Global Flux-Based Assessment Reveals Declining Ozone Risk for Wheat in Future Climate Change Scenarios

Area of Science:

• Environmental Science
• Agricultural Science
• Climate Science

Background:

• Tropospheric ozone (O3) is a significant air pollutant impacting crop yields and global food security.
• Current assessments often use exposure-based metrics, neglecting crucial plant-environment interactions that regulate O3 uptake by plants.

Purpose of the Study:

• To conduct a global, flux-based assessment of future O3 risk for wheat (Triticum aestivum) from 2000 to 2100.
• To quantify phytotoxic O3 dose (POD6) and production losses under various climate scenarios (SSPs) and explore influencing factors.
• To analyze regional trends and the impact of soil water, CO2, radiative forcing, and emission policies on O3 risk.

Main Methods:

• Utilized a dual-sink dry deposition model driven by Earth System Models from CMIP6.
• Simulated O3 risk for wheat under three Shared Socioeconomic Pathways (SSPs): SSP1-2.6, SSP3-7.0, and SSP5-8.5.
• Incorporated factors like soil water availability, atmospheric CO2, radiative forcing, and emission policies into the risk assessment.

Main Results:

• A general decline in O3 risk is projected globally, but with significant regional variations.
• Under SSP1-2.6 (strong emission policies, low radiative forcing), global mean wheat production losses decrease significantly by the end of the century.
• SSP3-7.0 (weak emission policies, high radiative forcing) may increase O3 risks in South and East Asia, South America, and Sub-Saharan Africa.
• Increasing CO2 concentrations are likely to mitigate O3 risk by reducing stomatal conductance, though hotspots may persist near the Tibetan Plateau.

Conclusions:

• Future O3 risk to wheat varies considerably depending on socioeconomic pathways, particularly emission policies and radiative forcing.
• Region-specific mitigation strategies are essential to reduce O3 damage to wheat, considering the localized impacts of climate change and air pollution.
• The study highlights the importance of flux-based metrics over exposure-based metrics for accurate O3 risk assessment in agriculture.