Carbon footprint of shifting cultivation landscapes: current knowledge, assumptions and data gaps

Abstract

Shifting cultivation, a rotational land use system widely practiced in tropical regions, is often blamed for contributing to climate change due to the perceived association with deforestation and resulting greenhouse gas (GHG) emissions from slash and burn activities. This concern is often used to justify the implementation of national land use policies aiming at restricting or eradicating shifting cultivation while encouraging alternative land use systems. However, the contribution of shifting cultivation to global climate change is questionable. This study summarizes the available - and unavailable - data and knowledge required to calculate the carbon footprint (CFP) of shifting cultivation and highlights the methodological challenges and problematic assumptions that lie therein. Data on carbon stocks of fallows are found to be incomplete with large unexplained variation in the relationship between fallow age and carbon stocks of above- and belowground vegetation, and studies from Africa are under-represented. Knowledge of GHG emissions during burning is limited and associated with unsubstantiated assumptions on combustion completeness and emissions factors that represent important sources of uncertainty. Data on the global extent of shifting cultivation is coarse, and spatially explicit data on the rotation intensity of these systems is unavailable, thus hindering any upscaling of CFP calculations. Finally, it is concluded that the contribution of shifting cultivation to deforestation remains unclear, with remote sensing-based studies likely overestimating the scale of this due to methodological flaws. This review calls for caution when interpreting data on GHG emissions from shifting cultivation and suggests ways of addressing the identified data gaps.

Keywords

Land use systems / greenhouse gas emissions / carbon stocks / soil organic carbon / above- and belowground biomass / carbon sequestration / fallow regrowth / subsistence agriculture

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