Abstract

Keywords:Atmospheric; Environment; Subtropical cereal systems; Climate; Cereal crops; Agro-ecologies

Introduction

Global atmospheric CO₂ has risen from ~280 ppm pre-industrial to >420ppm today; levels projected for mid-century (≈550-650 pm under many scenarios) will continue to change crop environments through both direct CO₂ effects and through the broader climate shifts that CO₂ drives. Cereal crops (wheat, rice, maize, barley, sorghum) supply the bulk of calories for billions; thus, small changes in yield or nutrient content cascade into major food-security and public-health outcomes. Understanding the net effect of eCO₂ plus climate change requires synthesizing controlled-environment, FACE (Free-Air CO₂ Enrichment) and field studies, and considering interactions with nitrogen availability, warming, drought, pests and management [1,2].

Direct Physiological Effects of Elevated CO₂ on Cereals

In C₃ cereals eCO₂ typically increases net photosynthesis, improves water-use efficiency via reduced stomatal conductance, and when other resources are not limiting can increase biomass and grain yield [1,3]. FACE syntheses show mean yield increases for C₃ species, but responses vary widely (often ~10-25% for wheat/rice under favourable N and water) and are frequently smaller under high soil N limitation or low light. C₄ cereals (e.g., maize, sorghum) show much smaller direct gains because their photosynthetic pathway already concentrates CO₂, though indirect benefits via improved water relations can occur under drought. Importantly, pot/enclosure experiments sometimes overestimate field responses; multi-site FACE trials provide the most realistic field evidence and indicate more modest, site-specific gains [1,3].

Grain Quality: Protein and Micronutrients

A consistent finding across FACE and field studies is that eCO₂ reduces grain protein concentration and decreases concentrations of key micronutrients particularly iron and zinc in many staple cereals and legumes [4,5]. Proposed mechanisms include carbohydrate “dilution” (increased carbohydrate lowers relative N and mineral concentration), altered root uptake and translocation (reduced transpiration and mass flow), and shifts in tissue allocation. For wheat, meta-analyses report yield increases (~10-16%) accompanied by protein declines (≈5-10% or more depending on cultivar and N supply), with consequences for processing and baking quality. Nutritional modelling indicates these declines could push millions closer to deficiency thresholds for Fe and Zn in vulnerable populations, aggravating “hidden hunger” even where caloric production rises.

Interactions with Warming, Drought and Pests

CO₂ effects do not act in isolation. Warming shortens crop phenology (reducing grain fill), raises heat-sterility risk (especially around anthesis), and can reduce yields even when CO₂ would otherwise stimulate growth [2]. In some cases, eCO₂ partially ameliorates heat stress on photosynthesis and improves plant water status offering a buffer against moderate warming but this buffer is limited and cannot fully offset heat-related yield losses or quality declines at higher temperatures [6]. Drought interactions are complex: under moderate drought, eCO2 induced water savings may protect yields, but severe drought, nutrient limitation, or increased pest/disease pressure (which can change under climate) can negate CO₂ benefits. Accordingly, IPCC assessments emphasise that climate change will increasingly reduce yields in many tropical/subtropical cereal systems without adaptation [2].

Management and Breeding Responses

Mitigating nutrition losses and stabilizing yields under eCO₂ + climate change requires multi-pronged action:
a) Breeding for nutrient resilience: select cultivars that maintain grain N, Fe and Zn under eCO₂ while retaining yield and heat/drought tolerance (biofortification, marker-assisted breeding).
b) Optimized nutrient management: adequate and timely N (and micronutrient) supply can reduce protein dilution; targeted Zn/Fe fertilization and soil health measures improve uptake.
c) Agronomic adjustments: altered sowing dates, cultivar choice, irrigation scheduling and integrated pest management reduce exposure to heat/drought peaks.
d) Post-harvest and dietary policies: fortification, diversification and social programs buffer nutritional shortfalls. Field and FACE evidence indicates management often modulates the magnitude of eCO₂ effects, so locally tailored interventions are essential [1,4].

Policy Implications and Research Priorities

Policy should recognise that CO₂-driven yield gains are not a substitute for emission reductions and can produce perverse nutritional outcomes. Priorities include expanding FACE and multifactor field trials across agro-ecologies (to capture interactions), investing in breeding for combined yield-nutrient-heat/drought resilience, strengthening soil and nutrient management extension, and integrating nutrition outcomes into crop-climate models and food-security planning. Surveillance of crop nutrient trends and population micronutrient status must be scaled up to detect and address emerging deficiencies. Finally, strong greenhouse-gas mitigation remains essential to limit the magnitude of climate impacts on cereals and global food systems [2,4].

Conclusion

Elevated CO₂ will continue to reshape cereal systems in complex and sometimes counter-intuitive ways: while modest, context-dependent yield gains are likely for many C₃ cereals, these are frequently accompanied by declines in grain protein and essential micronutrients, worsening hidden hunger even where calories increase. Climate warming and more frequent extremes (heat, drought, pests) often negate or overwhelm CO₂-driven benefits, so any yield gains are fragile and regionally variable. Tackling these dual challenges requires coordinated action across breeding (prioritizing combined yield, heat/drought tolerance and nutrient resilience), agronomy (optimized nutrition, water and pest management), surveillance (routine monitoring of crop nutrient trends and population micronutrient status) and policy (food-system diversification, fortification and social safety nets). Research must expand multi-factor, multi-site experiments and integrate nutrition into crop–climate models to guide targeted interventions. Above all, emissions mitigation remains indispensable: limiting the magnitude of climate change is the most effective way to safeguard long-term cereal security and nutrition.

Recommendation

To enhance the effectiveness of AI integration in assessing the effects of rice production on Nyando Wetland, Kisumu County, several key strategies should be adopted.
i. Investment in AI-driven remote sensing and Geographic Information Systems (GIS) should be prioritized to enable continuous monitoring of wetland changes and water quality.
ii. Collaboration between government agencies, research institutions, and farmers is essential for data sharing and capacity building to ensure proper AI application in sustainable agriculture.
iii. Policymakers should establish regulatory frameworks to guide ethical AI deployment, ensuring that technological advancements align with environmental conservation goals.
iv. Financial and technical support should be extended to local farmers to facilitate the adoption of AI tools, particularly in predictive modeling for sustainable land and water resource management.
v. Incorporating AI in decision-making processes through real-time data analytics can enhance policy formulation, balancing rice production with wetland conservation efforts. By implementing these strategies, AI can serve as a powerful tool for mitigating the environmental impact of agriculture while promoting sustainable development in Nyando Wetland.

References

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2. Intergovernmental Panel on Climate Change (2022) Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. In: HO Pörtner et al. (Eds.). Cambridge University Press.
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