Dominic Henry, Ecological Modelling Specialist, EWT Conservation Science Unit (CSU)

Reference: Chamberlain, D.E., Reynolds, C., Amar, A., Henry, D.A.W., Caprio, E. & Batáry. 2020. Wealth, water and wildlife: landscape aridity intensifies the urban Luxury Effect. Global Ecology & Biogeography.

Biodiversity plays an important role in urban ecosystems and restricted access to it can profoundly affect human wellbeing. Unfortunately, urban dwellers rarely have equal access to biodiversity. Ecologists studying urban ecosystems have in many cases revealed a pattern whereby wealthier neighbourhoods in many cities have higher levels of biodiversity than poorer areas – a phenomenon that scientists have called the “Luxury Effect”. The Luxury Effect is indicative of environmental injustice, as the benefits associated with biodiversity are not shared equitably across society.

A new study published in Global Ecology & Biogeography by an international team of scientists from the University of Turin in  Italy, the University of Cape Town and the University of Witwatersrand in South Africa, and the Centre for Ecological Research in Hungary, and co-authored by EWT staff member Dominic Henry, conducted a meta-analysis (an analysis that combines the results of multiple scientific studies) to determine the generality of the Luxury Effect and identify factors that drive variation in this pattern. The authors tested the Luxury Effect across 96 studies from around the world that examined the relationship between socioeconomic status and biodiversity.

The authors found that there was a significant positive relationship between terrestrial biodiversity (including the abundance and species richness of plants, birds, reptiles and insects) and the level of wealth in a city, confirming the existence of a global luxury effect. An interesting finding was that this relationship was far more prominent in the drier regions of the world suggesting that the Luxury Effect could partly be driven by water availability. Wealthier people living in more arid regions may invest more in water features, such as ponds or swimming pools, or in irrigation of their gardens and parks. Alternatively, wealthier areas may be associated with wetter areas within these arid landscapes, with higher property prices associated with lakes, rivers, or other wetland features.

The relevance of this finding in a South African context is profound given how city planning under the apartheid government fell along racial lines. Within cities, most black South Africans continue to live on the periphery in areas where the land is degraded, and often within close proximity to industrial sites where access to clean air and water are limited. Understanding the finer details of the mechanisms that drive and maintain the Luxury Effect can help with the creation of more equitable cities in the future. Acknowledging that access to biodiversity is an incredibly important part of our lives can help facilitate the management of urban areas to make access to the benefits of biodiversity more equal across the socioeconomic spectrum.

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