OU Biologist Reveals Wicked Problem in Global Plant Nutrition

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NORMAN, OKLA. – Michael Kaspari, a professor of biology in the University of Oklahoma School of Biological Sciences, has published research in the journal Trends in Ecology and Evolution that highlights nutrient dilution in plants and its cascading impact on the animals and insects that eat this less nutritious food.

“Every living thing on the planet is made out of chemical elements, including plants,” Kaspari said. “However, we now have ample, disturbing evidence that the concentration of these essential elements has been declining for the last 20-30 years. That means that every bite an herbivore takes has less and less nutrition.”

Kaspari explains that the quality of our food supply is decreasing at a time when the quantity is increasing. The research, which is funded by the National Science Foundation, shows that nutrient dilution is a widespread, global phenomenon.

“This situation is tied closely to the increase in carbon dioxide in the atmosphere,” he said. “The carbon dioxide is acting as its own fertilizer, but it’s adding empty carbohydrates to the world’s food supply. This results in ‘green deserts’ which are fields and forests full of plants with empty carbs.”

As the amount of carbon dioxide in the atmosphere increases, plants grow larger. However, since there are no additional nutrients in the soil, the quality of the vegetation decreases.

“It’s the equivalent of taking a field of kale and converting it to iceberg lettuce,” he said. “And while we have perhaps 30% more plant matter on the planet today than we did 100 years ago, much of it is empty calories. This decline is leading to a loss of plant-eaters and is impacting the predators that eat the plant-eaters.”

Research shows that the global insect population is declining at approximately 1.5% annually, even though prairie vegetation is double what it was 20 years ago. This has led to a 37% decline in grasshopper populations in the Konza Prairie during that same period.

“Insect declines are a wicked problem that has a lot of moving parts,” he said. “To address this problem, some suggest eliminating pesticides or restoring habitats. Those things will help, but to make real strides, we must reduce the amount of carbon dioxide in the atmosphere. That will require a lot of ingenuity and cooperation.”

According to Kaspari, this situation is also impacting the human food supply and is likely already leading to poor health outcomes for impoverished communities around the globe. 

“These communities, already dealing with famine and malnourishment, must now also contend with developmental abnormalities and higher fetal mortality due to the lack of essential micronutrients like zinc and iron that help them grow,” he said. “If we care about our fellow human beings, then we must take this seriously and act now.” 

Learn more about the Kaspari Lab at the University of Oklahoma and read the full study, "Nutrient Dilution and the Future of Herbivore Populations," published in Trends in Ecology and Evolution, DOI no. 10.1016/j.tree.2024.05.001.