PNNL

Abstract

Abstract Human-Earth System Models (ESMs) and Integrated Assessment Models (IAMs) used to explore the land-atmosphere implications of future land-use transitions generally lack representation of urban areas or, if included, lack dynamic representation of urban lands. Here, we show that lack of incorporation of dynamic urban land processes can lead to global land budget imbalances and systemic implications to other ESM and IAM processes. We explore the integration of projected dynamic non-urban lands with projected dynamic urban lands from 2015 to 2100 at a fine resolution to examine the interactive stress and feedbacks to the land system, specifically compromised agricultural crop production and losses in carbon sequestration, that can arise from the competition over land resources. By 2100, future urban extensification could displace anywhere from 0.1 to 1.4 million km2 from agriculture lands, leading to 20 to 300 Mt (106 metric tons) of compromised staple crop (corn, rice, and wheat) production, a 1% to 13% reduction from 2010 levels. When considering increased production required for increasing populations by 2100, urban extensification could cut required increases in crop yields by almost half. Losses in net primary production (NPP) from displaced forest, grassland, and croplands ranged from 0.24 Gt (109 metric tons) C yr-1 to 2.24 Gt C yr-1, or anywhere from 0.3% to 4% losses in global NPP; however, this translates to an additional 1.19 Mt CO2 yr-1 to 6.56 Mt CO2 yr-1 (a 50% increase) in projected CO2 emissions.