Climate impact of cropping systems including satellite-based albedo

Background

Agricultural land use and management decisions affect global climate due to emissions and removals of greenhouse gases (GHG) and changes in land surface properties. Achieving higher reflectivity on agricultural land has the potential to mitigate local heat waves and global warming. Strategies to increase the albedo of existing croplands include choosing reflective cropsor varieties, adapting the timing of field operations, retaining residues, avoiding tillage, or growing cover crops on dark soils. Some measures have been attributed benefits in terms of both albedo and GHGbudget, such as growing cover crops, perennial energy crops, or certain reflective energy crops. However, the strengths of either effect depends on local conditions (soil type, climate), type of transformation (previous and alternative land use) and implementation (duration, timing). Further research is needed to elucidate albedo and GHGrelated effects in cropping systems in consideration of agricultural conditions.

Aims

The aim of the work in this area isto improve the understanding of how albedo change contributes to the life cycle climate impact of cropping systems, considering spatial and temporal variation. Field stations provide high-resolution measurements of albedo at selected sites with known land use and management. Yet, their coverage is insufficient to capture heterogeneity due to the combined effects of temperature, precipitation, soil type, topography, crop and management. Remote sensing offers consistent long-term estimates of surface albedo to capture spatial and temporal patterns.

Approaches

For major crops cultivatedin southern Sweden, we modelproduction of inputs, field operations, soil nitrogen and carbon balances, and albedo change compared to semi-natural grassland. Crop-specificdailyalbedo isobtainedby combiningthe MODIS BRDF/Albedo productwith geodataof agricultural land use in Sweden in 2011-2020.We analyzeseasonal patterns in albedo, and variabilityacross crops, years and sites. GHG fluxes areestimated relying on regionally-disaggregated statistical data and models.To our knowledge, this is thefirst attempt to quantify effects of crop specific albedo and GHG for a range of agricultural land uses, considering regional conditions. The results elucidate climate impacts of current cropping systems in the region, and are useful to constrain expectations on the climate change mitigation potential of existing agricultural land. The resultscan be usedin the context ofenergy or food systems.

Keywords

cropland, land use, land management, albedo, climate impact, LCA

Project leaders

Per-Anders Hansson , SLU

Other project members

Petra Sieber, SLU, Niclas Ericsson, SLU, Torun Hammar,RISE