Absence of a Luxury Effect on bird alpha diversity in a rapidly developing African city, but surrounding landscape is key

Aspiring towards cities that are sustainable and equitable, as detailed by Goal 11 of the United Nations Sustainable Development Goals, has become increasingly relevant given the growing human population in urban areas. A key part of guaranteeing that cities meet Goal 11 is to ensure equitable access to urban green spaces, and the biodiversity that they support, for all residents. However, there is evidence from developed world cities of a Luxury Effect, where wealthier residents have greater access to urban biodiversity than poorer residents. To test for this Luxury Effect in a developing world city, we measured bird species richness and diversity in 27 urban green spaces in Johannesburg, South Africa, to examine how socio-economic and ecological drivers influence urban biodiversity. We found no evidence of a Luxury Effect with the median income of neighbourhoods surrounding the green spaces having no significant effect on bird richness or diversity. There were, however, ecological effects with surrounding natural land-cover negatively correlated to richness, and a positive influence of wetland connectivity on richness. The negative effect of natural land-cover is possibly due to the relatively low bird diversity of the natural grasslands surrounding Johannesburg. The positive effect of wetland connectivity and the lack of a Luxury Effect indicate that the use of waterbodies to historically separate populations has buffered poorer neighbourhoods from depreciated biodiversity within the selected green spaces. The effect of wetlands also further emphasises the importance of water availability on urban biodiversity. This indicates that historical land use decisions can still influence how biodiversity is distributed in urban landscapes.

Automated summary

In Johannesburg, ecological factors have a significant impact on bird species richness, with natural land-cover negatively correlated and wetland connectivity positively influencing richness. The absence of a Luxury Effect suggests that historical use of waterbodies has played a role in buffering poorer neighborhoods from decreased biodiversity within green spaces. This study highlights the ongoing influence of historical land use decisions on urban biodiversity distribution.