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Staple foods like wheat, beans, and other legumes could struggle in the coming years — which will have far-reaching public health consequences
This story was originally published on Civil Eats.
As the climate crisis progresses, the planet is becoming less inhabitable — not only for humans and other animals, but also for plants.
Farmers know first-hand how climate disasters, pollinator loss, heat waves, flash floods, and diminishing water supplies can make growing crops harder and less predictable. Yet many questions remain when it comes to how exactly crops are responding across cultivars and varying landscapes.
A new review paper, published in Advances in Nutrition, draws together the existing science of how climate change threatens staple grains, fruits, vegetables, and nuts across the world, while also underscoring the significant need for further research. The team of public health researchers from John Hopkins Bloomberg School of Public Health and the Children’s Investment Fund Foundation in London conclude that climate change — including the combined impacts of rising temperature and carbon dioxide, rising sea levels, and climate disasters — will cause crop yields, or the amount of food we can produce on the planet, to fall. The authors project that this could trigger increased spikes in food prices, deepening food insecurity and micronutrient deficiencies.
“The paper shows very clearly that production will definitely be diminished,” said Martin Bloem, the director of the Johns Hopkins Center for a Livable Future and an author on the review. The researchers found that foods rich in micronutrients — particularly vitamin A, zinc, and iron — will see decreased yields, especially threatening the staple food and nutrient supply of low- and middle-income countries. While unable to draw more nuanced conclusions, Bloem says “there’s enough evidence that we need to [turn to] solutions.”
Climate change could wreak havoc on staple crops — which will have far-reaching public health consequences.
Already, over 2 billion people, or 30 percent of the global population, suffer from micronutrient deficiencies, a major cause of death and disease, and the authors project this will likely worsen.
Richard Semba, the review’s lead author and a professor at the School of Public Health, hopes the paper will draw attention to this urgent but often overlooked aspect of the climate crisis.
“We’re watching this disaster unfold,” he said. “People who work in international health and nutrition need to start pointing out the changes that are going to come with rising temperature, atmospheric carbon dioxide, and sea level rise.”
This growing health burden is an environmental justice issue, given that it will not be shouldered equally throughout the world. “The countries that are likely to feel the brunt of this, like with so many of the consequences of climate change, are those in the developing world — those that are already on the brink of nutritional deficiency and rely most heavily on the foods affected by this,” said Matthew Smith, a research scientist at the Harvard T.H. Chan School of Public Health. “That’s a huge part of the story.”
The potential for micronutrient deficiencies comes with far-reaching public health consequences, explains Smith. “Zinc deficiency, especially in children, makes you a lot more susceptible to severe cases or dying from respiratory infections, diarrheal diseases, [and malaria],” said Smith, who wasn’t involved in the paper. Iron deficiency, he explained, “can cause anemia, lower IQ and cognitive ability, reduce work capacity, and increase mortality for mothers and their children.”
Both iron and zinc are found in legumes, nuts, and grains, which the authors expect will see critical drops in yields. Rice, a staple crop for 3.5 billion people, is increasingly threatened by coastal erosion and rising temperatures. Climate change is predicted to bring major drought to over 60 percent of areas that grow wheat, another important source of nutrition and energy. As the review notes, beans, grown by smallholders in western Malawi, northern Mozambique, Zambia, Zimbabwe, and Tanzania will likely no longer be cultivated in the region by 2050, due to worsening drought.
The review also looked at vitamin A, commonly found in leafy green vegetables and yellow and orange fruit. Like zinc, vitamin A is important for immunity and decreasing the risk of infections; a deficiency can also lead to vision problems, including night blindness. The authors highlight how mangos, an important source of vitamin A, are sensitive to shifts in rainfall and temperature. In some countries, their cultivation is already moving to higher elevations and latitudes, more conducive to their growth and flowering, to adapt to climate change.
The Research Is Just Beginning
While the authors project overall production declines, they provide far from a complete picture of how climate change disrupts crop growth. In researching the paper, Semba says he was surprised by the “considerable lack of standardization” across studies and consistent data needed for more nuanced conclusions. “Luckily, there were enough studies done where you could paint broad strokes,” he added.
The authors are hopeful that the review will help serve as a jumping off point for more detailed research. “There are so many gaps,” said Bloem. “I do feel that the paper is just the beginning of a whole series of papers, looking at different gaps.”
One murky area is the existing body of research on how micronutrient levels within individual plants are affected by rising temperatures and atmospheric carbon dioxide. Many of the studies from the past 30 years were conducted with a technology known as Free-Air Carbon Dioxide Enrichment (FACE), which was developed to study how plants respond to more carbon dioxide in an open-setting under natural conditions and doesn’t account for rising average temperatures. But the review also brings in emerging studies that rely on a new technology, known as T-FACE, which combines the existing FACE set-up with infrared heaters to allow scientists to study warmer temperature and carbon dioxide levels at the same time.
When rising carbon dioxide is studied on its own, the results show that plant growth tends to be stimulated. Yet the review notes that this fast growth often leads to lowered concentrations of micronutrients in the plants. However, when rising temperature and elevated carbon dioxide are looked at together in T-FACE studies, some initial data suggests that the micronutrient levels in individual plants remain high even as yields go down. And that decrease in crop yields, the paper’s authors say, will likely be the most significant threat to micronutrient access.
In addition, climate impacts such as extreme weather events are wiping out entire fields, lowering yields, and disrupting the food supply chain, while ground-level ozone pollution (which gets worse when the temperature rises) is already diminishing the growth of staples, like rice, wheat, soybean, and potatoes. Rising oceans are eroding and inundating coastal farm ecosystems. And climate change is one of the factors driving the decline in pollinators, which are essential for many crops.
Experts unaffiliated with the review paper also emphasized that T-FACE technology is still in its infancy with limited data.
“The number of studies that needed to be assembled in order to find a consistent signal for strict FACE experiments was quite a few,” said Harvard’s Matthew Smith. “If you look at the review’s studies, there’s [only] a handful that have used T-FACE to find results. But often they’re either looking at a single cultivar or under a single growing season.”
Based on the recent addition of T-FACE research, Smith is not ready to draw any firm conclusions just yet. However...