How to account for Land Use Change emissions in multiple cropping systems?
Implementation of the Crop System Efficiency Index
With increasing global food demand, land use efficiency gains are part of the solution to halt deforestation and other natural land conversions for agricultural land. Multiple cropping is a practice, where a plot of land is subsequently planted with varying crops and harvested multiple times in a year. This practice is increasingly applied worldwide, contributing to increasing harvested areas without demanding additional agricultural land. However, in the Land Use Change (LUC) methodology the multiple cropping scenarios have not been considered yet, leading to inaccurate LUC emission calculations, especially for areas in the world where multiple cropping practices are often applied. Therefore, we’ve investigated the opportunities to include multiple cropping and make more fair calculations, by applying the ‘Crop System Efficiency Index’ (CSEI).
In this article we’d like to take a moment to explain the proposed methodology and the implementation for the latest LUC Impact Dataset.
Multiple cropping and LUC emissions
Currently there is no uniform guideline on how to account for multiple cropping in LUC methodologies. Within Life Cycle Assessment (LCA) studies it is often required to report the emissions emerging from LUC, such as the clearance of forests to cultivate crops, separately. Blonk’s LUC Impact tool is a web-based solution, supporting the calculation of direct and statistical LUC emissions. It also provides the LUC emission inputs for Lifecycle Inventory databases, such Agri-footprint and GFLI. However, multiple cropping activities have previously not been considered in the implemented methodology. The assumption that the occupation duration for a harvest of temporary crops is always 1 year, led to an overestimation of both the LUC emissions and the land occupation impact, especially in countries where multiple cropping practices are ubiquitous. Multiple cropping primarily occurs in tropical and subtropical regions where there is a sufficient long rainy season or suitable irrigation to cultivate two or three crops sequentially within a single agricultural year. An example is a crop rotation system of planting soybeans during the summer months, harvesting the crops in late summer or early fall, and planting maize in the same field after and harvesting this in early spring.
Implementation of Crop System Efficiency Index
To represent multiple cropping practices more accurately in LUC and land occupation calculations, we propose the use of the ‘Crop System Efficiency Index’ (CSEI). What we are calculating with the CSEI, is the (average) length of the harvest cycle of temporary crops (in yr/harvest). The index considers both land efficiency gains from multiple cropping, and efficiency losses due to temporary fallow land. A possible solution for the calculation of land occupation and transformation related to crop production in countries with more precision will be proposed next, using a consistent and already-used data set (FAOSTAT).
As only temporary (and no permanent) crops are associated with multiple cropping (and fallow land), we need to use information of the hectares of crops harvested in a country, and determine which crops belong to a productive period < 5 years: these are considered “Temporary Crops”. In this category we can find annual and perennial crops (according to the FAO definition).
The other components required are the Temporary Crops and Temporary fallow areas from FAOSTAT. With this information we can start to calculate the CSEI.
Calculating the Crop System Efficiency Index
1. Multiple Crop Index
The calculation starts with the Harvested area of temporary crops and Temporary Cropland to decide if multiple cropping is the case.
In case the result is smaller than 1, this is related to multiple cropping: the sum of harvested area for temporary crops is larger than the total temporary cropland.
The reason for an MCI of greater than 1, is not always clear or straightforward. Comparing national statistics with FAO data for the Netherlands showed that the harvested area of some fodder crops was not included in the harvested cropland in FAO data but was included in the total temporary cropland area. This example shows that a MCI > 1 can be associated with incomplete FAO data and does not always point to land use inefficiencies. Therefore, the following rule is implemented:
If MCI > 1, the value should be adjusted to 1, leading to a MCI corrected value (MCIc).
2. Follow Land Index
As fallow land is associated with crop rotation and multiple cropping,
it is allocated to all temporary cropland. This is expressed in the Fallow Land Index (FI).
3. Crop System Efficiency Index
In the last step the adjusted Crop System Efficiency Index can be obtained:
Possible results:
- CSEI < 1: Multiple cropping is the case, more than one crop is produced and harvested per year, per hectare. The land occupation value calculated is multiplied by this value.
- CSEI = 1: There is no multiple cropping, or the efficiency gains from multiple cropping are counteracted by efficiency losses from fallow land. The land occupation value should not be modified.
- CSEI > 1: Per hectare harvested, more than 1 hectare should be destinated to this process. The land occupation value should be multiplied by this value.
Definitions & Concepts
- Temporary Cropland: Land used for crops with a less-than-one-year growing cycle, which must be newly sown or planted for further production after the harvest. Some crops that remain in the field for more than one year may also be considered as temporary crops e.g., asparagus, strawberries, pineapples, bananas, and sugar cane. Multiple-cropped areas are counted only once.
- Temporary Fallow Land: Land that is not seeded for one or more growing seasons. The maximum idle period is usually less than 5 years. Land is also considered as ‘temporary fallow’ if it is sown for the exclusive production of green manure. Land remaining fallow for too long may acquire characteristics requiring it to be reclassified, as for instance “Permanent meadows and pastures” if used for grazing or haying.
- Harvested area of temporary crops: Surface of crops harvested with a productive period < 5 years between seedling and the final harvesting of the crop. This category includes both annual and perennial crops, like Maize and Banana.
Application of the Crop System Efficiency Index
One key step is to determine in which cases the Crop System Efficiency Index improves the results, and in which cases the use of the index is unsuitable. The CSEI should affect only the environmental impact linked to a proportion of time that the land is occupied by a harvested crop. An example is emissions linked to Land Use Change: if there are 2 crops produced in a year per hectare, the amount of LUC emissions will be split by 2 (50 % for each crop). Within Blonk we apply the CSEI in various models, such as Land Use Change, Peat, Land Occupation, Carbon Sequestration and Land Transformation.
Updated LUC Impact Dataset
Currently, we are updating the LUC Impact Dataset and implementing the Crop System Efficiency Index. The LUC Impact Dataset provides LUC greenhouse gas emissions for 9,000+ crop-country combinations, including emission results calculated using both linear and equal amortization in compliance with footprinting standards such as PAS2050-1 and SBTi FLAG.
We expect to release an updated version (version 2024) by the end of February 2024.
More information
Get in touch
Iana Salim
Do you have any questions on the Crop System Efficiency Index and the implementation into Blonk’s LUC Impact products? Get in touch with Iana.