Global crop yield response to extreme heat stress under multiple climate change futures

TLDR

Extreme heat stress during crop reproductive periods threatens productivity, and the increasing frequency and severity of such events are projected to harm global crop yields and food security. The study uses the PEGASUS global crop model to quantify the impacts of extreme heat stress on maize, spring wheat, and soybean yields across 72 climate change scenarios for the 21st century. Using PEGASUS, the authors simulate 72 climate scenarios to assess how extreme heat stress affects maize, spring wheat, and soybean yields worldwide. Results indicate maize yields will worsen under all RCPs, while spring wheat and soybean yields improve globally through the 2080s due to CO₂ fertilization, yet tropical and subtropical regions may still decline; extreme heat stress at anthesis could double maize losses, halve wheat gains, and quarter soybean gains, with CO₂ mitigation policies potentially averting most losses and regional disparities highlighting greater impacts on major producing regions and low‑income countries.

Abstract

Extreme heat stress during the crop reproductive period can be critical for crop productivity. Projected changes in the frequency and severity of extreme climatic events are expected to negatively impact crop yields and global food production. This study applies the global crop model PEGASUS to quantify, for the first time at the global scale, impacts of extreme heat stress on maize, spring wheat and soybean yields resulting from 72 climate change scenarios for the 21st century. Our results project maize to face progressively worse impacts under a range of RCPs but spring wheat and soybean to improve globally through to the 2080s due to CO2 fertilization effects, even though parts of the tropic and sub-tropic regions could face substantial yield declines. We find extreme heat stress at anthesis (HSA) by the 2080s (relative to the 1980s) under RCP 8.5, taking into account CO2 fertilization effects, could double global losses of maize yield (ΔY = −12.8 ± 6.7% versus − 7.0 ± 5.3% without HSA), reduce projected gains in spring wheat yield by half (ΔY = 34.3 ± 13.5% versus 72.0 ± 10.9% without HSA) and in soybean yield by a quarter (ΔY = 15.3 ± 26.5% versus 20.4 ± 22.1% without HSA). The range reflects uncertainty due to differences between climate model scenarios; soybean exhibits both positive and negative impacts, maize is generally negative and spring wheat generally positive. Furthermore, when assuming CO2 fertilization effects to be negligible, we observe drastic climate mitigation policy as in RCP 2.6 could avoid more than 80% of the global average yield losses otherwise expected by the 2080s under RCP 8.5. We show large disparities in climate impacts across regions and find extreme heat stress adversely affects major producing regions and lower income countries.