Evaluation of the Value of Urban Composite Carbon Sinks:A Case Study of Shenyang

Objective In the context of urgent tasks to achieve dual carbon goals and establish an ecological compensation system, the evaluation of carbon sequestration value becomes particularly important. However, in current research on carbon sequestration ecological compensation, the value of urban carbon sinks is often overlooked. Therefore, this paper proposes a method for calculating the composite carbon sequestration value of urban areas based on the characteristics of urban ecosystems, aiming to reveal the composite carbon sequestration value of cities. MethodsUsing remote sensing imagery combined with plot data, we established a model for estimating carbon storage and calculated the natural and artificial carbon storage within the Shenyang Fourth Ring area from 2003 to 2023. We employed the afforestation cost method, carbon tax method, and carbon trading method to assess the composite carbon sequestration value of the study area. We analyzed the spatiotemporal variations in the composite carbon sequestration value using different methods, as well as the changing contributions of various carbon sequestration elements. Additionally, we conducted preliminary discussions on the relationships between different carbon pricing calculation methods, changes in carbon sequestration value, urban development, and compared urban spatial carbon sequestration values with those of other ecosystems. ResultsThe results indicate that from 2003 to 2023, the composite carbon sequestration value within the Shenyang Fourth Ring area, as calculated by the afforestation cost method, ranges from 599 million to 2.5 billion yuan, while the carbon tax method yields values ranging from 646 million to 864 million yuan, and the carbon trading method ranges from 623 million to 833 million yuan. There are significant differences in carbon sequestration value evaluations among different methods, suggesting that there is still room for the carbon trading price and carbon tax price in China to rise according to related research. Over the period of 2003-2023, the composite carbon sequestration value of the urban area has continuously increased. The values of vegetation and soil carbon sequestration exhibit a fluctuating trend, while the value of building carbon sequestration has consistently risen. The proportion of carbon sequestration value contributed by vegetation and soil has decreased from 43.61% and 46.15% in 2003 to 34.70% and 36.62%, respectively, whereas the proportion contributed by building carbon sequestration has increased from 10.24% to 28.70%. ConclusionThe important contribution of urban space to carbon sinks in terrestrial ecosystems should not be ignored, and the value of urban composite carbon sinks is slightly inferior to that of other terrestrial ecosystems such as forests in total volume, but it has a certain advantage in average annual growth; the evaluation of the value of urban composite carbon sinks can reveal urban spatial carbon assets, make clear the value of carbon sinks of the various types of carbon sinks in urban areas, and provide support for the further exploration of the impacts of changes in urban environments due to the conflict between natural and man-made spaces, The evaluation of urban composite carbon sink value can reveal the urban spatial carbon asset situation, clarify the current carbon sink value of various urban carbon sink elements, and then provide support for further exploring the influence of natural-artificial spatial conflicts and urban environmental changes on the value of carbon sinks, and provide new theories and methods for improving the efficiency of urban composite carbon sinks, as well as references for the decision-making and planning of land use that takes the comprehensive benefit as the main goal; the impact of various human activities on the value of urban composite carbon sinks is complex, and finding the key factors should be the focus of future research；in terms of the choice of different methods, the afforestation cost method is relatively unsuitable for evaluating the value of urban carbon sinks, but at the same time, there are also limitations of the carbon tax law and the carbon transaction law in the process of application. In the future, the regulation of carbon trading price and the formulation of carbon tax rate should refer to the afforestation cost of carbon sinks, so as to make it more adaptable to the evaluation of the value of urban composite carbon sinks.