Rice yields are dropping with climate change

In a new study from North Carolina State University, experts have found that rising temperatures are detrimental to rice yields. Even more recent strains of rice, which have been engineered to cope with environmental stressors like heat, are less successful in warmer conditions. 

The research was focused on the productivity of various types of rice grown on farms in the Philippines. Despite the fact that the Philippines is of the top 10 countries in global rice production, the country also imports a large amount of rice in order to meet demands. 

Study co-author Professor Roderick Rejesus said that teasing out the effects of temperature on rice yields is important to understand whether rice-breeding efforts have helped address the environmental challenges faced by modern society, including global warming.

The investigation was focused on rice yields and atmospheric conditions from 1966 to 2016 in Central Luzon, which is a major rice-growing region of the Philippines. 

“This rich dataset allowed us to see what was actually happening at the farm level, rather than only observing behavior at higher levels of aggregation like in provinces or districts,” said Professor Rejesus.

The researchers analyzed three varieties of rice planted during the 50-year study period, including traditional varieties; early modern varieties, which were bred for higher yields; and recent modern varieties that were bred for particular characteristics such as heat or pest resistance.

“Taken all together, there are two main implications here,” said Professor Rejesus. “The first is that, at the farm level, there appears to be a ‘yield gap’ between how rice performs in breeding trials and on farms, with farm performance of recent varieties bred to be more tolerant to environmental stresses not being statistically different relative to the older varieties.”

“The second is that rice breeding efforts may not have reached their full potential such that it may be possible to produce new varieties that will statistically perform better than older varieties in a farm setting.”

According to Professor Rejesus, the findings can be applied to other rice-breeding countries, like Vietnam, because the timing of the release of various rice varieties is somewhat similar to that of the Philippines.

“Plant-breeding institutions can learn from this type of analysis, too. It provides guidance as to where research funding may be allocated by policymakers to further improve the high temperature tolerance of rice varieties available to farmers.”

Professor Rejesus plans to assess other agricultural practices and innovations that affect crop yields – such as plants that can be grown during the off season to keep soils healthy – to investigate whether they can mitigate the adverse impacts of climate change.

The study is published in the American Journal of Agricultural Economics.

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By Chrissy Sexton, Earth.com Staff Writer