C&B Notes

Optimizing Rice Would Be Nice

Rice is the most important staple in the world’s diet.  Past cultivation advances have eliminated hunger in many corners of the globe, and current development efforts are focused on creating varieties particularly suited to the demands of certain sub-climates.  For example, optimizing seeds for rainwater-dependent fields that are susceptible to droughts and/or floods could greatly reduce weather-driven yield variability that can now destroy a whole season’s worth of crops.

A seed of rice that could transform the developing world saved Asha Ram Pal’s farm in the Indian state of Uttar Pradesh in the summer of 2008.  Mr Pal had planted rice on his small plot, not much bigger than a football field.  Floods are an ever-present threat in the state, making it one of the poorest places in the world.  And that year the monsoon was particularly heavy, remembers Bob Zeigler, director of the International Rice Research Institute (IRRI).  Mr. Pal’s fields flooded for two weeks after he planted the rice seedlings; a few weeks later, they were inundated again.  He thought his crop was lost.  His neighbors advised him to do what they have always done when the floods come: prepare for hunger.

But this time Mr. Pal had planted an experimental seed developed by scientists from IRRI in the Philippines.  The seed has a genetic sequence bred into it which puts it into a sort of suspended animation when submerged.  Instead of drowning, Mr. Pal’s rice sprang back when the water receded.  In a normal year he gets a tonne or so from his 1-hectare (2.5-acre) plot; in a bad year nothing. In that terrible flooded season, he harvested 4.5 tonnes — as good a yield as on any rain-fed paddy in the world.

Flood-resistant rice is now spreading as fast as the waters themselves.  Five years after the first field trials, 5m farmers across the world are planting more than a dozen varieties of rice with flood-resistant genes, collectively called “Sub 1”.  They are proliferating even faster than new rice varieties during the heady early days of the first green revolution in the 1960s.  “And Sub 1 is the first of a new generation of seeds,” says Mr. Zeigler.  If all goes well, over the next few years plants that tolerate drought, salinity and extreme heat will revolutionize the cultivation of mankind’s most important source of calories…

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As a rule of thumb, if the world’s population grows by 1 billion, an extra 100m tonnes of rice is required to feed them.  Given current world-population forecasts, total rice consumption, now under 450m tonnes, is likely to grow to 500m tonnes a year by 2020 and to 555m by 2035 — an increase of 1.2-1.5% a year.  That would be manageable if rice yields were also growing at that rate.  But they are not.  They are rising at barely half that pace.

The first green revolution almost doubled yields from 1.9 tonnes a hectare in 1950-64 to 3.5 tonnes in 1985-98.  Even that was only enough to keep pace with population growth: yields and population rose at the same rate (1.75% a year) in the half century after the green revolution started.  Now the gains seem to have levelled off.  Plant breeders fear that, with current technology, ten tonnes a hectare for rice in intensive-farming systems may be the limit, though it is not clear why. What is clear is that, out in the fields, output per hectare is stalling, and in some places falling.  For 25 years, IRRI has been planting a field using its best seeds.  The field itself has remained much the same: the bugs and microbes that live in the roots of the rice plant mean that soil fertility is maintained even if three crops are grown each year.  But output from the plot has fallen from nine to ten tonnes a hectare in the early 1990s to seven to eight tonnes now, as pests and diseases have taken their toll.  Rice yields were rising at 2.5% a year between 1962 and 1982.  But between 1992 and 2012 growth fell to just 0.8% a year…

So a lot is riding on boosting rice yields.  But how likely is it that a second green revolution will take off?  The first was a relatively simple affair, technologically at least.  Conventional rice varieties were long and leggy.  If you gave them fertilizer, they grew too tall and fell over.  That changed in 1962, when IRRI released a dwarf variety called IR8.  Because its stem was short, it was able to absorb fertilizer without collapsing.  So now farmers had a crop they could feed.  And with stem growth restricted, more of the increase in plant size went into the head of seeds (called a panicle).  IR8 spread from the Punjab to the Philippines, transforming farming wherever water could be controlled and fertilizer delivered.

The second revolution will be different.  Farmers will not adopt a single miracle variety.  Instead, researchers will tailor seeds for particular environments (dry, flooded, salty and so on).  And they are also trying to boost the nutritional quality of rice, not just the number of calories.  As a result, the second revolution will be felt most profoundly in the poorest areas and among the poorest farmers. In contrast, the first had the biggest impact in the richest fields, with the most water and fertilizer.

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China’s experience shows that a series of small improvements can add up to something large.  This will be true of the second revolution on the poorest lands.  The first green revolution had most impact on irrigated land and, thanks to it, the 80m hectares which are irrigated (an area equivalent to Vietnam, Laos and Cambodia put together) now have yields of five to six tonnes a hectare; they produce three-quarters of the world’s rice.  But there is nearly as much rice land which depends on rainwater.  Yields there are far lower — between one and two and a half tonnes a hectare — and rain-fed lands produce only a quarter of the world’s rice.  Yields are low because almost half this land is prone to drought and a third to floods.  Most African paddies fall into this category, which is why the first green revolution passed Africa by.

Drought- and flood-tolerant seeds could double yields from these areas.  That would boost harvests from 110m tonnes to 220m, and push global output to 550m tonnes — enough to meet expected demand in 2035.  In short, all the extra rice could come from rain-fed areas alone.

Because yields on rain-fed lands are low, even a doubling would not increase total production by as much as the first green revolution did.  But the impact on poverty would be greater.  More than 500m of the absolute poor (those with $1.25 a day or less) depend on rice, far more than on any other food (see chart 2).  A disproportionate number of them live in north-east India, Bangladesh and the Irrawaddy delta of Myanmar. In these areas the lowest castes and tribes have been forced onto the worst lands.

Those are the very places where the second green revolution would make the biggest impact.  Flood-resistant rice “differentially benefits [India’s] scheduled castes and tribes”, a recent study of one of the early field trials concludes.  If these improvements were combined with another program to boost the nutritional quality of rice — the so-called Golden Rice project which genetically modifies rice to include additional vitamin A — then the benefits to some of the poorest people in the world would be vast.