Climate Change and Nutrition by Christina Badaracco, MPH
Updated: Apr 7
At a time when our country is developing and debating the latest version of the farm bill, agricultural sustainability is at the forefront of people’s minds. Support for conservation programs and local food systems has increased under recent bills, and we hope that this trend will continue. Meanwhile, the atmospheric concentration of carbon dioxide exceeded 411 parts per million in June 2018—the highest level ever recorded. Climate change and nutrition are closely linked; indeed, an emerging field of research is indicating that increasing temperatures and climatic uncertainty may reduce the quality of the food we grow in the US and across the globe, thereby affecting diets and long-term public health. How does food production contribute to climate change? The potential contribution of our food system to climate change is widely known. The methods we use to produce and transport food in industrialized agricultural systems require enormous amounts of energy, and the burning of fossil fuels yields greenhouse gasses, which contribute to global warming. Carbon dioxide, CO2, also causes ocean acidification and nitrogenous compounds leading to algal blooms that create dead zones devoid of aquatic life in bodies of water downstream from the farms that release them. You can read more about these effects in this previous post. Due to increases in efficiency of machinery, increased chemical production and higher demand for storage, long-distance transportation and added processing, Americans now expend twice as much energy processing and transporting foods as we do to produce them. And because we waste 40% of the food we produce, decomposition of food on farms and in homes also releases methane, another greenhouse gas. The illustration below shows the estimated anthropogenic contributors to global emissions, with food-related emissions accounting for roughly half of the greenhouse gas emissions.
How does climate change affect food production? We have known for years about the potential threats to agriculture from a changing climate, ranging from the increased variability that interferes with forecasting to changing patterns of rain that drive flooding or drought, respectively. This unpredictability could reduce crop yields by creating less favorable conditions in many parts of the world. Less well known is the impact of climate change on the nutritional quality of the foods we eat. Recent studies suggest that changing climatic conditions may be reducing the nutritional quality of crops we grow and consume every day. Plants typically experience some degree of nutrient limitation that keeps their growth in check. The carbon dioxide in the environment and the carbon that plants use to make molecules and form energy through photosynthesis are typically kept in balance. But just as depletion of soil nutrients due to intensive agriculture has reduced their content in plants, this carbon balance may also be thrown off when ambient carbon dioxide increases. The results of a 2018 international study of rice, which is a staple crop for populations ranging from Central America to East Asia, showed this disturbing trend. When exposed to higher carbon dioxide (reflecting amounts predicted by the end of the century), 18 varieties of rice contained fewer B vitamins, protein, iron, and zinc. These nutrients are critical for everyone, but they are even more essential among populations that rely primarily on plant-based diets, such as those in developing countries. A meta-analysis of the nutritional impact of elevated CO2 levels (i.e., above about 550 ppm predicted for the mid-21st century), which was published in Nature magazine in 2014, had already shown that grains and legumes grown under elevated CO2 contained less zinc and iron. The authors explained that these nutrients are already deficient in more than two billion people worldwide; they will be even less available and potentially drive more deficiency diseases (such as iron-deficiency anemia, impaired wound healing, and/or reduced fertility) by the middle of the century. This study also showed that the protein content in wheat and rice would decrease by 6.3 and 7.8 percent, respectively. This is of particular concern, once again, for developing countries where people more commonly rely on plant-based sources of protein for a balanced diet. USDA researchers are studying these trends at the Adaptive Cropping Systems Laboratory near Washington, DC. Comparing growth under pre-industrial carbon dioxide levels to almost 600 ppm (modified in free-air CO2 enrichment), they have found that coffee plants, as an example, grow to be larger—likely due to accelerated photosynthesis. They hypothesized that this growth dilutes the nutritional value of beans (such as the protective antioxidants) and this mechanism may apply to other crops, as well. Because of differences in impacts across species, researchers are suggesting that breeders need to select for crops with decreased sensitivity to atmospheric CO2 concentration.
Another 2016 study conducted by USDA scientists demonstrated how climate change would affect bee colonies by reducing the nutritional quality of the goldenrod they eat. Beyond this study, the potential effects of climate change on animal agriculture have received little attention. Cows surely rely on nutritious grasses; as do hens, who also eat the insects that live in healthy soil. If these animals' dietary quality decreases, so would the animal products—rich sources of protein, fat, iron, calcium and other micronutrients—that humans eat. And with less supply for feed to begin with, the carrying capacity of animals may also fall.
What can you do to reduce your “carbon foodprint”? While consumers don’t play much of a role in the research on nutritional impacts of climate change or on more resistant strains of crops, we can seek to make food choices that minimize our collective impact on climate change.
Here are some suggestions.
Grow any amount of food at home. Not only do you save money and use less energy, but you can reduce waste by harvesting just as much as you can use immediately.
Buy locally. You can drastically reduce the fossil fuels required to transport foods across long distances, or even across the world, by eating foods grown in-season and close to home. Savor stone fruit in the summer so you can look forward to apples in autumn!
Reduce food waste at home. Buy smaller loads of groceries, use your eyes and nose to tell if something has expired (and not necessarily the marked date), and share your surplus with neighbors. Many foods, such as prepared soups and cooked vegetables, can be stored in glass in the freezer for a future meal. Canning and fermenting are other options to preserve summer’s bounteous produce. Inedible scraps can be easily made into vegetable stock or added to meat bones for a meat stock. Many plants have more than one edible component, as well; the tops of carrots and beets, for example, can be cooked down or made into pesto.
Buy seconds from your farmers' market. They might have small defects that prevent them from being sold for full price, but they are just as nutritious and delicious and would otherwise go to waste.
Buy meat raised on pasture. While beef and other animals have a reputation for being energy-intensive, animals raised on pasture require much less energy because their food supply can be grown right on the farm and they don’t require nearly as many chemical inputs to grow and stay safe to eat.
Limit purchasing foods in packages. Buying food in bulk, rather than individual containers, reduces the energy required for processing and manufacturing of the virgin materials. When you do need to buy food in a package, look for a recycling symbol on plastics so you can recycle as much as possible.
Our methods of producing food and the choices we make at the grocery store or restaurant can contribute negatively to climate change. It's also becoming increasingly evident that climate change can impair the nutritional quality of the food we produce. Following diets full of seasonal, local and least-processed foods is the best way we have of ensuring our health today and protecting our environment for future generations.
Earth System Research Laboratory Global Monitoring Division. “Trends in Atmospheric Carbon Dioxide.” US Department of Commerce. Updated June 5, 2018. www.esrl.noaa.gov/gmd/ccgg/trends/
Gunders D. “Wasted: How America Is Losing Up to 40 Percent of Its Food from Farm to Fork to Landfill.” National Resources Defense Council Issue Paper (2012).
Kennedy M. "As Carbon Dioxide Levels Rise, Major Crops Are Losing Nutrients". June 19, 2018. NPR’s The Salt. www.npr.org/sections/thesalt/2018/06/19/616098095/as-carbon-dioxide-levels-rise-major-crops-are-losing-nutrients
Meyers S, et al. "Increasing CO2 threatens human nutrition." Nature 2014; 510: 139—143.
Zhu C et al. “Carbon dioxide (CO2) levels this century will alter the protein, micronutrients, and vitamin content of rice grains with potential health consequences for the poorest rice-dependent countries.” Science Advances 2018; 4(5): eaaq1012.
Ziska LH, et al. "Rising atmospheric CO2 is reducing the protein concentration of a floral pollen source essential for North American bees." Proceedings of the Royal Society B 2016; 283:20160414.
Christina Badaracco, MPH
Christina is a dietetic intern at Massachusetts General Hospital. She recently earned her Master of Public Health degree from the University of California, Berkeley. She is pursuing a career in nutrition to improve access to healthy and sustainable food and educate Americans about the connections between food and health. She loves to experiment with healthy recipes in the kitchen and share her creations to inspire others to cook. She graduated with a degree in Ecology and Evolutionary Biology from Princeton University, after conducting her thesis on sustainable agriculture and energy in Kenya. She has done clinical nutrition research at the National Institutes of Health, menu planning and nutrition education at the Oakland Unified School District and communications at the Environmental Protection Agency’s Office of Water. She has also enjoyed contributing to children’s gardens, farmers’ markets and a number of organic farms. email@example.com www.linkedin.com/in/christina-badaracco/
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