Neighbourhood affluence and environmental inequality

An investigation into the spatial distribution of trees within urban communities of Campos dos Goytacazes, Rio de Janeiro State, Brazil – of which some areas were highly affluent (1), some moderate to lowly affluent (2), and some very poor (3) – was undertaken during the early 2000s, and sought to assess whether there were environmental inequalities between the areas and, if so, what the causes and implications were.

Campos dos Goytacazes, established in 1835, was principally an area whose growth was fuelled by the sugarcane industry. On the surrounds of the settlement, sugarcane fields were therefore aplenty. However, during the early 1950s the industry went in to decline and much of these sugarcane fields were built on in the resulting period of rapid urban sprawl into the surrounding rurality. In fact, the authors note that this makes the city a good place for such a study, as the sugarcane fields were entirely cleared for construction – no trees existed before the construction took place. This allows for easy comparisons to be made between communities’ tree populations.

An overhead view of much of the city. Source: Skyscrapercity.

In order to draw comparisons, ten random communities were selected and then devided into the three categories aforementioned. Only one neighbourhood from the very poor category was sampled, because governments are not required to upkeep the area there as the residents do not pay taxes. Therefore, the government does not look after the tree population. From these communities, data in relation to tree populations were taken, and the results are shown in the table below.

Trees per square metre (Tree·m-2); trees per building (Tree·Bldg−1); private gardens per building (Garden·Bldg−1); land value (m2 value); and neighborhood age. Note that the poorest community is left out, likely as there were no trees.

From these results, the authors state that the number of trees present within a community is positively correlated with land value, whilst area age is not correlated with tree presence in any significant manner (meaning that just because an area has existed for a longer period of time it does not mean it will be more heavily populated with trees).

Additionally, tree diversity (and the number of trees from each tree species) in relation to the abundance of trees was also shown to be more even in more affluent areas, meaning that there is a more equally diverse yet plentiful tree population. These results are shown in the table below.

Shannon-Weaver Diversity Index (H) for the nine formal areas in Campos dos Goytacazes.

At this point the authors note that, contrary to past research, the age of an area plays little role in its tree population and species diversity. Instead, the level of affluency of an area is perhaps the significant determining factor. For example, in class 2 areas (moderate to low levels of affluency), 54% of the tree population comprised of the fast-growing Caesalpinia peltophoroides, whereas in class 1 areas the same species did not exceed 25% of the total tree population. In fact, in Parque Prazeres, which ranked lowest in the study, the species accounted for 70% of the tree population. However, it was always the most dominant species, regardless of its abundance. Other species within the city, many of which were also fast-growing (including Ficus benjamina and Licania tomentosa), indicates that fast-growng were preferenitally favoured – as, interestingly, were exotic species, which accounted for 40% of tree populations. Such data are supported by other studies from the wider region.

We can see how a poorer area exists in the foreground, with a slightly more affluent region behind. Source: Skyscrapercity.

In summary, it can be confidently stated that areas of high affluency in the city will benefit from diverse and abundant tree populations – in contrast to poorer areas. The authors remark that “the practical result is that wealthier neighborhoods that already have access to better public and private infrastructure also have an advantage in terms of the environmental amenities provided by trees”, which of course has a positive feedback loop for such affluent areas and much the opposite for poor areas. This is exacerbated by local government targeting its tree planting to rich areas, and ignoring the poorer communities. Until the local authorities recognise that their efforts are a causal factor behind the evident environmental inequality, there is little scope for change. More trees, or a wider variety of species, must be planted across the city, with no discrimination between areas based on level of affluence.

Caesalpinia peltophoroides within the urban environment. Source: Andre Benedito.

Perhaps this case study rings true of cities and towns in other countries across the world. Do arborists preferentially target affluent areas for planting, and select a richer array of species to plant in such areas, as they are more comfortable in planting the trees in such areas? Based on anecdotal evidence, I imagine so. Maybe it is because the level of risk with regards to tree survival is lower. Ultimately however, does the cause really matter, as long as environmental inequality exists? At least in Campos dos Goytacazes, there needs to be a drive to allow all areas to benefit from diverse and abundant tree populations, which would help remove environmental inequality and potentially act as a catalyst for further change.

Source: Pedlowski, M., da Silva, V., Adell, J., & Heynen, N. (2002) Urban forest and environmental inequality in Campos dos Goytacazes, Rio de Janeiro, Brazil. Urban Ecosystems. 6 (1-2). p9-20.

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