Current and future ozone risks to global terrestrial biodiversity and ecosystem processes.

Area of Science:

• Environmental Science
• Ecology
• Atmospheric Chemistry

Background:

• Ozone (O3) exposure risks to individual plant species are known, but impacts on terrestrial biodiversity and ecosystem processes remain understudied.
• Future atmospheric O3 levels are projected to change due to air quality and climate policies, potentially altering ecosystem feedbacks.
• Understanding O3 impacts is crucial for predicting future terrestrial ecosystem health and atmospheric interactions.

Approach:

• Utilized the Community Earth System Model (CESM) for global O3 simulations under different emission scenarios (RCP8.5 and RCP4.5).
• Analyzed O3 exposure levels in terrestrial ecoregions (ERs) for the years 2000 and 2050.
• Synthesized findings from experimental studies on O3 effects on plant growth, reproduction, species composition, and belowground processes.

Key Points:

• In 2000, 40% of Global 200 terrestrial ecoregions exceeded O3 thresholds for ecological risk, with high exposures in North America, Southern Europe, and Central Asia.
• O3 adversely affects plant growth, flowering, species richness, and alters water regulation, pollination, and pathogen development.
• Belowground impacts include changes in soil invertebrates, litter quality, decomposition, nutrient cycling, and carbon pools, with effects potentially taking decades to manifest.

Conclusions:

• CESM simulations for 2050 predict increased O3 exposure in most biomes under RCP8.5.
• Even with RCP4.5 policies, 50% of ecoregions may experience increased O3 exposure, indicating persistent risks.
• O3 risks to biodiversity and ecosystem processes are likely to persist across trophic levels and require greater attention in future assessments.