An assessment of the trees of the Greening Soweto Tree Planting Project in Johannesburg, South Africa

Abstract

The Greening Soweto Tree Planting project in the City of Johannesburg, South Africa, was a greening initiative aimed at ensuring that benefits of the 2010 FIFA World Cup, presented that year in the country, extended beyond the event. In assessing the trees of this project, it was confirmed that the target number of trees consisting mainly of indigenous tree species were planted predominantly as street and park trees in previously disadvantaged areas, traditionally known to have the least trees in the city. The survival rate of the project is estimated to be 43.46%, implying inadequacies in tree planting and management of the project and necessitating guidelines with recommendations to improve tree planting practices in the city. Growth relationship equations for Olea europaea subsp. africana and Searsia lancea were developed and the growth parameter analysis reveals that all trees grow better in parks but C. africana trees should rather be planted on sidewalks than on medians, S. lancea trees should preferably be planted on medians and C. erythrophyllum may be planted on sidewalks or medians as they would grow well in both locations. It is estimated that this project contributed 30 390.11 tCO2 of standing carbon stocks valued at R3 646 812,87 or US$303,901.07 (assuming a CO2 price of US$10.00) in 2017 and could potentially contribute 387 170.93 tCO2 of sequestered carbon stocks valued at R46 460 511,82 or US$3,871,709.32 by 2031 as mitigation action against climate change. A positive connection impacting the growth of the trees has been identified between land use, land cover and maintenance, indicating that the best locations for trees are maintained parks and formal residential areas as well as paved areas where irrigation is provided. The presence of pests and diseases, conflict with overhead structures and roads and a lack of pruning negatively impacted the growth of the trees. Guidelines for new tree planting projects have been developed with recommendations to maintain the canopy cover percentage in the established urban forest, enhance tree planting in the previously disadvantaged regions, improve the survival rate of new tree planting projects and establish community engagement forums to inform future tree planting of the city.