Spatial and Temporal Shifts and Driving Mechanisms of Embodied Carbon in Water Transport Trade in BRICS Countries

From an ecological protection perspective, clarifying the spatial and temporal transfer characteristics of embodied carbon in water transport trade among BRICS countries and its driving mechanisms is of great significance for the precise formulation of emission reduction policies. This study integrates the multi-regional input–output model with the LMDI decomposition method to quantitatively analyze the bi-directional flow of embodied carbon in water transport trade among BRICS countries from 1995 to 2018, along with its spatio-temporal differentiation patterns. The driving mechanisms are decomposed across three dimensions: scale, structure, and intensity. By adopting a dual perspective of time-series and spatial correlation, the study systematically uncovers the cross-regional transfer patterns of embodied carbon emissions in water transport trade and examines the interaction pathways of various effects throughout their dynamic evolution. The study finds that (1) the embodied carbon in water transport trade among BRICS countries shows a trend of transnational transfer, with China being the largest net exporter (35.15 Mt in 2018), India and South Africa as net importers (−32.00 Mt and −1.89 Mt in 2018, respectively), and Brazil and Russia shifting from net importers to net exporters; (2) from a temporal perspective, the scale effect drives the growth of embodied carbon emissions (contribution values: 1.23~119.72 Mt for export trade; 4.88~34.36 Mt for import trade), while the intensity effect has a suppressive role (contribution values: −59.08~−1.48 Mt for export trade; −20.56~−5.31 Mt for import trade), and the structural effect is complex in its impact on emissions (contribution values: −17.72~0.45 Mt for export trade; −6.84~13.93 Mt for import trade). Optimizing the trade structure can help reduce carbon emissions; (3) from a spatial perspective, carbon emissions are higher in Southeast Asia and the Northern Hemisphere, and changes in China’s carbon emissions (total effect in 2018: 57.01 Mt in export trade and 7.98 Mt in import trade) significantly affect other BRICS countries. Based on the conclusions of the study, it is suggested that BRICS countries should strengthen cooperation to achieve regional emission reduction targets by optimizing the trade structure of water transport, promoting energy structure reforms, advancing green transport technologies and equipment, and establishing a carbon emission regulatory system.