Is Climate Change Making Our Food Less Nutritious?

Recent studies suggest that climate change could be reducing the nutrient content of certain crops. But is it true? Read on to discover how carbon emissions might undermine even the healthiest of diets.

Climate change is causing dramatic alterations in the global environment. We’re seeing more frequent and intense droughts, storms, floods, and heat waves.¹ Inevitably, these changes are affecting the way we produce food. And the results are unpredictable.

In some circumstances, climate change can contribute to longer growing periods and, therefore, result in greater yields. But extreme weather events like severe droughts can mean crops die before harvest. Atmospheric levels of carbon dioxide are linked to a changing climate, which impacts our yields. But more carbon dioxide has another, more direct impact on crops: it can make our food less nutritious.

What’s making our food less nutritious?

We’ve known that our food has been getting less nutritious for some time. One of the first large studies to draw attention to this topic was published in 2004 and found that six nutrients in several garden crops had dropped by up to 38% between 1950 and 1999.² According to several studies, multiple factors are contributing to the changes in the nutrient content of our crops. One of the major factors is human-caused carbon dioxide emissions.³

Since the Industrial Revolution, our global carbon dioxide levels have increased from about 280 parts per million (ppm) to about 420 ppm today, and rising.⁵ These emissions are causing rapid climate destabilisation that affects how we produce food.

According to Matthew Smith, a research scientist in environmental health at Harvard’s T.H. Chan School of Public Health:

“Just having higher carbon dioxide levels in the atmosphere, regardless of its impact on weather or climate, changes the way the plants grow and their nutritional content."

And it’s not just our crops that are having their nutrient density affected by changes in carbon dioxide. The declining quality of livestock forage is also having a knock-on effect on the meat and dairy we’re consuming.⁴

The confusing part is that carbon dioxide also stimulates plant growth. Through the process of photosynthesis, plants absorb carbon dioxide, break it apart to get to the carbon and use this to grow.⁶ This has given rise to the argument that added carbon dioxide is good for plants, and in part, that’s true. But it’s more complex than that.

Carbon dioxide and crop yields

Technically, with rising carbon dioxide levels, we should be able to produce more food. And in the last 50 years, as carbon dioxide levels have skyrocketed, yields have also shot up. For example, between 1961 and 2014, the average global cereal yield rose by 175%.⁷

Of course, much of this growth has been attributed to greater use of higher-yielding crop varieties, expanding the area of farmed land and using chemical inputs such as fertilisers and pesticides - not only greater quantities of atmospheric carbon dioxide.

Still, as a standalone factor, carbon dioxide does speed up crop growth. However, the overall impact of climate change, also catalysed by increased greenhouse gases like CO2, will mean a reduction in world harvests. While this threatens food security more significantly than the reduced nutrient content of food, which is also correlated with rising carbon dioxide concentrations, both of these issues need to be taken seriously.⁸

How does carbon dioxide make our food less nutritious?

The rise in atmospheric carbon dioxide has created an imbalance between air and soil. There’s more carbon dioxide in the air, but the soil hasn’t seen a similar increase in nitrogen, phosphorus, potassium, calcium or any of the other nutrients that plants need to grow and metabolise.⁹

This imbalance translates into the chemistry of plants, which are becoming carbon-rich but micronutrient-poor. “In essence, the chemistry we rely on for our nutrition, protein, vitamins and minerals is out of whack,” Lewis Ziska, Associate Professor of Environment Health Sciences at the Columbia Mailman School of Public Health, told FoodUnfolded.

Plant physiology studies have already seen this effect in major staples, such as wheat and rice. Their research indicates that the staples respond to higher atmospheric CO₂ levels by increasing the synthesis of carbohydrates (e.g. starches and sugars) and reducing the quantity of nutrients.¹⁰

Other factors making our food less nutritious

As well as carbon dioxide emissions, soil degradation and biodiversity loss can also affect the nutritional content of our food.

Soil Degradation

Industrial agricultural processes, such as how we choose to irrigate, manage weeds, fertilise and harvest, can disturb soil health. Generally speaking, heavy machinery, overgrazing, and the overuse of synthetic inputs can damage soil structure and impede interactions between plants and soil microorganisms. This is important because a healthy soil structure, teeming with microbes, is how the plant can get all the water and nutrients needed to thrive.¹¹

Soil salinisation, acidification and pollution also make our food less nutritious. Acidification, for example, accelerates the leaching of nutrients from the soil, resulting in nutrient deficiencies in plants.¹² These factors can interact with climate change. For example, there is evidence that as soil temperatures increase, the concentration of arsenic in rice also increases.¹³

Learn more about why soil matters

Biodiversity Loss

Biodiversity losses could also reduce the diversity of nutrients available for human consumption. The extinction or loss of crop species and pollinators would reduce the variety of food types and could destroy the availability of key wild-harvested foods.^14,15

Additionally, biodiversity loss can have a more general effect on the health of our crops and animals. This is because a biodiverse landscape helps us control pests and diseases, maintain a healthy water cycle, and ensure pollination.

How will declining nutrition impact our food future?

The World Health Organisation estimated in 2021 that as many as 828 million people are food insecure, meaning they do not have reliable access to sufficient quantities of safe, nutritious and affordable food.¹⁵ But even more people - over 2 billion - already have deficiencies in micronutrients such as iron and zinc.¹⁶

Greater concentrations of atmospheric CO₂ are causing relatively small percentage changes in the density of nutrients in the crop - a 10% reduction in protein, an 8% reduction in iron, or a 5% reduction in zinc. These might not sound like differences that will vastly alter our nutritional balance, but for people already on the edge of food insecurity or nutrient deficiencies, these small changes could push them over the edge.¹⁶

A recent study found that by 2050, about 175 million people are expected to become newly zinc deficient and 122 million people to become newly protein deficient.³ This is worrying because zinc is important for skin health, immune system function, cell growth, and fighting bacteria and viruses. Protein, meanwhile, helps us build and repair muscles and makes hormones and enzymes essential for life.

According to Smith, “You don’t start to see very strong effects until people start becoming moderately or severely deficient, but it then has a much bigger effect on their health. The problem is that you don’t hunger for iron or zinc; you hunger for calories. So if you're eating roughly the same amount of calories, but you're losing the nutrition, you won't necessarily compensate. It’s a sneaky effect, and it’s a huge burden on human health,” Smith said.

Disproportionate impacts

Declining nutrition of staple crops will disproportionately impact populations and communities already experiencing nutritional deficiencies. These populations tend to be lower income and more reliant on vegetarian diets or staple crops.³

For example, a study into the effect of the decreasing nutrient density of rice found that expectant mothers in rice-dependent countries would be disproportionately impacted.^19,20 This is because people in countries which rely on rice, such as Bangladesh and Cambodia, will get less protein, iron, zinc and four major B vitamins, which are key to foetal and early child development.^19,20

A common public health approach to nutrient deficiencies suggests giving everybody supplements. But supplements do not offer the same nutrient makeup as whole foods, which contain not only vital nutrients but also antioxidants, fibre and substances that help with healing and inflammation.²¹

According to Kristie Ebi, a Professor of Global Health at the University of Washington in Seattle, there will be locations where supplementation is going to be needed, but first, there are some better solutions to ensure that our crops are nutrient-dense.

What’s the solution to the declining nutrition of food?

The increasing concentration of atmospheric carbon dioxide is fundamentally altering the composition of plants, but it’s not the only thing affecting the nutritional content of our food.

“We need a range of solutions that tackle all areas of the problem, with a sense of what the interactions between climate change, carbon dioxide and soil changes mean for the nutrients in our food,” says Ebi.

1. Emissions Reductions

We need to tackle the cause of rising carbon dioxide concentration in the atmosphere: emissions from fossil fuels. Significantly reducing greenhouse gas emissions by 2050 will mean we don’t have to worry as much about the changes in nutrient density.

2. Plant Breeding 

We also need to prepare for a scenario where we don’t manage to reduce emissions by investing in plant breeding and biofortification. This involves research and work on developing crops better suited to retaining nutrients even under increased atmospheric carbon dioxide. This could be done through conventional breeding or biotechnology-based approaches such as genetic engineering or genome editing.²²

3. Soil Conservation

We need to stop and reverse the degradation of our soils. Nurturing our soils through regenerative agricultural practices will create an environment conducive to healthy plants. A focus on regenerative agriculture will also provide opportunities to sequester carbon in the soil. This will remove carbon dioxide from the atmosphere and ensure soils are more resilient to the effects of a changing climate.

4. Financial Incentives

We can also encourage behaviour change at the farm level. Currently, farmers are incentivised by crop yields, not crop nutrient content. Creating financial incentives that reward high nutrient density would provide a reason for farmers and food producers to increase the nutritional value of their food.

5. Further Research

We need much more research in this area. Studies cited in this article that measured the changes in nutrient content in crops grown under artificial carbon dioxide concentrations only considered the effect of greenhouse gases on the food. Taken together with the effects of climate change and soil degradation, the nutrient decrease could be even larger than first thought.