Climate change will increase the risk of simultaneous crop failures across the world's biggest corn-growing regions and lead to less of the nutritionally critical vegetables that health experts say people aren't getting enough of already, scientists warn.

Two new studies published Monday in Proceedings of the National Academy of Sciences look at different aspects of the global food supply but arrive at similarly worrisome conclusions that reiterate the prospects of food shocks and malnutrition with unchecked global warming. While developing tropical countries would likely be hardest hit, the destabilizing financial effects could reach all corners of the globe, the authors say.

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One paper analyzed corn—or maize—the world's most produced and traded crop, to project how climate change will affect it across the major producing regions. Much of the world's corn goes into feeding livestock and making biofuels, and swings in production can ripple through global markets, leading to price spikes and food shortages, particularly for the 800 million people living in extreme poverty.

The researchers found significant differences in corn yield depending on how high global temperatures rise.

An increase of 4 degrees Celsius—close to where the current greenhouse gas emissions trajectory would take us by the end of this century—could cut U.S. corn production by nearly half. If global warming is instead held to 2°C (the goal of the Paris climate agreement is to stay below that level) the projected loss in U.S. production would be closer to 18 percent, the researchers found.

Risk of Simultaneous Crop Failures Rises

While those numbers are pretty dramatic, the researchers find that the chances of the top-producing regions suffering extreme yield losses at the same time rises, too.

When the researchers looked at the four biggest corn exporters—the U.S., Brazil, Argentina and Ukraine—they found that the likelihood of all four suffering yield losses of 10 percent or more at the same time rises from about 7 percent at 2°C warming to 86 percent at 4°C warming.

Such simultaneous shocks in the top-producing regions, which are rare now, could have significant impacts on global markets and drive up the price of food.

"Global grain prices have been going up because of demand and biofuels," said Michelle Tigchelaar, the lead author of the study and a researcher with the University of Washington. "That has made markets tighter, so when you have a yield shock, that has really big implications for the market."

And for global stability. During the last global food crisis, in 2007 and 2008, rising costs triggered riots and unrest in countries around the world.

Vegetables also at Risk from Global Warming

The second study published Monday looked at how environmental changes brought on by climate change could impact the production and quality of vegetables and legumes—foods that government nutrition guidelines and nutritionists urge people to eat more of.

Researchers led by the London School of Hygiene & Tropical Medicine looked at 174 studies, across 40 countries, published since 1975. The authors say it is the first attempt to systematically examine how climate-induced environmental changes could impact yields of vegetables and legumes around the world.

While previous research has shown that increased levels of carbon dioxide could boost some vegetable and legume yields, the new study finds that any benefits will be offset by the negative effects of increased ozone, less water availability and increased salinity.

Nutritionally important vegetables and legumes can be particularly sensitive to temperature increases and more vulnerable to heat stress than staple or cereal crops. The researchers found that without efforts to reduce emissions, a lack of water and increased ozone would cut yields of vegetables by about 35 percent in the second half of this century.

Result: People Lose Key Sources of Nutrition

Globally, about 2 billion people suffer from micronutrient deficiencies linked to a lack of vegetable and legume consumption, while worldwide per capita consumption of vegetables and fruits is between 20 and 50 percent below recommended levels.

"Vegetables and legumes are vital components of a healthy, balanced and sustainable diet and nutritional guidelines consistently advise people to incorporate more vegetables and legumes into their diet," said Pauline Scheelbeek, the lead author of the study. "Our new analysis suggests, however, that this advice conflicts with the potential impacts of environmental changes that will decrease the availability of these important crops unless action is taken."

Another recent study that analyzed the impact of climate change on rice, a primary food source for 2 billion people, found that rising carbon dioxide levels will also diminish its nutrient levels.