CO2: Friend or Foe to Food?

How Rising Carbon Dioxide Uproots Bangladesh’s Food Systems

Credit: Sharafat Raheb/Unsplash

Irrigated by the Bengal Delta’s meandering rivers, Bangladesh’s fertile lands supply an abundant and nutritionally balanced diet of rice and fish. Ranked fourth in the global production of milled rice and second in freshwater fish production, the country’s agricultural prowess is increasingly scourged by socio-economic and ecological shocks on its fragile and low-lying ecosystem.

Droughts, floods, and sea level rise are not the only threats to Bangladesh’s food security. Scientists worry that rising atmospheric carbon dioxide (CO2) will produce ominous knock-on effects on the quantity of nutritional supplies available. Less spotlighted, but equally concerning are its impacts on the quality of Bengalis’ diets, however.

Whereas carbon-induced ocean acidification runs the risk of removing essential fish-based nutrients, excess atmospheric CO2 could lead to carbohydrate dilution of agricultural crops – a process by which plants’ carbon dioxide-stimulated carbohydrate production dilutes the rest of the grain components. Given that Bengalis derive two-thirds of their calorie supply and over half of their protein intake from fish and rice, nutritional deficiency may be looming.

The Mauna Loa Observatory confirmed in May 2021 that atmospheric carbon concentration had reached 420 parts per million (ppm). This means that for every one million particles of air there are 420 particles of CO2 – widely past the commonly agreed safe level of 350 ppm. Climatologists warn that the current rate of emissions would lead to a doubling of pre-industrial concentration, from 280 ppm to 550 ppm, within the next half century. But how would this excess carbon impact upon our food systems?


It is estimated that a third of the additional emissions will be absorbed by oceans, reacting with seawater to form carbonic acid. The resulting ocean acidification is detrimental to phytoplanktons – the microscopic plants available in the upper sunlit layer of oceans. Since phytoplanktons are the foundation of the ocean’s food chain, ocean acidification is likely to disrupt natural competition by promoting some species to grow slower than others, pushing the laggards to extinction. But diminishing marine biodiversity is not only problematic on its own terms: The oceans also provide for 80% of the global fish catch and feed millions around the planet.

Even where diets shift to other sources of energy intake, losses in fish production risk cuttingessential fatty acids (i.e., Omega 3 and 6) that human bodies cannot sufficiently generate from alternative foods. In addition to these indispensable nutrients, Bangladesh also relies heavily on fish consumption for complements in vitamin D, iodine, iron, calcium, zinc, and other minerals. Economically accessible substitutes are by and large out of reach for many Bengalis at the moment, whereas rising ocean acidification already threatens to deprive the 15% of the global population that depend on fish-based diets of essential health benefits.


Although even climate sceptics increasingly acknowledge the impact of human-induced CO2 emissions on marine systems, they disagree as to its potential consequences on agricultural production. For instance, Lamar Smith – former Chair of the U.S. House Committee on Science, Space and Technology – claims that additional atmospheric carbon could fuel plant growth and calls for the ‘hysteria over carbon dioxide’ to be overcome. Like Björn Lomborg, the controversial author of The Skeptical Environmentalist (2001) and False Alarm (2020), Smith considers CO2 as fertiliser, boosting the photosynthesis process of plants,which in turn contributes to increased plant growth’ and ‘correlates with a greater volume of food production and better-quality food.’

While there is some evidence for the first claim – the positive ripple effects on plant growth –, the majority of global agricultural produce has lost its nutrient contents (i.e., minerals, vitamins, and protein) over the past 50 to 70 years. This decline has been driven by rising CO2 concentration, as the research of mathematician Irakli Loladze reveals. Loladze was one of the first to challenge the prevailing view of nutrient collapse as resulting from crop-breeding and yield-centric crop selection. Past studies had largely overlooked the relationship between rising CO2, plant quality, and human nutrition. Surveying 130 varieties of plants and analysing 15,000 samples collected over the past three decades, Loladze found that the overall concentration of minerals like calcium, magnesium, potassium, zinc, and iron had dropped by an average of eight percent.

‘Hidden hunger’ caused by nutritional deficiencies stunt cognitive development and increasing malnutrition.

These alarming results are consistent with a 2014 paper published in Nature that compared six crops (rice, wheat, maize, soybeans, field peas, and sorghum) grown in free-air CO2 enrichment (FACE) experimental locations in Japan, Australia and the United States at ambient (363-386 ppm) and elevated (546-586 ppm) CO2 concentrations. The study found that elevated CO2 is associated with significant decreases in the concentrations of zinc and iron in all C3 grasses and legumes, which represent 95% of global plant species. According to data from 2010, roughly 4.2 billion people received at least 60% of nutrients from these crops.

Reductions in zinc and iron content in food can cause considerable mineral deficiency and exacerbate existing diseases associated with high carbohydrate food consumption. However, such dietary deficiencies in micronutrients are often not immediately visible or easily observed. This ‘hidden hunger’ seriously affects the health of the metabolism and immune system, stunting cognitive development and increasing malnutrition – particularly in children.

Scientists’ future projections of changes to plants’ chemical balance are therefore dire. As minerals fall and carbohydrates increase, the plant metabolism deteriorates; crops become ‘junk food’. Effectively, CO2-stimulated carbohydrate production dilutes the rest of the grain components. This phenomenon – carbohydrate dilution – is plaguing food quality in both developed and developing countries. In rural India, one-third of the rural population is at risk of not meeting dietary protein demand. In the United States, the creeping substitution of protein with carbohydrates has increased the risk of hypertension, lipid disorders, and coronary heart disease. If these trends continue unabated, the second Sustainable Development Goal of ending hunger, achieving food security, improving nutrition, and promoting sustainable agriculture by 2030 becomes increasingly difficult to attain.

The negative impacts of increasing atmospheric CO2 on food quality and production raise significant public health concerns for countries like Bangladesh where rice and fish not only supply energy and protein but also undergird cultural identity. As the saying goes: Mache Vate Bangali (Fish and Rice make a Bengali).


Azmal Hossan is a PhD student of Sociology and National Research Trainee of Interdisciplinary Training, Education and Research in Food-Energy-Water Systems (InTERFEWS) at Colorado State University, USA. He is also an Agent of Change in Environmental Justice Fellow at The George Washington University, USA. He can be reached at and on Twitter.