Abstract
This study investigates the extent to which land use and management transitions on Vermont’s farmland could sequester atmospheric carbon in the soil. We weigh the sequestration potential of several types of regenerative agricultural practices against both business as usual and afforestation scenarios using the Rothamsted Carbon Model. We split the study area into 13 Ecoregions for a finer spatial scale of analysis, with key climate, soil, and land use data specified for each. Empirical soil laboratory data are used to initialize the model to mirror current conditions under each of three agricultural land uses (crops, hay, and pasture) in each Ecoregion. We consult experts as well as the literature to parameterize the anticipated effects of alternative agricultural management practices on soil carbon inputs. In the simulation runs, we find that all non-business-as-usual scenarios sequester carbon over time, with a higher rate of sequestration in the decades immediately after a land use or management change. Among the regenerative agriculture scenarios, conversion to rotational grazing offers the highest soil carbon sequestration potential, at 1,269 kt, or 5.3% above current stocks after ten years. Of all scenarios, afforestation of farmland to non-harvested forest stores the most soil carbon, increasing stocks by 6.5% after ten years, and continuing to sequester at a high rate many decades into the future. We discuss tradeoffs and policy implications, especially in the context of the 2020 Vermont Global Warming Solutions Act, and suggest that payments for ecosystem services for farmers sequestering carbon may have strategic value.
Generated Summary
This study investigates the potential for soil carbon sequestration through regenerative agriculture in Vermont, utilizing the Rothamsted Carbon Model (RothC). The research explores the impact of various regenerative agricultural practices on carbon sequestration, comparing them with business-as-usual scenarios and afforestation. The study area is divided into 13 Ecoregions to provide a finer spatial scale analysis, incorporating key climate, soil, and land use data. Empirical soil data are used to initialize the model, reflecting current conditions under different agricultural land uses (crops, hay, and pasture). The study consults expert opinions and existing literature to parameterize the anticipated effects of alternative agricultural management practices on soil carbon inputs. The simulation runs are conducted to assess the temporal dynamics and magnitude of carbon sequestration under different scenarios, including changes in land use and management. The study aims to provide insights into how farmland management and land use transitions can contribute to mitigating climate change and inform policy decisions related to carbon sequestration strategies. The methodology involves integrating GIS data, empirical soil measurements, and an iterative spinup procedure to estimate the potential for carbon sequestration.
Key Findings & Statistics
- The study area focuses on Vermont’s farmland, representing 12% of the state’s landbase.
- The research employs the Rothamsted Carbon Model (RothC) to assess the potential of Vermont’s farmland soils to sequester carbon through regenerative agriculture.
- The study area is divided into 13 Ecoregions for a finer spatial scale of analysis.
- Empirical soil laboratory data are used to initialize the model.
- The scenarios include business-as-usual, maintaining current agricultural uses with best management practices, converting all farmland to conventionally-managed pasture, and converting all farmland to intensive rotational grazing.
- The study includes afforestation scenarios as boundary objects for comparison.
- The study estimates that full adoption of regenerative practices, while maintaining existing land uses, could increase the state’s total SOC stocks by about 5% over current levels at the 50-year mark.
- A full transition to intensive rotational grazing could increase SOC by 11% at the 50-year mark.
- Transitioning all agricultural land to old-growth forest could increase the state’s SOC stocks by 17% over the 50-year period.
- Vermont emits approximately 5.9 megatonnes of CO2 annually.
- The study’s findings suggest that rotational grazing and afforestation could offset 4-6% of total statewide emissions in the initial years.
- The study finds that rotational grazing could offset around two to four percent of annual statewide emissions over the next century, whereas full afforestation of farmland could sequester up to seven percent over that timeframe.
- The “four per mille” initiative suggests that 20–35% of all GhG emissions may be offset by SOC sequestration (if emissions targets are met).
- Maintaining current agricultural land uses with regenerative best management practices may collectively earn Vermont farmers $9.8 million over ten years.
- Full conversion of all agricultural land to rotationally-grazed pasture could bring in $25.4 million over that period; and full afforestation as much as $31.2 million.
Other Important Findings
- All non-business-as-usual scenarios sequester carbon over time.
- Conversion to rotational grazing offers the highest soil carbon sequestration potential.
- Afforestation of farmland to non-harvested forest stores the most soil carbon.
- The rate of sequestration is higher in the decades immediately after a land use or management change.
- Humus is still increasing at the end of the 100-year model run.
- The study highlights that large-scale shifts in land use to well-managed perennial forage or afforestation could be more potent.
- The study finds that the best strategy for long-term sequestration would be old-growth afforestation, which is more effective with emissions targets.
- The research points out that, in the case of Vermont, converting land currently in corn silage to pasture-based livestock production would not necessarily deprive Vermonters of staple grains or vegetables, but simply shift the management system to a more regenerative model.
- The study supports the view that farmland SOC sequestration has significant potential as part of a wider effort to mitigate climate change in Vermont.
Limitations Noted in the Document
- The study focuses narrowly on SOC changes from land use and management transitions on Vermont farmland and does not consider other factors for the regional C balance.
- RothC only models SOC in the topsoil and does not include C in deeper soil strata or C stored as above-ground plant biomass, which, for forests, can be 21-48% of total C stocks.
- The model also does not account for differences in emissions from agricultural management; for example, higher stocking rates lead to greater methane emissions from enteric fermentation, which may offset soil C gains.
- The study does not consider C dynamics stemming from non-agricultural land uses.
- The study’s spinup procedure implicitly assumes that C stocks may fluctuate throughout each year, but will not rise or fall in the long run, which may lead to over- or under-estimations.
- The study assumes static land uses on each field year-on-year, which may lead to over- or under-estimations of SOC sequestration.
- The scenarios assessed simply assume the same type of wholesale change to all farmland simultaneously, which may not reflect real-world adoption patterns.
- The purpose of these scenarios is not to represent a realistic policy prescription or course of action per se.
Conclusion
The study underscores the potential of regenerative agriculture and land use changes in Vermont for long-term atmospheric carbon sequestration, while acknowledging the complexities and limitations of such initiatives. The results clearly indicate that changes in agricultural management, especially a shift towards pasture-based livestock production and afforestation, can play a significant role in offsetting emissions. The study highlights the importance of considering the timeframe for carbon sequestration. Although regenerative practices may yield immediate benefits, the most substantial and long-term sequestration potential appears to be associated with afforestation and conversion to well-managed perennial forages. The research emphasizes the need to consider tradeoffs between food security, land use, and greenhouse gas mitigation. The study suggests that policymakers should consider SOC sequestration alongside other strategies to decrease emissions. While the study’s projections are modest compared to broader initiatives, the findings stress that incentivizing regenerative practices and afforestation, such as through payments for ecosystem services, could be a valuable strategy. This approach offers multiple co-benefits for soil health, water quality, and rural economies. The study’s methodology is designed to be extensible to other regions. Future research should focus on more realistic scenarios, including tradeoffs between intensive agricultural production and afforestation, along with a deeper analysis of emissions intensity. In conclusion, the study highlights the promise of regenerative agriculture and land use changes in Vermont, but also emphasizes the need for a holistic approach that considers both environmental and socio-economic factors for effective and sustainable climate mitigation strategies.
IFFS Team Summary
- Article shows that long term Afforestation without tree harvest (which could include reforestation) sequesters far more carbon compared to any form of optimized / rotational grazing
- It shows effect of SOC (Soil Organic Carbon) increase from ruminant production vs afforestation
- Afforestation shows indefinite SOC increase rates, vs rotational grazing which will reduce / plateau
- But does not show effect of
- Massive carbon sequestration in trees and roots in afforestation
- Increased enteric methane emissions from grazing cattle vs feeding them crops
- Decreased stocking rates and lower meat production from most regenerative grazing studies which leads to higher emissions per unit of meat
- Increased land use / deforestation when switching from feed crops to grazing
- Cropping systems are considered here for animal feed, not human food (which is exponentially more efficient)
