Quantification of Soil Carbon Sequestration Potential in Dryland Micro-Rainwater Harvesting Structures

Abstract

Arid regions cover around one third of the Earth’s land surface, including 80% of Jordan. These regions may be suitable for the storage of carbon in their soils, providing environmental and economic benefits. This study was conducted to quantify the potential for soil carbon sequestration in dryland micro-rainwater harvesting (Vallerani) structures. The effect of changing climatic and land management conditions was investigated at the International Centre for Agricultural Research (ICARDA) field site in Al Majidiyya, Jordan. Field data was combined with modelling of carbon stocks using RothC-26.3 to meet this aim. Upscaling of the results and consideration of resultant ecosystem services was completed using the inVEST modelling tools. Results suggest that implementing Vallerani structures can lead to an increase in carbon stocks of 1.75 t/ha at the structure ridge and 4.26 t/ha in the structure furrow over a ten-year period. Upscaling these results shows a sequestration potential of 7.9 ± 0.76 t C at the study site, and almost 3 million tons across the Badia as a whole. Ecosystem service modelling demonstrates a potential economic cost of this sequestration to Jordan of as little as $17/ha, covering a large proportion of the implementation costs, even before benefits from increased food production, habitat improvement and other ecosystem services are considered. These results demonstrate that dryland water harvesting offers the potential for significant carbon sequestration compared to natural conditions. Further work should focus on constraining the economic costs and benefits to further expanding the water harvesting structures, as well as the impact of climate change on these predictions.