The climate is changing. Overwhelming scientific research and evidence have shown this to be the case. While there is still ongoing scientific exploration into climate change, IRRI recognizes two universal trends predicted by all climate change models:
- Temperatures will increase, resulting in more heat stress and rising sea levels, and
- There will be more frequent and severe climate extremes.
Rice plays a central role in feeding more than 3 billion people, including most of the world’s 1 billion poor, and any significant negative effect on rice production caused by climate change would be devastating for efforts to achieve global food security and address poverty.
Climate change may have a positive impact on rice production in some areas. For example, a global temperature rise might allow more rice production to occur in the northern regions of countries such as China, or growing two rice crops where, until now, only one can be grown per year. Yet, the vast majority of climate change impacts and the overall impact of climate change on rice are likely to be negative.
An International Food Policy Research Institute (IFPRI) study forecasts a 15% decrease in irrigated rice yields in developing countries and a 12% increase in rice prices as a result of climate change by 2050.
The impact of climate change on rice
Recent predictions suggest that, as a consequence of melting polar ice shields and glaciers and rising temperatures, seawater levels may rise on average by about 1 m by the end of the 21st century.
Rice is grown in vast low-lying deltas and coastal areas in Asia predicted to experience the brunt of sea-level rises – making rice one of the crops most vulnerable to climate change. For example, in Vietnam, more than 50% of rice production is grown in the Mekong River delta – all of which would be affected by sea-level rises.
Predicting the precise effect of sea-level rises on rice production in these areas is complicated because the effect goes beyond the basic sea-level rise itself. The entire hydrology of the delta would be affected, including changes in sediment discharge and shoreline gradients.
Rice is unique in that it can thrive in wet conditions where other crops fail. Uncontrolled flooding is a problem, however, because rice cannot survive if submerged under water for long periods of time. Flooding caused by sea-level rises in coastal areas and the predicted increased intensity of tropical storms with climate change will likely hinder rice production. At present, about 20 million hectares of the world’s rice-growing area is at risk of occasionally being flooded to submergence level, particularly in major rice-producing countries such as India and Bangladesh.
Major flooding events are likely to increase in frequency with the onslaught of climate change and rice-growing areas, currently not exposed to flooding, will experience floods.
Salinity is also associated with higher sea levels as this will bring saline water further inland and expose more rice-growing areas to salty conditions. Rice is only moderately tolerant of salt and yields can be reduced when salinity is present.
As with sea-level rises, the effects of salinity can permeate throughout whole deltas and fundamentally change hydrological systems.
Increased carbon dioxide levels and higher temperatures
Increases in both carbon dioxide levels and temperature will also affect rice production. Higher carbon dioxide levels typically increase biomass production, but not necessarily yield. Higher temperatures can decrease rice yields as they can make rice flowers sterile, meaning no grain is produced. Higher respiration losses linked to higher temperatures also make rice less productive.
The different predictions for elevated temperature, carbon dioxide levels, changes in humidity, and the interactions of these factors make forecasting future rice yields under these conditions challenging. IRRI research indicates that a rise in nighttime temperature by 1 degree Celsius may reduce rice yields by about 10%.