How Climate Change could make our food less nutritious

Rising carbon levels in the atmosphere can make plants grow faster, but there's another hidden consequence: they rob plants of the nutrients and vitamins we need to survive. In a talk about global food security, epidemiologist Kristie Ebi explores the potentially massive health consequences of this growing nutrition crisis -- and explores the steps we can take to ensure all people have access to safe, healthy food.

Yogi Berra, a US baseball player and philosopher, said, "If we don't know where we're going, we might not get there." Accumulating scientific knowledge is giving us greater insights, greater clarity, into what our future might look like in a changing climate and what that could mean for our health. We’re going to talk about a related aspect, on how our emissions of greenhouse gases from the burning of fossil fuels is reducing the nutritional quality of our food. 

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We'll start with the food pyramid. We all need to eat a balanced diet -- we need to get proteins, we need to get micronutrients, we need to get vitamins. This is a way for us to think about how to make sure we get what we need every day, so we can grow and thrive. 

But we eat not just because we need to, we also eat for enjoyment. Bread, pasta, pizza -- there's a whole range of foods that are culturally important. We enjoy eating these; they're important for our diet, but they're also important for our cultures. 

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Carbon dioxide has been increasing since the start of the Industrial Revolution, increasing from about 280 parts per million to over 410 today, and it continues to increase. The carbon that plants need to grow comes from this carbon dioxide. They bring it into the plant, they break it apart into the carbon itself, and they use that to grow.

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Rising carbon dioxide concentrations, then, should be good news for food security around the world, for making sure that people get enough to eat every day. About 820 million people in the world don't get enough to eat every day, and there's a fair amount written about how higher CO2 is going to help with our food security problem. We need to accelerate our progress in agricultural productivity to feed the 9 to 10 billion people who will be alive in 2050, and to achieve the Sustainable Development Goals, particularly Goal 2 on reducing food insecurity and increasing nutrition. 

We know that climate change is affecting agricultural productivity. The earth has warmed about 1°C since preindustrial times, changing local temperature and precipitation patterns, and having consequences on agricultural productivity in many parts of the world. It's not just local changes in temperature and precipitation, but extremes such as heat waves, floods and droughts which are significantly affecting productivity. 

That carbon dioxide, besides making plants grow, has other consequences as well -- plants, when they have higher carbon dioxide, increase the synthesis of carbohydrates, sugars and starches, and they decrease the concentrations of protein and critical nutrients. This is very important for how we think about food security going forward. 

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Almost all micronutrients are affected by higher CO2 concentrations. Two in particular are iron and zinc. When you don't have enough iron, you can develop iron deficiency anemia, which is associated with fatigue, shortness of breath and some other fairly serious consequences as well.

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When you don't have enough zinc, you can have a loss of appetite. It is a significant problem around the world and there are about 1 billion people who are zinc deficient. It's very important for maternal and child health, as it affects development. The B vitamins are critical for a whole range of reasons - they help convert our food into energy and are important for the functions of many of the physiologic activities in our bodies. However, when you have higher carbon in a plant, you have less nitrogen, and you have less B vitamins. 

And it's not just us. Cattle are already being affected because the quality of their forage is declining. In fact, this affects every consumer of plants.

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How do we know that this is a problem? We know from field studies and experimental studies in laboratories. In the field studies, focused primarily on wheat and rice, there are, for example, fields of rice that are divided into different plots, and the plots are all the same: the soil is the same, the precipitation is the same. Everything's the same, except carbon dioxide is blown over some of the plots, so you can compare what it looks like under today's conditions and under carbon dioxide conditions later in the century. 

We looked at 18 rice lines in China and in Japan, and grew them under conditions that you would expect later in the century. When you look at the results, the white bar is today's conditions and the red bar is conditions later in the century. Protein declines about 10%, iron about 8% and zinc about 5%. These don't sound like big changes, but when you start thinking about the poor in every country, who primarily eat starch, this will put people who are on the edge over the edge, into frank deficiencies, creating all kinds of health problems. The situation is even more significant for the B vitamins. 

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In another example, this is modeling work that was done by Chris Weyant and his colleagues, taking a look at this chain from higher CO2 to lower iron and zinc to various health outcomes. They looked at malaria, diarrheal disease, pneumonia and iron deficiency anemia, considering what the consequences could be in 2050. The darker the color in this, the larger the consequences. You can see the major impacts in Asia and in Africa, but also note that in countries such as the United States and countries in Europe, the populations also could be affected. They estimated about 125 million people could be affected.

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These experiments and modeling studies did not take climate change itself into account. They just focused on the carbon dioxide component, so when you put the two together, it's expected the impact is much larger than what I've told you. 

I'd love to be able to tell you how much the food you eat has shifted from what your grandparents ate in terms of its nutritional quality, but I can't. We don't have the research on that. 

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I'd love to tell you how much current food insecurity is affected by these changes, but I can't. We don't have the research on that, either. There's a lot that needs to be known in this area, including what the possible solutions could be. We don't know exactly what those solutions are, but we've got a range of options. We've got advancements in technologies, we've got plant breeding, we've got biofortification and soils could make a difference. Of course, it will be very helpful to know how these changes could affect our future health, the health of our children and the health of our grandchildren. These investments take time and it will take time to sort all these issues out. However, there is no national entity or business group that is funding this research. We need these investments critically so that we do know where we're going. 

In the meantime, what we can do is ensure that all people have access to a complete diet, not just those in the wealthy parts of the world, but everywhere in the world. We also individually and collectively need to reduce our greenhouse gas emissions to reduce the challenges that will come later in the century. 

It's been said that if you think education is expensive, try ignorance. Let's not. Let's invest in ourselves, in our children and in our planet. 

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Kristie Ebi has been conducting research and developing practice on the health risks of climate variability and change for more than 20 years, understanding sources of vulnerability, estimating current and future health risks of climate change, and designing adaptation policies for countries in Central America, Europe, Africa, Asia and the Pacific. Ebi is the author of multiple national and international climate change assessments, including the IPCC Special Report on Global Warming of 1.5C.

This is an extract from a 2019 talk delivered by Kristie Ebi entitled "How climate change could make our food less nutritious” delivered at TED2019, published under a Creative Commons Attribution License