Spatial and Temporal Dynamics of  Carbon Sequestration in Stockholm  County's Green areas : A GIS-based Analysis

Abstract: The human influence of global climate is an issue currently assessed in various mitigation strategies. Stockholm County has committed to becoming carbon neutral by 2040 and negative by 2045 according to the Paris agreement. The strategy includes cutting of various sectors emissions as well as compensating for remaining emissions with carbon sequestration methods. Accounting for ecosystems ability to sequester carbon at local level in green urban areas is an important in carbon offset efforts. It has emerged from previous research that the sequestration rate may differ depending on vegetation age and thus time passing, which is not assessed on a regional level, which is important for carbon offset efforts to accurately account for the sequestration potential in long-term mitigation strategies. This study therefore aims to fill the knowledge gap of how the temporal aspect affects the current sequestration potential and future predictions, as well as assessing how it can aid in reaching carbon neutrality by 2040. The study are thus aiming to answer the research questions (1) how the carbon sequestration potential of the existing green areas change over time in Stockholm County, (2) if additional measures need to be taken to preserve or increase carbon sequestration to maintain carbon neutrality until 2040 and (3) how the knowledge of sequestration dynamics aid in reaching a carbon neutral city by 2040. A weighing of which Corine Land Cover categories was performed and concluded in the including; discontinuous structures, green urban areas, forests and wetlands, due to their contribution to sequestration potential, estimated change through time, and relevance for Stockholm County. The spatial analysis was made based on calculations with information obtained from processing of obtained data on land cover and species distribution as well as scientific literature on sequestration rates of each vegetation across all life stages, where Net Ecosystem Production was the main measurement used. The estimated results were computed in a Geographic Information System to simulate and visualize the sequestration rates of current and future predictions of 2040 sequestration potential as well as locating areas of interest. The findings show that by including temporal aspects to the assessment of carbon sequestration potential in Stockholm County, the current and future sequestration potential increased from previous research estimations. The total current sequestration potential was 2,8 MtCO2-eq annually and the predictions were estimated to 3,3 MtCO2-eq per year in 2040. As the current emissions in Stockholm County are currently 6 MtCO2-eq per year, the natural sequestration potential provided by the green areas is compensating for 46% of the current emissions. As the estimated future emissions are 0,95 MtCO2-eq annually, the natural sequestration potential more than compensates for the emissions in the county, if the predicted emission reductions are realized. Although further measurements are not seemingly required to achieve carbon neutrality in 2040, the findings further locate areas and species where management practices or protection is beneficial to further add to the sequestration potential of Stockholm County.