Improving carbon sink capacity is critical for meeting energy conservation and emission reduction targets, along with low-carbon development goals. Although many researchers have recognized that urban space can significantly influence the capacity of carbon sinks in urban areas, few studies have quantified the impact of urban landscape patterns, particularly urban green space (UGS) morphology, on carbon sinks. This study quantitatively investigated the impact of UGS morphology on carbon sinks using panel data from nine cities in the Guangdong–Hong Kong–Macao Greater Bay Area (GBA), China, from 2000 to 2017. A series of landscape metrics and land-use data was first selected to quantify the four dimensions of UGS: scale, compactness, type diversity, and shape complexity. Subsequently, the impact of UGS morphology on carbon sinks was estimated using a panel data model. The main findings were as follows. (1) From the carbon sink results, the carbon sink in the GBA was found to be in an evolutionarily stable state, reflecting the relatively limited potential for carbon enhancement in the region. (2) From the landscape metrics results, the AREA_MD was mainly distributed between 0.18 and 0.27. The AI was mainly distributed between 80 and 97, with a concentration at 90. The PAFRAC was mainly distributed between 1.39 and 1.43, with a concentration at 1.41. PR was mainly distributed between 6 and 7. There was a large disparity in the scale of UGS morphology between GBA cities, with an irregular and complex pattern that became more compact over time. (3) From the panel data results, the AI (p < 0.001) had a significant positive impact on carbon sinks, while PR (p < 0.001) had a significant negative impact. The more compact the UGS morphology, the greater the total carbon sink, and the more complex the UGS morphology, the smaller the total carbon sink. The findings highlighted the importance of urban planning and UGS morphological optimization for increasing carbon sink capacity, as well as providing policy makers and urban planners with theoretical references and guidance for achieving climate goals.
