- We scrutinize major trends in remote sensing approaches for characterising UGSs.
- Number of studies focusing on mapping UGSs has increased rapidly.
- Most studies have focused on large areal extents rather than smaller patches.
- Few examples exist on change detection, biomass and carbon and vegetation health.
- There is a great need to develop more effective analytical approaches.
A knowledge of the characteristics of urban green spaces (UGSs) such as their abundance, spatial distribution and species composition, has an important role in a range of fields such as urban geography, urban planning and public health. Remote sensing technologies have made great contributions to the analysis of UGSs. However, a comprehensive review of the current status, challenges and potential in this area is lacking. In this paper, we scrutinize major trends in remote sensing approaches for characterising UGSs and evaluate the effectiveness of different remote sensing systems and analytical techniques. The results suggest that the number of studies focusing on mapping UGSs and classifying species within UGSs have increased rapidly over recent decades. However, there are fewer examples of non-tree species mapping, change detection, biomass and carbon mapping and vegetation health assessment within UGSs. Most studies have focused on UGSs (mainly trees) which cover large areal extents, with fewer studies of smaller patches such as street trees, urban gardens, recreational spaces and public parks, even though collectively such patches can cover substantial areas. Hence, we encourage future investigations to focus on a wider variety of different UGSs, particularly small-scale UGSs. We also recommend that research focuses on developing more effective image time series analysis techniques, methods to capture the complexity of UGSs and the use of SAR in studies of UGSs. At the same time, further research is needed to fully exploit remote sensing data within thematic applications such as monitoring changes in UGSs over time, quantifying biomass and carbon mapping and assessing vegetation health.