Climate Change to Hit Crops Faster Than Expected, New Model Warns

New projections see maize losing ground faster as 2100 approaches and the Middle East may face climate impact on crops decades earlier. But wheat is expected to thrive

Ruth Schuster
Ruth Schuster
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Stunted ears of wheat in a drought-hit region in southern Ukraine.
Stunted ears of wheat in a drought-hit region in southern Ukraine.Credit: REUTERS
Ruth Schuster
Ruth Schuster

Climate change is going to impact crops faster than had been thought, according to new models. In fact, the latest models predict changes emerging as soon as 2040 in some areas.

By the year 2100, the global maize crop could diminish by a quarter as some 75 percent of the land on which it is grown is impacted by climate change, according to the new generation of models published Monday in Nature Food.

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Wheat, on the other hand, is expected to thrive under warmer weather and more carbon dioxide, all other things being equal.

Bless wheat but according to the new projections, negative climate impacts may consistently emerge before the year 2040 in several key producing regions, including the Middle East, the international team writes.

While stressing the uncertainties, which are many and legion, the team deems it appropriate to warn: “These results suggest that major breadbasket regions will face distinct anthropogenic climatic risks sooner than previously anticipated.”

Projecting crop yields on a changing planet is insanely complicated and is far short of consensus. However, since the last round of modeling, the case of maize (down) and wheat (up) has become clearer. The case of soybeans and rice is foggier but, in any case, the range anticipated for soybeans and rice is lower than it had been in the latest set of modeling.

The previous projections were based on Phase 5 of the Coupled Model which considers both climate models and crop models. The new projections are based on Phase 6 of these models.

On a hotter planet

The warming the planet is experiencing isn’t uniform. The global mean increase so far is +1.1 to 1.2 degrees Celsius, but Israel has already experienced an increase of 1.5 degrees, and the far north about 3 degrees. Leaving extremes such as scorching heat waves and freezing cold snaps out of it, many plants have been stimulated by the warmth (so far) and the heightened atmospheric carbon dioxide (ditto). Wheat, for instance, loves it; maize is more ambivalent.

Like us, plants have optimal ranges of conditions and scientists had been predicting a downturn in agricultural yields by 2100.

The Phase 5 model had suggested maize yields might even creep up toward end-of-century (2069-2099). The Phase 6 model anticipates maize productivity falling by 6 percent under the best-case emissions scenario  involving strong mitigation efforts, and by 24 percent under the worst-case scenario, by the year 2100.

Corn harvested on a Venezuelan farm this month.Credit: FEDERICO PARRA - AFP

Wheat is anticipated to produce 9 percent more in the best-case emissions scenario (rather than 5 percent as previously expected), to 18 percent in the worst case. Yes, the hotter and more carbon dioxide there is, the happier wheat will be, up to a point. Also, it is expected to be grown farther north than it is today.

Why the difference between maize and wheat? Maize derives less benefit than wheat from heightened CO2 and is grown in southern latitudes where some places are already approaching crop-limiting temperatures, the team explains.

Also, by the year 2100, in the best-case scenario around 10 percent of the areas where maize is grown now will be feeling the impact of climate change. In the worst-case scenario, the figure is 74 percent.

The carbon dioxide lag

What changed in the new model? One thing is that the projection for atmospheric carbon dioxide concentration in the year 2099 was raised from 927 parts per million (a horrifying level) to 1,122 parts per million. The preindustrial CO2 concentration was about 278 ppm. In 2020 it reached 413.2 ppm, according to the World Meteorological Organization: never before has the CO2 level risen this fast in planetary history, insofar as we know.

By the way, no, the coronavirus pandemic did not slow emissions growth. Indeed, for all the lockdowns and declarations by the nations, global emissions are still increasing.

“As long as emissions continue, global temperature will continue to rise,” the WMO says. But even if we were to halt all greenhouse gas emissions this second and never emit another molecule of methane or CO2 or the others, more temperature and sea level increases are inevitable because both react to increases in atmospheric CO2 at a lag.

Correlation between atmospheric carbon dioxide, temperature - and sea levelsCredit: John Englander / National Academy

“At the current rate of increase in greenhouse gas concentrations, we will see a temperature increase by the end of this century far in excess of the Paris Agreement targets of 1.5 to 2 degrees Celsius above preindustrial levels,” said WMO Secretary-General Prof. Petteri Taalas last month. “We are way off track.”

Actually, the signal of climate change is already starting to emerge in agriculture out of the statistical noise in some areas.

In the future, crop models indicate that even under the best-case scenario, maize will be impacted by global warming before 2040 in the Middle East, western United States, Central Asia, southern Europe and tropical South America.

As for wheat, to be accurate the new model predicts it will be happy in large parts of the areas where it is grown today, though not all. That too will happen faster than we thought, in some places.

As for the soybean yields of enigmatic future: the legume is expected to suffer, from some point, in its main cultivation areas of the U.S., Brazil and Southeast Asia, but to experience significant gains across China and generally higher latitudes, hence the uncertainty in forecasting its yields in 2100 as the weather warms. And it is warming.

Soybeans in a field in Roachdale, Indiana, U.S.Credit: Bryan Woolston/REUTERS

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