Rice provides the staple food for around 2 billion people, and demand is forecast to grow at 1% a year, with no increase in land available. Some recent studies have indicated that rice production is contributing to climate change through emissions of greenhouse gases (GHG). An analysis by Reiner Wassmann, Klaus Butterbach-Bahl and Achim Dobermann suggests that the impact is complex and it is crucial that the interactions between production and climate change and the potential to mitigate negative effects are explored.
Wassmann and colleagues, based at the Institute for Meteorology and Climate Research in Karlsruhe, Germany and the International Rice Research Institute , Manila, Philippines say that changing trends in crop management mean that methane emissions will be lower from rice crops, but there will be increased nitrous oxide (N2O). A move to upland conditions is likely to mean losses in soil organic carbon that translate into carbon dioxide (CO2) emissions, they say in a paper in CAB Reviews.
In terms of the effect of climate change on rice, increasing temperatures may lead to spikelet sterility in rice, but the impacts of increased CO2 on rice productivity are unclear.
Wassmann and his co-writers argue that there are several ways to limit emissions of greenhouse gases and to respond to the impacts of climate change on rice production. These include producing high-yielding plants so that less debris is turned into methane, and plants better able to make use of CO2 and survive heat. The team also suggest fertiliser management could be adapted so that N input is better used by the plant, with less N2O being released. Better water management has potential to reduce methane emission. Another major opportunity is using rice crop residues for renewable energy, particularly if efficient ways of obtaining ethanol from rice straw can be achieved. They believe that there is potential to reconcile low emissions and high production levels while responding to changing socio-economic and environmental conditions.
Wassmann and colleagues say that, while no other crop has been studied as intensively as rice with regard to GHG emissions "vital information on the interactive nature of different GHGs is still lacking, which limits the reliability of projections of GHGs as well as mitigation recommendations."
The paper, "Irrigated rice production systems and greenhouse gas emissions: crop and residue management trends, climate change impacts and mitigation strategies" by Reiner Wassmann, Klaus Butterbach-Bahl and Achim Dobermann appears in CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources (2007) 2, No. 004.