The impact of urban expansion and in-situ greenery on community-wide carbon emissions: Method development and insights from eleven US cities

Abstract:

Biogenic CO₂ emissions in cities are shaped by urban expansion and carbon sequestration from in-situ vegetation. To date, these two processes have not been studied together and compared with transboundary fossil fuel-based CO₂ emissions of urban energy systems. We leverage remote sensing and machine learning to quantify biogenic CO₂ emissions between 2006-2012, across eleven U.S. cities of varying climate, including central and suburban cities. Results find in-situ carbon sequestration by greenery varied moderately across cities (-2.1 to -0.87 Mg CO₂e ha^-1yr^-1) while emissions from carbon stock change due to land conversion varied much more (-3.4 to 9.8 Mg CO₂e ha^-1yr^-1), indicating that the latter dominates biogenic CO₂ emissions. As a ratio of community-wide energy use for travel and buildings, biogenic CO₂ emissions were a small proportion in core cities Denver (0.17%) and Minneapolis (0.33%) and as high as 38.2% in rapidly growing exurban communities. This research demonstrates that the GHG emissions impact of urban land cover changes can be quantified through machine learning techniques using publicly-available spatial data. This technique is replicable and can be used as a tool for cities seeking to include biogenic CO₂ emissions in their greenhouse gas accounting.