Uncovering the moisture and heat sources to croplands during agricultural failure events

Dry and hot climate anomalies threaten rainfed agricultural productivity worldwide. Land–atmosphere feedbacks play a critical role during these abnormal weather events; for example, dry soils reduce evaporation and enhance sensible heating over the land surface, thereby amplifying air temperatures and water deficits for crops, consequently leading to agriculture failure. Moreover, these anomalies of moisture and heat upwind can be translated into downwind regions, thus leading to the spatial propagation of crop-adverse climate conditions. 

In this presentation, we analyse precipitation and temperature anomalies associated with crop failure events over the world’s largest 75 rainfed breadbaskets. Then the spatio-temporal origins of moisture and heat over these breadbaskets are determined using a novel atmospheric Lagrangian modelling framework along with satellite observations. Results indicate that upwind and local land–atmosphere feedbacks together cause lower moisture and higher heat transport into these breadbaskets, leading to decreases in yield of up to 40%. By zooming into the Southeastern Australia wheat belt as an example, known for experiencing recurrent droughts and heatwaves, we provide a detailed analysis of the anomalies of water and energy fluxes and atmospheric circulation and their impacts on moisture and heat sources. We find a substantial impact of advection of dry and hot air from upwind terrestrial regions, particularly during crop failure events, i.e., 1994, 2002, and 2006. Persistent high-pressure systems significantly alter moisture and heat imports into the wheat belt during these events, with upwind drought conditions intensifying rainfall deficits and heat stress in the agricultural region.

Our study suggests the potential for upwind land management to mitigate agricultural losses in rainfed, water-limited regions. Further understanding the intricate relationships between upwind and local influences on global breadbaskets, and specific regions like Southeastern Australia, may provide crucial insights for developing adaptive measures to avert food shortages in the face of a changing climate.