Rice cultivation has emerged as the single largest source of greenhouse gas emissions from global agriculture, accounting for 43% of cropland emissions in 2020—surpassing synthetic fertilizers and drained peatlands—according to new research that fundamentally revises methane accounting from flooded rice paddies.
The finding, published in Earth.com, does not suggest that billions of people should stop eating rice. It highlights a measurement problem that has obscured rice's climate footprint and an opportunity: proven agronomic solutions exist that could dramatically cut emissions without reducing yields.
Flooded rice fields alone contributed 35% of total agricultural pollution in 2020, nearly matching drained peat soils (also 35%) and exceeding synthetic fertilizer use (23%). Of 2.5 billion tons of CO₂ equivalent from global cropland, almost half originated in East Asia and the Pacific.
The methane mechanism is well understood but rarely centered in climate discussions. When rice paddies are flooded—the traditional cultivation method across much of Asia—soil oxygen is depleted, creating anaerobic conditions where microbes break down organic matter and release methane, a greenhouse gas 80 times more potent than CO₂ over a 20-year timeframe.
That methane has always been released. What changed is the accounting. Improved measurement techniques and satellite monitoring have revealed that previous estimates significantly undercounted rice's emissions, particularly methane released during the growing season and after harvest when rice straw decomposes in flooded fields.
The solutions are not theoretical. Alternate wetting and drying (AWD)—periodically draining rice fields rather than keeping them continuously flooded—can reduce methane emissions by 30% to 70% while maintaining or even increasing yields by improving root oxygenation. The technique is not new; it has been tested and validated across Asia for two decades.
Yet adoption remains limited, constrained by water regulations, irrigation infrastructure designed for continuous flooding, and risk-averse farming cultures where rice cultivation methods have remained stable for generations. Farmers operating on thin margins cannot afford yield failures, and changing water management introduces perceived risk.
New rice varieties bred for lower methane emissions—particularly cultivars that produce less below-ground biomass for methane-generating microbes to decompose—show promise in field trials. Changing when and how rice straw is managed after harvest, rather than leaving it to decompose in flooded fields, offers another mitigation pathway.
Precision timing of fertilizer application can reduce emissions from both nitrogen use and methane production, though this requires access to soil testing and agronomic advice that many smallholder farmers lack.
The climate justice dimension is inescapable. The countries with the highest rice emissions—China, India, Bangladesh, Indonesia, Vietnam, Thailand, and Myanmar—contributed negligibly to the historical atmospheric carbon loading that has driven climate change. The United States and Europe built industrial economies on fossil fuels; Asia fed its population on rice.
Now those rice-growing nations face pressure to transform agricultural systems that have sustained civilizations for millennia, even as the wealthier countries responsible for the bulk of historical emissions resist comparably disruptive changes to their own food and energy systems.
In climate policy, as across environmental challenges, urgency must meet solutions—science demands action, but despair achieves nothing. Rice's emergence as the top agricultural emission source reflects both the scale of cultivation across Asia—where rice remains the staple food for over 3 billion people—and the reality that methane's high warming potential makes even established agricultural practices climate-significant.
The path forward cannot center on reducing rice consumption, which would translate into hunger and nutritional insecurity across much of the world. It must focus on how rice is grown: scaling proven techniques like alternate wetting and drying, accelerating research into low-emission varieties, improving straw management, and financing the transition for smallholder farmers who cannot afford the upfront costs or risks of changing methods.
The equity question extends beyond historical emissions. Wealthier nations' climate finance commitments—meant to support agricultural adaptation and mitigation in developing countries—remain chronically underfunded. Asia's rice farmers are being asked to shoulder the costs of emissions reduction without equivalent support for the agricultural transformation required.
Water infrastructure is a particular constraint. Alternate wetting and drying requires irrigation systems that allow precise field-level control—infrastructure that much of South Asia and Southeast Asia lacks. Building that capacity requires investment at scales that national governments and international climate funds have not provided.
The research clarifies that rice is not an unsolvable climate problem. It is a solvable one that requires agronomic knowledge transfer, infrastructure investment, and risk mitigation for farmers—precisely the kind of challenge that climate finance mechanisms were designed to address but have failed to adequately fund.
Rice feeds half the world. The climate challenge is ensuring it continues to do so without methane emissions that undermine the stability of the climate systems those same populations depend on. The solutions exist. The question is whether climate policy will resource them.
