Report shows increase in rice paddy greenhouse gas emissions and how mitigation strategies can be achieved without reducing global food production
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Feeding more than half the world’s population, rice farming is intensifying worldwide. This makes understanding its impact on greenhouse gas emissions and how to reduce them without threatening food security all the more important.
Since the 1960s, greenhouse gas emissions from rice paddies have doubled to approximately 1.1 billion tons of CO2 annually, according to a study led by Boston College scientists.
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Methane is a major greenhouse gas contributor from rice paddies, which is significant because it drives near-term warming.
The recent study provides an extensive global assessment of rice-related greenhouse gas emissions, covering methane, nitrous oxide, and soil carbon changes from 1961 to 2020.
‘Our goal was to understand the full climate impact of rice systems – not just methane, but all major greenhouse gases together – and to identify realistic pathways for mitigation,’ said Boston College Professor of Earth and Environmental Sciences, and the lead author of the report, Hanqin Tian.
The researchers combined machine learning based on more than 21,000 field observations and a global meta-analysis. These approaches allowed the team to quantify total emissions, identify key drivers such as land expansion and residue management, and evaluate how future mitigation strategies could contribute to climate targets, including methane reduction goals.
The research team identified two dominant drivers behind the surge in emissions over six decades: the expansion of rice cultivation, especially in developing regions, and the intensified incorporation of crop residues, which are returned to flooded soils, stimulating methane production.
Regionally, East Asia experienced renewed methane emissions linked to heavy straw incorporation. This is when excessive amounts of the remaining rice straw are returned to the soil after harvest rather than removed. The process improves soil fertility and increases organic matter in the soil, which, in its inevitable decomposition, produces methane emissions. The practice of returning straw to the soil is responsible for 18 per cent of rice’s increase in overall net emissions since the 1960s.
In addition, Africa emerged as a fast-growing emissions hotspot as the area under rice cultivation increased sevenfold on average between 1961 and 2024, reaching 40 million acres.
Additionally, fertiliser is a major contributor to emissions. Synthetic nitrogen usage increased by about 76 per cent after 2000. This leads to the emission of larger amounts of nitrous oxide.
Despite rising emissions, the study prompts a clear opportunity: improved farm management could reduce emissions by about 10 per cent without compromising yields. Key strategies include optimising water management to reduce methane formation, minimising excessive residue return to soils, and improving the efficiency of nitrogen fertiliser.
‘These are practical, scalable solutions that farmers can adopt today,’ said Boston College Associate Professor of Engineering and the study’s co-author, Susan Pan. ’They offer a meaningful pathway for agriculture to contribute to near-term climate targets, including methane reduction goals.’
