| Symbol | Name | Value | Units |
|---|---|---|---|
| CO2_MW | ratio of molecular weight of CO2 to carbon | 44/12 | kg CO2 [kg C]-1 |
Direct Land Use Change
Methods 5.0
on-farm
non-mechanical
Emissions associated with the change from an IPCC land cover category to annual or perennial (alfalfa) cropland for a given field boundary.
Introduction
Emissions associated with Direct Land Use Change is an addition to FP v5, using a method based on IPCC (2019) and ECEuropean Commission (2010). This method is a tailored implementation to represent Field to Market crops and feedback from stakeholders.
Land use change will be estimated when the Cropland Data Layer (Boryan et al. 2011) detects one of the following categories for a given field boundary, starting in the year 2008:
- Forest
- Deciduous Forest
- Evergreen Forest
- Mixed Forest
- Shrubland
- Grassland
Land use change emissions are the emissions associated with the change from one of the IPCC land cover categories shown above to annual or perennial (alfalfa) cropland for a given field boundary. The emissions account for the carbon lost from the biomass and the soil.
Methods
To develop this methodology, we used the IPCC Generic Methodologies Applicable to Multiple Land Use Categories (IPCC 2019) and the Guidelines for the Calculation of Land Carbon Stocks for the Purpose of Annex V to Directive 2009/28/EC (ECEuropean Commission 2010).
To calculate the emissions, we establish a reference land use value and the current land use value. The reference land use must have happened in the past 20 years. To calculate the amount of C stored, we use standard values that can be found in the guidelines mentioned above. A limitation is that the Cropland Data Layer can detect land use for the contiguous United States starting in 2008, representing a coverage of 16 years. At the US national level, approximately 40% of cropland is rented or leased (Bigelow 2014). It is unlikely that a grower farming a rented or leased field in 2024 would know the history of the same field starting in 2004. As a consequence, until 2028, the Cropland Data Layer will have a 1-4-year gap to meet the 20-year look-back period requirement.
Users of the FP sometimes draw field boundaries by hand rather than importing a shapefile field boundary from a farm management system. A boundary might erroneously intersect areas outside the cropland. For this reason, we propose implementing a threshold of detecting at least 10% of the area within the field boundary to be one of the categories above (forest, shrubland, etc.) before informing the user that the land use change method will be part of the field’s footprint and to review the field boundary to fix any errors. There will be a period of iteration and adjustments in the FP v5 to reach a robust methodology to implement this method.
The following equations is used to estimate the soil C stock \(CS^{soil}\) for the ith situation, i.e. reference and current land use:
\[ CS^{soil}_i = \sum_{c,s} (SOC^{ref}_{c,s} \times F^{LU}_{c,s} \times F^{MG}_{c,s} \times F^{I}_{c,s}) \]
- \(CS^{soil}_i\) = total mineral soil organic C stock at a defined time for the ith situation (tonne C ha-1)
- \(SOC_{ref}\) = the soil organic C stock for mineral soils in the reference condition (tonne C ha-1)
- \(F^{LU}\) = stock change factor for mineral soil organic C land-use systems or sub-systems for a particular land-use (dimensionless)
- \(F^{MG}\) = stock change factor for mineral soil organic C for management regime (dimensionless)
- \(F^{I}\) = stock change factor for mineral soil organic C for the input of organic amendments (dimensionless)
- \(c,s\) denotes climate regions and soil types
The biomass C stock \(CS^{veg}_i\) (tonne C ha-1) for the ith situation (reference and current land use) is taken from standard values which consider all the necessary C pools, including above and below-ground biomass, as well as living and dead organic matter. These values are selected using the information from: type of vegetation, ecological or Climate zone, and the species or the age of the plants.
Factors for both soil and biomass C stock can be found in the Guidelines for the calculation of land carbon stocks for the purpose of Annex V to Directive 2009/28/EC (ECEuropean Commission 2010).
Then, the C stock \(CS\) for the ith situation (reference and current state) is the sum of both above mentioned stock:
\[ CS_i = (CS^{soil}_i + CS^{veg}_i) \times A \times 10^{3} \]
- \(CS_i\) = C stock for the ith situation (reference and reference state) (kg C)
- \(A\) = land area of the stratum being estimated (ha)
Once soil and vegetation carbon stocks are estimated, the total emissions are computed as follows:
\[ [CO_2]^{total} = (CS_R - CS_A) \times [CO_2]^{mw} \times AEF(t) \times A \]
- \([CO_2]^{total}\) = the emissions from land use change (kg CO2 ha-1)
- \(CS_R\) and \(CS_C\) = carbon stock at reference and current situation (kg C ha-1)
- \(AEF(t)\) = allocated emission fraction for year \(t\) (dimensionless)
- \([CO_2]^{mw}\) = ratio of molecular weight of CO2 to carbon, 44/12 (kg CO2 [kg C]-1)
- \(A\) = area of the land parcel (ha)
We propose that the calculated emissions from LUC are allocated differently across the 20 years, with the impacts decreasing gradually across the period described by the following equation:
\[ AEF(t) = 0.1025 - (0.005 *t) \]
Thus, the first year after the LUC accounts for 9.75% of the total emissions, while the 20th year accounts for 0.25%. Each year represents 0.5% less emissions than the previous year. This allocation method attributes more importance to years closer to the LUC event, which follows what really happens in the natural systems.
Emissions per area and per crop production unit
Provided the area and crop yield, the annual total CO2 emissions can be computed per area and per crop production unit as follows:
\[ \begin{align} [CO_2]^{area} &= [CO_2]^{total} \times A^{-1} \\ [CO_2]^{prod} &= [CO_2]^{total} \times (Y \times A)^{-1} \end{align} \]
- \([CO_2]^{area}\) = the emissions from land use change per area (kg CO2 ha-1)
- \([CO_2]^{prod}\) = the annual total CO2 emissions per crop production unit (kg CO2 [kg crop production]-1)
- \(A\) = the area of the land parcel (ha)
- \(Y\) = crop yield (kg ha-1)
NoteExample
An land use change calculation for illustrative purposes can be found here: Supplementary Material
Constants and factors required for calculation
Vegetation carbon stock
| Type of vegetation | Ecological/Climate Zone | Species or Age | CS_veg |
|---|---|---|---|
| Cropland | Not applicable | Not applicable | 0.0 |
| Cropland (sugar cane) | Subtropical Steppe | Not applicable | 4.8 |
| Cropland (sugar cane) | Subtropical Humid Forest | Not applicable | 4.8 |
| Perennial crop | Temperate (all moisture regimes) | Not applicable | 43.2 |
| Perennial crop | Tropical (dry) | Not applicable | 6.2 |
| Perennial crop | Tropical (moist) | Not applicable | 14.4 |
| Perennial crop | Tropical (wet) | Not applicable | 34.3 |
| Perennial (coconuts) | Not applicable | Not applicable | 75.0 |
| Perennial (Jatropha) | Not applicable | Not applicable | 17.5 |
| Perennial (Jojoba) | Not applicable | Not applicable | 2.4 |
Soil SOC by climate regions and soil type
| Climate region | Soil type | SOC |
|---|---|---|
| Boreal, moist | High activity clay soils | 68 |
| Cool temperate, dry | High activity clay soils | 50 |
| Cool temperate, moist | High activity clay soils | 95 |
| Warm temperate, dry | High activity clay soils | 38 |
| Warm temperate, moist | High activity clay soils | 88 |
| Tropical, dry | High activity clay soils | 38 |
| Tropical, moist | High activity clay soils | 65 |
| Cool temperate, dry | Low activity clay soils | 33 |
| Cool temperate, moist | Low activity clay soils | 85 |
| Warm temperate, dry | Low activity clay soils | 24 |
Soil classes and soil types
| Soil_subunit | Soil_unit | Soil type |
|---|---|---|
| Af | Acrisol | Low activity clay soils |
| Ag | Acrisol | Low activity clay soils |
| Ah | Acrisol | Low activity clay soils |
| Ao | Acrisol | Low activity clay soils |
| Ap | Acrisol | Low activity clay soils |
| NA | Albeluvisol | High activity clay soils |
| NA | Alisol | High activity clay soils |
| Th | Andosol | Volcanic soils |
| Tm | Andosol | Volcanic soils |
| To | Andosol | Volcanic soils |
US Soil Map
Koppen-Geiger climate classification by county
| State | County | Code |
|---|---|---|
| Alabama | Monroe | Cfa |
| Arizona | Greenlee | Csb |
| Arkansas | Bradley | Cfa |
| California | Napa | Csb |
| Colorado | Ouray | Dfb |
| Connecticut | Middlesex | Cfb |
| Delaware | Sussex | Cfa |
| Florida | Jefferson | Cfa |
| Georgia | Gwinnett | Cfa |
| Idaho | Madison | Dfb |
Dictionary for matching Koppen-Geiger classification to climate regions
| Code | Climate Description | Climate region |
|---|---|---|
| Af | Tropical Rainforest | Tropical, moist |
| Am | Tropical Monsoon | Tropical, moist |
| Aw | Tropical Savanna (Wet and Dry Climate) | Tropical, dry |
| BWk | Cold Desert Climate | Cool temperate, dry |
| BWh | Hot Desert Climate | Tropical, dry |
| BSk | Cold Semi-Arid Climate | Cool temperate, dry |
| BSh | Hot Semi-Arid Climate | Tropical, dry |
| Csa | Hot-Summer Mediterranean Climate | Warm temperate, dry |
| Csb | Warm-Summer Mediterranean Climate | Warm temperate, dry |
| Csc | Temperate, Dry Summer, Cold Summer | Warm temperate, dry |
Factors for computing soil carbon stock
| Climate region | Land use | Management | Input | FLU | FMG | FI |
|---|---|---|---|---|---|---|
| Boreal, moist | Cultivated | Full-tillage | Low | 0.69 | 1.00 | 0.92 |
| Boreal, moist | Cultivated | Full-tillage | Medium | 0.69 | 1.00 | 1.00 |
| Boreal, moist | Cultivated | Full-tillage | High with manure | 0.69 | 1.00 | 1.44 |
| Boreal, moist | Cultivated | Full-tillage | High without manure | 0.69 | 1.00 | 1.11 |
| Boreal, moist | Cultivated | Reduced tillage | Low | 0.69 | 1.08 | 0.92 |
| Boreal, moist | Cultivated | Reduced tillage | Medium | 0.69 | 1.08 | 1.00 |
| Boreal, moist | Cultivated | Reduced tillage | High with manure | 0.69 | 1.08 | 1.44 |
| Boreal, moist | Cultivated | Reduced tillage | High without manure | 0.69 | 1.08 | 1.11 |
| Boreal, moist | Cultivated | No till | Low | 0.69 | 1.15 | 0.92 |
| Boreal, moist | Cultivated | No till | Medium | 0.69 | 1.15 | 1.00 |
References
Bigelow, Daniel. 2014. “USDA Economic Research Service-Farmland Ownership and Tenure.” https://www.ers.usda.gov/topics/farm-economy/land-use-land-value-tenure/farmland-ownership-and-tenure.
Boryan, Claire, Zhengwei Yang, Rick Mueller, and Mike Craig. 2011. “Monitoring US Agriculture: The US Department of Agriculture, National Agricultural Statistics Service, Cropland Data Layer Program.” Geocarto International 26 (5): 341358.
ECEuropean Commission. 2010. “2010/335/: Commission Decision of 10 June 2010 on Guidelines for the Calculation of Land Carbon Stocks for the Purpose of Annex v to Directive 2009/28/EC (Notified Under Document c(2010) 3751).” https://eur-lex.europa.eu/eli/dec/2010/335/oj.
IPCC. 2019. “2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories.”