Decarbonization strategies for North American urban landscapes: Evaluating pavements and vegetation across design typologies

Abstract

Urban landscapes are increasingly recognized as critical to climate mitigation, yet remain underrepresented in carbon accounting frameworks relative to buildings and infrastructure. This thesis advances landscape carbon assessment by introducing a typology-based Life Cycle Assessment (LCA) framework for landscape architecture. The framework integrates anthropogenic emissions and natural carbon dynamics while addressing uncertainty. It proceeds through three layers of analysis: 1) developing landscape system and project categories for carbon footprint benchmarking, 2) benchmarking the performance of the proposed landscape systems and urban typologies; and 3) assessing the mitigation potential of decarbonization strategies across systems and project types. Concrete pavers on reinforced concrete slabs and asphalt pavements (78 to 104 kgCO₂e/m²) are the most carbon intensive in the production-to-construction stage. Turfgrass and shrubs show wide variability, functioning as sources or sinks depending on species mix, maintenance, and flux magnitudes, underscoring the need for species-specific, ecologically dynamic modeling (-21 to 42 kgCO₂e/m² and -35 to 258 kgCO₂e/m²). Canopy systems act as consistent carbon sinks (-611 to -388 kgCO₂e/m² over 50 years) despite significant emissions from transportation and structural soil. Landscape systems were used to benchmark four urban typologies—streetscapes, plazas, courtyards, and urban parks. Their 50-year carbon footprints range from –80 to 21 kgCO₂e/m² in urban parks, –13 to 63 in courtyards, 22 to 79 in plazas, and 3 to 80 in streetscapes. Applying decarbonization strategies makes all typologies achieve net carbon sink status at the high bound. Urban parks achieve neutrality immediately post-construction, courtyards in 13 years, plazas in 26 years, and streetscapes by year 33. At higher emission estimates, urban parks and courtyards deepen carbon sink performance, plazas cross into net sink territory, and streetscapes approach neutrality. The detailed findings highlight the influence of planting density, maintenance regimes, and land cover composition. By structuring assessment around land covers and urban typologies, this thesis delivers a transferable carbon accounting framework aligned with design practice, offering actionable insights for embedding climate accountability into landscape architecture and public policy.