Rice cultivation鈥檚 climate costs
Rice paddy greenhouse gas emissions聽have doubled during the past 60 years鈥攂ut practical farm changes could cut聽methane emission and support global climate targets without reducing food聽production, a team led by Boston College scientists in the journal聽Nature Food.
Rice feeds more than half the world's population, but has a growing climate聽footprint. Flooded paddies emit methane and nitrous oxide, two powerful聽greenhouse gases. As rice farming intensifies worldwide, understanding its聽methane footprint鈥攁nd how to reduce it without threatening food聽security鈥攈as become a global priority.
鈥淥ur goal was to understand the full climate impact of rice systems鈥攏ot just聽methane, but all major greenhouse gases together鈥攁nd to identify realistic聽pathways for mitigation,鈥� said Boston College Professor of Earth and聽Environmental Sciences Hanqin Tian, lead author of the report and director聽of the Center for Earth System Science and Global Sustainability at the聽Schiller Institute for Integrated Science and Society.
Professor Hanqin Tian (Lee Pellegrini)
Since the 1960s, greenhouse gas emissions from rice paddies have doubled聽to approximately the equivalent of 1.1 billion tons of carbon dioxide聽annually, the researchers report. Methane is a major contributor, particularly聽in regions such as East Asia, while Africa is emerging as a new hotspot due聽to expanding rice cultivation, according to the study.
Methane is especially important because it drives near-term warming,聽making it a central focus of global climate efforts such as the Global Methane聽Pledge, which aims to cut methane emissions by at least 30 percent this聽decade, said Tian, who also directs the Global Carbon Project鈥檚 Boston聽Office.
This study provides the most comprehensive global assessment of rice-related greenhouse gas emissions to date, covering methane, nitrous oxide,聽and soil carbon changes from 1961 to 2020, Tian said.
Annual global rice cultivation ranged from 397.4 million acres in 2015 to 426聽million acres in 2024. In Africa, rice cultivation acreage increased seven-fold聽between 1961 and 2024, to 40 million acres.
The researchers combined machine learning trained on more than 21,000 field observations, a process-based ecosystem model, and a global meta-analysis. By integrating these approaches, Tian said the team quantified聽total emissions, identified key drivers such as land expansion and residue聽management, and evaluated how future mitigation strategies could聽contribute to climate targets鈥攊ncluding methane reduction goals under聽international initiatives.
Tian said the team wanted to quantify the role rice paddy cultivation plays in聽global greenhouse gas emissions鈥攅specially methane鈥攁nd the factors聽driving their rapid increase. Just as crucial was understanding how emissions聽can be reduced through realistic changes in farming practices, and the聽potential for reductions to contribute to climate goals set by entities such as聽the Global Methane Pledge, which counts 159 participating countries.
Tian and colleagues from Alcorn State University, Auburn University,聽Stanford University, University of Maryland, and France's University of聽Versailles Saint-Quentin-en-Yvelines identified two dominant drivers behind聽the six-decade surge in emissions:
- Expansion of rice cultivation, particularly in developing regions, which聽has increased total emissions globally
- Intensified residue incorporation, where crop residues are returned to聽flooded soils, boosting methane production聽
Regionally, East Asia experienced renewed methane increases linked to聽heavy straw incorporation, while Africa emerged as a fast-growing emissions聽hotspot as rice cultivation acreage increased seven-fold between 1961 and聽2024, to 40 million acres, Tian said.
Despite rising emissions, the study highlights a clear opportunity: improved聽farm management could reduce emissions by about 10 percent without聽compromising yields. Key strategies include: optimizing water management聽to reduce methane formation, reducing excessive residue return to soils, and聽improving nitrogen fertilizer efficiency.
鈥淭hese are practical, scalable solutions that farmers can adopt today,鈥� said聽study co-author and Boston College Associate Professor of Engineering聽Susan Pan, research director at the Center for Earth System Science and聽Global Sustainability. 鈥淭hey offer a meaningful pathway for agriculture to聽contribute to near-term climate targets, including methane reduction goals.鈥�