Whole farm planning raises profit despite burgeoning climate crisis.

The climate crisis challenges farmer livelihoods as increasingly frequent extreme weather events impact the quantum and consistency of crop production. Here, we develop a novel paradigm to raise whole farm profit by optimising manifold variables that drive the profitability of irrigated grain farms. We build then invoke a new decision support tool-WaterCan Profit-to optimise crop type and areas that collectively maximise farm profit. We showcase four regions across a climate gradient in the Australian cropping zone. The principles developed can be applied to cropping regions or production systems anywhere in the world. We show that the number of profitable crop types fell from 35 to 10 under future climates, reflecting the interplay between commodity price, yield, crop water requirements and variable costs. Effects of climate change on profit were not related to long-term rainfall, with future climates depressing profit by 11-23% relative to historical climates. Impacts of future climates were closely related to crop type and maturity duration; indeed, many crop types that were traditionally profitable under historical climates were no longer profitable in future. We demonstrate that strategic whole farm planning of crop types and areas can yield significant economic benefits. We suggest that future work on drought adaptation consider genetic selection criteria more diverse than phenology and yield alone. Crop types with (1) higher value per unit grain weight, (2) lower water requirements and (3) higher water-use efficiency are more likely to ensure the sustainability and prosperity of irrigated grain production systems under future climates.