Net-Zero Target and Emissions from Land Conversions: A Case Study of Maryland's Climate Solutions Now Act

Many climate change "solution" plans include net-zero goals, which involve balancing the anthropogenic greenhouse gas emissions (GHG) with their removal. Achieving net-zero goals is particularly problematic for soils because they are often excluded from GHG inventories and reduction plans. For example, Maryland's Climate Solutions Now Act (Senate Bill 528) put forward the goal of lowering emissions of GHG to 60% under 2006 quantities by 2031 and with a target of net-zero emissions by 2045. To achieve these goals, the state of Maryland (MD) needs to quantify GHG emissions from various sources contributing to the state's total emissions footprint (EF). Soils are currently excluded from MD's GHG assessments, which raises a question about how the soil impacts the net-zero goal. This study examines the challenges in meeting net-zero goals using an example of carbon dioxide (CO2) as one of the GHG types (net-zero CO2 emissions). The current study quantified the "realized" social costs of CO2 (SC-CO2) emissions for MD from new land developments in the period from 2001 to 2016 which caused a complete loss of 2.2 x 10(9) kg of total soil carbon (TSC) resulting in $383.8M (where M = million, USD = US dollars). All MD's counties experienced land developments with various emissions and SC-CO2 monetary values. Most of the developments, TSC losses, and SC-CO2 occurred near the existing urban areas of Annapolis and Baltimore City. These emissions need to be accounted for in MD's GHG emissions reduction plans to achieve a net-zero target. Soils of MD are limited in recarbonization capacity because 64% of the state area is occupied by highly leached Ultisols. Soil recarbonization potential is further reduced by urbanization with Prince George's, Montgomery, and Frederick counties experiencing the highest increases in developed areas. In addition, projected sea-level rises will impact 17 of MD's 23 counties. These losses will generate additional social costs because of migration, costs of relocation, and damages to infrastructure. The state of MD has a high proportion of private land ownership (92.4%) and low proportion of public lands, which will limit opportunities for relocation within the state. Net-zero targets are important but meeting these targets without specific and integrative approaches depending on the source and type of emissions may result in failure. These approaches should also focus on the social costs of emissions, which raises the need for a new concept of integrating net-zero emissions and social costs.