It was climate change, thousands of years ago, that helped rice spread everywhere. And it is climate change, which is happening right now, that poses a serious threat to numerous rice crops.
Around 3.5 billion people, or half of the planet's population, depend on rice as a staple crop, especially in Asia. First cultivated around 9,000 years ago in China's Yangtze Valley, rice would spread through East, Southeast, and South Asia, and from there to the Middle East, Africa, Europe, and America.
Along the way a growing variety of cultivars emerged, better adapted to local environments.
In a new study, researchers at New York University's Center for Genomics and Systems Biology have mapped the routes rice took over time in Asia by sequencing the genomes of more than 1,400 varieties of rice plants at the same time. that explore geographic, archaeological, and historical climate data.
"During the first 4,000 years of its history, rice cultivation was largely confined to China, and the cultivated subspecies japonica (a major variety of rice) was the one that was grown," they explain.
“Then a global cooling event 4,200 years ago, also known as the 4.2k event, believed to have had widespread consequences, including the collapse of civilizations from Mesopotamia to China, coincided with the diversification of japonica rice into temperate varieties and tropical ”.
"The newly evolved temperate varieties spread to northern China, Korea and Japan, while the tropical varieties spread to Southeast Asia."
In other words, global cooling precipitated the emergence of new varieties of rice and the relentless spread of the crop in both North and South Asia.
Now, another global climate phenomenon, this time warming, will present increasing challenges to rice cultivation, weakening the food security of millions of people. Warming temperatures could positively affect rice production in some colder areas, such as northern China, but not so much in already warm, much less hot and humid areas further south.
“Rice cultivation extends from drylands to wetlands and from the banks of the Amur River at 53 ° north latitude to central Argentina at 40 ° south latitude. Rice is also grown in cold climates at altitudes of more than 2,600 m above sea level in the mountains of Nepal, as well as in the hot deserts of Egypt, "explains the Food and Agriculture Organization of the United Nations. .
“However, most of the annual rice production comes from tropical climate zones,” adds FAO. “In 2004, more than 75 percent of the world's harvested rice area (about 114 million out of 153 million hectares) came from the tropical region whose boundaries are formed by the Tropic of Cancer in the Northern Hemisphere and the Tropic of Capricorn in the South Hemisphere ”.
In these tropical areas, rising temperatures pose challenges by worsening droughts, which will imply an even greater demand for already scarce freshwater sources. As a result, by mid-century rice yields could drop significantly in South Asia, Southeast Asia, East Asia, and sub-Saharan Africa. At the same level with diminishing returns, the price of rice will rise, affecting poor people in Asia, Africa and elsewhere.
The current COVID-19 pandemic provides a preview of what is to come. Extensive blockades in many major rice-producing nations have seen rice production rates decline and prices rise, while there have been major disruptions in international rice trade with producing nations that store the rice rather than sell it.
"The panic buying caused rice exporting countries to impose limits or bans on exports, while the maximum domestic prices imposed by some importing countries have led to a reduction in import volumes," UN Environment notes. “Along with logistical stoppages resulting from nationwide blockades, more than half of the world's rice supply, originating from five key countries, is now at risk. Currently, price surges disproportionately hurt the poorest households for whom rice is a staple food and where rice can account for almost half of monthly spending.
Climate change may make a similar scenario a permanent feature of the future, warns Wyn Ellis, executive director of the Sustainable Rice Platform. "The adversities in the rice trade unleashed by COVID-19 are a sharp anticipation of what climate change has in store," says Ellis.
"But instead of a temporary threat to farmers and food value chains, the impacts of climate change will be long-lasting, probably for generations," adds the expert. "This pandemic shows us how devastating the consequences of inaction can be and how climate change can intensify existing crises."