Climate change is making plants less nutritious - that could already be hurting animals that are grazers
Published: December 21, 2024 12.17am AEDT
Ellen Welti
Research Ecologist, Great Plains Science Program, Smithsonian Institution
More than one-third of all animals on Earth, from beetles to cows to elephants, depend on plant-based diets. Plants are a low-calorie food source, so it can be challenging for animals to consume enough energy to meet their needs. Now climate change is reducing the nutritional value of some foods that plant eaters rely on.
Human activities are increasing atmospheric carbon dioxide levels and raising global temperatures. As a result, many plants are growing faster across ecosystems worldwide.
Some studies suggest that this "greening of the Earth" could partially offset rising greenhouse gas emissions by storing more carbon in plants. However, there's a trade-off: These fast-tracked plants can contain fewer nutrients per bite.
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We believe long-term changes in the nutritional value of plants may be an underappreciated cause of shrinking animal populations. These changes in plants aren't visually evident, like rising seas. Nor are they sudden and imminent, like hurricanes or heat waves. But they can have important impacts over time.
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In my opinion this has to be one of the most absurd of all the climate claims.
There is zero paleo evidence that past periods which experienced high CO2 levels suffered any negative effect due to nutrient dilution.
Most of the age of the dinosaurs occurred when CO2 levels were much higher than today. During the Cretaceous period, which ended 66 million years ago when that giant asteroid killed all the dinosaurs, CO2 levels were mostly above 1000ppm - over double today's CO2 level. Did all those T-Rex dinosaurs and all the other monstrous creatures which shook the Earth when they moved look nutrient starved?
Consider the PETM. CO2 levels during the PETM may have been as high as 2520ppm - 6x higher than today. There is no evidence life suffered during the PETM, quite the opposite. The Palaeocene-Eocene Thermal Maximum, 5-8C hotter than today, was the age of monkeys. Our mostly fruit eating monkey ancestors thrived on the abundance of the hothouse PETM, and colonised much of the world, only retreating when the cold returned.
Fish also did well during the PETM - there was a massive boom in fish life. Since the bottom of the fish food chain is plant life, this boom in fish stocks does not support the assertion higher CO2 levels lead to a drop in quality or quantity of food.
In my opinion it is become increasingly difficult for scientists to maintain claims that higher CO2 levels are bad for the ecosystem.
I'm sure it is possible to create lab experiments which show pretty much whatever you want in this domain, but the paleo evidence is that past periods of high CO2 were also periods of abundant life.