Future soil erosion of shifting cultivation on hillslopes – modeling interactions between slope steepness, fallow periods, and climate change

Abstract

Shifting cultivation, also known as slash-and-burn agriculture, on steep terrain has been criticized for causing high rates of soil erosion thus promoting land degradation in South and Southeast Asia. Particularly, short fallow periods resulting from increasing land pressure are suspected of accelerating degradation processes. In addition, the rising frequency of high-intensity precipitation events associated with climate change can be expected to further increase the pressure on shifting cultivation. However, abandonment of shifting cultivation has turned out to be hardly feasible or desirable, particularly, where it provides food security and cultural identity to the tribal population, as is the case in Northeast India. This raises the question how increasing pressure from reduced fallow periods and climate change will affect future soil erosion of uphill shifting cultivation systems. As measured data on these interactions are not available, we applied a modeling approach to identify trends in soil erosion for different slope inclinations, fallow periods, and climate change scenarios. We used the Environmental Policy Integrated Climate (EPIC) Model to simulate daily soil loss for three different climate scenarios (SSP126, SSP370, SSP585) derived from five climate models for the near (2021-2050) and far (2071-2100) future. Simulations were carried out for six collected soil profiles, short, medium, and long fallow periods, and slope inclinations up to 70 %. Our results indicate a negative, non-linear relationship between the length of the fallow period and erosion, with soil loss being more than twice as high for systems with a 10-year compared to a one-year fallow regime. Further, our research demonstrates that long fallow periods can compensate, to a limited extent, for steep slopes. However, climate change, particularly under the medium-high (SSP370) and high-end (SSP585) emission scenarios, will lead to substantial increases in erosion by a factor of 2.2 and 3.1, respectively, towards the end of the century, thus reducing the possibility space for sustainable shifting cultivation.