Climate change is cutting deeply into yields from so-called Miracle Rice, which is credited with keeping millions from starvation across Asia, according to Dr Shaobing Peng, a research scientist with the International Rice Research Institute in Los Banos, Philippines.

Yields from IR8, which was developed in the 1960s by the IRRI, have dropped by about 15 percent, according to a research team led by Dr Peng whose study was printed in the current edition of Field Crops Research.

IR8, when it was first developed, produced 9.5 to 10.5 metric tons of rice per hectare at a time when average global rice yields were only around 2 tons per hectare. However, according to Dr Peng's paper, IR8 yields have dropped to about 7 tons per hectare, primarily because nights have become hotter.

"IR8 still performs very well considering that global average yields still hover around 4 tons per hectare," Dr Peng said in a printed release from the IRRI. However, he said, "Hotter nights, which are known to reduce rice yields, and other environmental changes such as modifications in soil properties from maintaining the soil under flooded conditions and air pollution are all possible contributing factors."

The findings, according to the paper published in Field Crops Research, "suggest that the low yield of IR8 resulted from the lack of adaptation to changed environmental conditions, and maintenance breeding plays a critical role in improving adaptation of newly developed varieties to environmental changes that have a negative impact on older varieties. Our study provides strong justification for continuous maintenance breeding efforts to preserve rice yield potential through improved resistance to rapidly evolving biotic and abiotic stresses."

Dr. Peng's study advocates the importance of continuing research into hybrid rice varieties. Other studies show that more than 57 percent of China's rice crop is composed of hybrid rice, with Chinese farmers now planting hybrid rice on around 17 million hectares annually—more than half of the country's total rice area of around 29 million hectares, according to the IRRI. That has boosted the country's rice yields to more than 6 tons per hectare. Continuing "maintenance" breeding of different hybrid varieties is crucial because it allows to cope with the changing environment.

Nor are warmer nights the only cause for concern. According to a study titled Strategies for Adaption to Sea Level Rise by the United States Environmental Protection Agency, if global climate change raises sea level as much as one meter over the next century, as climate scientists have predicted, hundreds of thousands of square kilometers of coastal wetlands and other lowlands could be inundated.

Although the Intergovernmental Panel on Climate Change has concluded that has forecast that climate change will raise sea levels by 18-59 cm (0.6-1.9 feet), the Proudman Oceanographic Laboratory in the UK, using what they describe as a newer and more accurate reconstruction of sea levels over the past two millennia, have more than doubled that to 0.8-1.5 meters, closer to what the EPA is predicting. That would put vast amounts of rice land under sea water.

"Beaches could retreat as much as a few hundred meters and protective structures may be breached. Flooding would threaten lives, agriculture, livestock, buildings and infrastructures. Salt water would advance landward into aquifers and up estuaries, threatening water supplies, ecosystems and agriculture in some areas," the EPA study noted.

Eight to ten million people live within a meter of high tide in each of the unprotected river deltas of Bangladesh, Egypt and Vietnam – three of the most important rice-growing areas in the world. In Vietnam, for instance, the most fertile agricultural lands, together with half of the population, live in the low-lying Red and Mekong River Deltas.

"Even in nations that are not, on the whole, particularly vulnerable to sea level rise, some areas could be seriously threatened. Examples include Sydney, Shanghai, coastal Louisiana and other areas economically dependent on fisheries or sensitive to changes in estuarine habitats," the EPA report found. "As a result of present population growth and development, coastal areas worldwide are under increasing stress. In addition, increased exploitation of non-renewable resources is degrading the functions and values of coastal zones in many parts of the world. Consequently, populated coastal areas are becoming more and more vulnerable to sea level rise and other impacts of climate change. Even a small rise in sea level could have serious adverse effects."

Added to this are concerns that climate change will increase storm severity. In 2007 and 2008, two storms – Tropical Storms Sidr and Nargis – rose in the Bay of Bengal and slammed into Bangladesh and Burma respectively. With winds peaking at 260 kilometers an hour, Sidr hit Bangladesh with sustained winds of 215 km/h, killing at least 3,447 and perhaps many more and reducing Bangladesh's annual rice harvest by 1.4 million to 2 million metric tons. That required the government to import up to 3.5 million tons over its normal shortfall of 2 to 2.4 million. Then, in May of 2008, Nargis hit the Irrawaddy River Delta, becoming the most destructive natural disaster in Burma's history, killing as many as 130,000 and ruining at least 200,000 hectares of the Irrawaddy Delta for planting in 2008. It is believed it created a rice shortfall in Burma of 1.5 million tons although government statistics are scanty.