by Rick Pruetz, Vice President, Ecocity Builders
The environmental impact of future growth can be cut in half by the formation of compact cities where dense, mixed-use development increases the energy efficiency of buildings, transportation and other infrastructure, all goals of the Ecocity Standards. Farmland preservation is key to this strategy because if helps concentrate growth while also sequestering carbon, providing local food security, and supporting the protection of water, air, habitat and outdoor recreational resources. The American Farmland Trust (AFT) has conducted studies quantifying how much greenhouse gas (GHG) emissions are mitigated when farms are preserved and development occurs within existing cities, where it belongs.
In 2013, researchers at the University of California – Davis published a study indicating that, acre for acre, developed land in Yolo County, California, emitted 70 times more GHG than irrigated cropland. AFT conducted subsequent studies in California and New York which similarly found that developed land generated 58 and 66 times more GHG than farmland in those two states (AFT 2023).
Since then, AFT has adapted a calculation methodology developed by the California Air Resources Board (CARB) in 2020 and updated in 2022 (CARB 2022). This methodology estimates GHG emissions avoided due to reduced vehicle miles traveled (VMT), changes in heating and electricity usage, and carbon loss avoidance in agricultural soil.
In partnership with The Conservation Fund, an AFT study estimated the GHG-emission difference between a low-density residential subdivision on a converted 103-acre farm versus an identical number of dwelling units built in an urban smart-growth development. The study found that this easement would avoid almost 20,000 metric tons (t) of CO2 equivalent emissions (CO2e) and 8 t of non-GHG air pollutant emissions while sequestering an additional 3,000 t of CO2e (assuming regenerative farming practices) over its first 30 years.
CARB has a calculator tool allowing its methodology to be applied to agricultural land easements in California. In its study of the easement on the 103-acre farm in Illinois, AFT modified the CARB tool to adjust for differences in data availability between the two states. In the process of calculating reductions in GHG emissions, these tools also estimate VMT reductions resulting from easements. In other words, developments in California may soon be able to use these tools to support proposals for using land conservation to achieve VMT mitigation requirements. However, this may require a new edition of California’s VMT Mitigation Playbook since the most recent edition, published in 2022, still considers land preservation for VMT mitigation as an option that is “Under Development”.
Land preservation underpins many of the Ecocity Standards from compact, energy-efficient urban form and environmentally-friendly transportation to the protection of biodiversity, water resources, soil and food. The ability to mitigate VMT and GHG through land preservation will rekindle interest in conservation and hopefully reverse or at least slow down the sprawl that been a big contributor to climate change and many other planetary threats.
References
American Farmland Trust. 2023. Protecting farmland, protecting the climate. Accessed 7-30-23 at https://farmland.org/project/avoided-conversion/.
California Air Resources Board. 2022. Quantitative Methodology: Agricultural Lands Conservation Easement. Access 7-30-23 at https://ww2.arb.ca.gov/sites/default/files/auction-proceeds/alc_qm_final_2022.pdf.
