, par. 3). Extreme heat is expected to continue, and the Met Office “projects [a] greater chance of hotter, drier summers and warmer, wetter winters” (Met Office N.D., par. 1). While London may experience less extreme heat than Phoenix, the consequences of heatwaves in London are similar to Phoenix, with vulnerable populations experiencing the most severe effects. The role of street trees in London in reducing harm from heat has thus far remained unstudied. However, street trees have been recognised by cities, including Phoenix and London, as a solution for climate change mitigation. Both Phoenix and London use American Forest’s Tree Equity maps to view the tree density of the city based on race and poverty level (Bradshaw 2023, par. 18-19). The planting of street trees has emerged as a solution as older street trees are reimagined as a tool of protection against heat and pollution and to promote overall well-being. However, as seen in the example of Phoenix, these efforts to incorporate ‘green infrastructure’ replicate the same inequality due to insufficient funding. In London, the placement of street trees is closely related to the historic desires of the wealthy (Nadel, Oberlander, and Bohm 1977, 13).

The Historical Flow of a London Street Tree

The divide between ‘nature’ and ‘culture’ is not new and can be seen in modern anthropological conversations on the definition of and relationship between the environment and infrastructure. These debates echo Tim Ingold’s (2012) critique of the divide between material culture studies and environmental anthropology. In Toward an Ecology of Materials, Ingold (2012) argues that material culture specialists focus too heavily on “the artifactual domain” of life (427). Society is thus seen solely as a ‘human achievement’ facilitated through the utilisation of ‘objects and things,’ omitting “the entire gamut of organic life-forms... on which all life depends” (431). In anthropologists’ interpretation of and engagement with the material world, Ingold advocates for a consideration of “the material flows and formative processes wherein [an object or thing] [comes] into being” (431). I aim to situate street trees in their flows and processes of being by considering the historical context from which they emerged.

London is now known, marketed, and internationally recognised as a ‘forest’. This comes from the UN definition as an area of land with at least 20 percent tree coverage; London stands at 21 percent tree coverage (Wood 2023, par. 2). The history of the city’s trees comes from the ancient woodlands that surrounded medieval London, the land around estates, private gardens, squares, and eventually street trees (par. 2). Street trees were initially confined to the private gardens and affluent neighbourhoods of London (Nadel, Oberlander, and Bohm 1977, 13). An analysis of the historical decisions and processes of placing street trees underscores how past decisions continue to influence contemporary tree distribution patterns, which still perpetuate environmental injustice.

A reflection on the history of street trees globally and locally in London reveals the hierarchy entrenched in the development of the modern street tree. Nadel, Oberlander, and Bohm (1977) trace the lineage of street trees from trees planted for shade along the Nile River basin to the more recent developments of urban trees in continental Europe in the 17th century (11). Street trees in London developed from the landscaping plans of wealthy or palatial private gardens, which were used to lend “order and dignity” (13). The landscape planting of trees in Europe began in the 17th century and was often done in government, royal, or wealthy private gardens (13). These trees represented the “degree of civilization in a country;” the more landscape trees a country had in visible sites, the greater their authority (11). These trees were isolated on the outskirts of cities or in rural areas. Even as trees started to be planted along streets, they were not a part of the public landscape. They lined squares, gardens, and parks, and remained “separated from the activities of the metropolis” and its lower- and middle-class publics (14). These green spaces were predominantly private, isolating trees from the public sphere of the city. Beginning in the 17th century, “the square [dominated] the geography of London” and marks an important evolution in the street trees of London (15). The square emerged as a solution for wealthy urban residents to connect with nature (15). With the square, wealthy urban residents could access private green spaces while still being “separated from the main thoroughfares and commercial districts” (15). Like the example of Phoenix, we can see that street trees emerged from a history of restricting green spaces and their benefits to the wealthy.

Even as street trees began to emerge in London, they were not always viewed as compatible or synonymous with infrastructure. Jan Woudstra and Camilla Allen connect the shift in tree placement to wider values and attitudes toward ‘nature’ at the time. Attitudes shifted from ‘biophobic’ (viewing trees as something that damages infrastructure) to ‘biocentric’ (trees became infrastructure) (2022,165). However, these urban trees continued to only benefit a select few. The street trees now familiar to the residents and visitors of London began in the late 19th century. In 1862, plans were made to construct a new Embankment on the Thames; as the sewage system and underground railways were developed, plans for gardens and boulevards also emerged (Woudstra and Allen 2022, 153). Trees were planted alongside the boulevard for the first time in London (153). Even though trees began to be planted in public areas, the majority of tree cover was focused in older neighbourhoods in private gardens and streets (Cameron 2022, 165). The majority of working-class families in London did not have a front garden, so the paved streets in these areas remained treeless and bare (Johnston 2017, 6). Thus, an analysis of the history of how trees came to be in London reveals how current tree inequity manifests. The division of access to the benefits of trees continues to replicate class divides in the United Kingdom. More affluent areas have more historic trees and are thus further shielded (at least in part) from rising temperatures due to climate change and air pollution.

Trees as Infrastructure

London's street trees serve as both a reflection and perpetuation of socioeconomic inequalities. An exploration of the global and historical contextual flows that constitute the modern London street trees is relevant to contemporary anthropological interpretations of the built environment. By recognising street trees as infrastructure, I challenge the conventional divide between material culture studies and environmental anthropology, as critiqued by Ingold (2012). However, I diverge from the institutional engagement with trees as infrastructure and acknowledge that solely recognising trees as infrastructure is insufficient. A closer anthropological critique of ‘infrastructure,’ ‘green infrastructure,’ and the ‘environment’ is required to provide an avenue of critique of harm caused through green infrastructure.

The urban forest is part of a larger infrastructural system that provides “environmental, economic, social and health services” in cities (Wolf et al. 2020, 1). Social scientists and environmental scientists have been debating how to describe the role of the environment in infrastructure; to some, the urban forest is comprised of trees in parks, private gardens, and street trees and is part of a larger ‘green infrastructure system’ or ‘urban ecological infrastructure’ (Wolf et al. 2020, 2; Li et al. 2017, S12). The infrastructure of a city impacts and creates the urban ecosystem, one which is comprised of built structures, humans, and the more-than-human world. Traditionally, infrastructure is thought of as “roads and highways, electrical grids, and systems... [of] water” (Li et al. 2017, S12). However, infrastructure is “the basic physical and organizational structures that society requires for its operations,” which as previously established, includes the trees of cities (Li et al. 2017, S12). This viewpoint is still insufficient because it maintains a divide between the environment and built infrastructure and only considers the agency of humans and their built objects. This replicates the human exceptionalism Ingold (2012) is critiquing. Humans, their built environments, and the environment interact, converge, and function as one ecosystem. The epistemological divide between green and grey infrastructure causes “less attention [to be] paid to the relations between the built and the non-built” (Rippa 2023, 26). The example of street trees provides an example of how the inequality experienced by vulnerable populations is enshrined in grey and green infrastructure.

As cities expand and change over time, “different infrastructures are built to address the increasing human demands” (Li et al. 2017, S12 - S13). The expansion of urban surfaces such as concrete and asphalt raises questions about the health impacts this has on human life (S12). Concrete and asphalt contribute to the heat island effect; the heat island effect, flooding, and air pollution reveal the “weakness of... traditional grey infrastructure and its inability to cope with... climate change” (Li et al. 2017, S12). As cities seek to adapt to climate change, they are increasingly turning to more adaptable solutions, especially ‘green’ infrastructure, such as “urban forests, parks, woodlands, green roofs, wetlands, rivers, and other natural spaces” (S12). The term green infrastructure was developed to refer to the “combined structure, position, connectivity, and types of green spaces which together enable the delivery of multiple benefits as goods and services” (S13). This is a step forward as it recognises the important role of green spaces in cities. However, it upholds a division between the green and grey infrastructure of cities and poses green infrastructure as an unproblematic solution to the failures of grey infrastructure. This in turn ignores the history of the development of green infrastructure in a city and ignores how green infrastructure has caused harm by reproducing social inequality.

Alessandro Rippa critiques the dichotomy between green and grey infrastructure, advocating for recognition of the agency of the environment as it impacts both ‘traditional’ infrastructure and city inhabitants (2023, 25). This perspective emphasises the co-creation of a city's ecosystem by human and non-human actors, as well as the relationship between green and grey infrastructure. From this viewpoint, the ecosystem of a city (that in turn impacts human health) is co-created by the human and non-human worlds and by green and grey infrastructure. There is a close relationship between “landscapes and human-made infrastructure – the landscape itself being the result of specific human interventions” (Rippa 2023, 30). Rather than sloppily merge ‘green’ and ‘grey’ infrastructure, Rippa analyses the “interactions between humans and their environment” and takes note of how these interactions are mediated by infrastructure and influenced by larger structures of power and inequality (30). From this perspective, interaction with street trees and their benefits is dependent on your neighbourhood. In less affluent areas, this interaction is often limited due to the previously established sparse density of trees. This framework acknowledges the complicity of green infrastructure in reproducing social divides, while still providing space for untangling the relationship between ‘infrastructure’ and ‘environment.’

Conclusion

Shaped by centuries of urban development, London's street trees reflect patterns of socioeconomic inequality and often recreate environmental injustice. The disparity in tree distribution across neighbourhoods reflects historical class divisions, with affluent areas enjoying greater access to the benefits of green infrastructure. As London attempts to undertake climate change mitigation efforts, the role of street trees becomes increasingly critical. They not only mitigate the heat island effect and air pollution but also promote mental and physical well-being. Street trees’ potential to mitigate climate risks remains unrealised in many neighbourhoods in London, illustrating how street trees are an essential component of city infrastructure as cities adapt to a changing environment. As anthropologists seek to understand the inequitable realities enshrined in infrastructure, the case study of street trees illustrates the importance of including more-than-human worlds in future anthropological studies of the built environment. Embedded within the historical legacy of London’s urban landscape, street trees are active participants in the environmental and economic disparities that continue to shape the city. Further consideration is needed on the agency of trees in their role as city infrastructure. Such exploration will continue to develop the ideas presented in this paper and will help bring more complex and intricate understandings of the relationships between constructed sites, people, and plants. Through these endeavors, we will become more aware of our urban landscapes as co- constructed by humans, inorganic non-humans, and organic life.

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