Complementarity in mid-point impacts for water use in life cycle assessment applied to cropland and cattle production in Southern Amazonia

Southern Amazonia has been the centre of a large expansion of cropland and cattle production into newly deforested areas in both the Amazon and Cerrado biomes. While this expansion has had noted impacts on the regional water cycle, little information is currently apparent in lifecycle impact assessments of both cropland and cattle products.

This study applies existing models to quantify the mid-point impacts of water consumption and land occupation of cropland and cattle following distinct production systems that rely on agricultural extensification and intensification (cropland irrigation, and increased pasture productivity). It focuses on both terrestrial and aquatic flows, in order to highlight complementarity in current impact assessment models, expressed through the several impact categories that are introduced here: Water Scarcity Footprint, Terrestrial Green Water Flows, Precipitation Reduction Potential, River Blue Water Production, Groundwater Recharge Potential, and Runoff Reduction Potential.

The results show conditional changes in the magnitude and sign of potential impacts when comparing rain-fed to irrigated cropland, particularly in the Cerrado biome. Cropland irrigation can increase atmospheric and terrestrial water flows as expressed through Precipitation Reduction Potential (−95 m³ ha⁻¹), River Blue Water Production (299 m³ ha⁻¹), or Groundwater Recharge Potential (215 m³ ha⁻¹). Moreover, increased pasture productivity led to an overall decrease in mid-point impacts of cattle production on the water cycle.

While this study provides additional insight into the effects of cropland and cattle production systems in Southern Amazonia, our results also highlight the complementarity of existing mid-point impacts towards a better representation of freshwater use in life cycle assessment.

The article is open access until 10 May 2019.