Study reveals grasshopper declines associated with declines in quality of prairie grasses

The article talks about animals which eat plants, but of course, meat eaters eat animals who eat plants, so meat eaters are also affected.

https://m.phys.org/news/2020-03-reveals-grasshopper-declines-quality-prairie.html?fbclid=IwAR2DbKMNgPxGfnNmLaIaFbazAfvbIpUa5vQOUrvoYnKKfBQMbQUkoSP-pxA

March 11, 2020 , University of Oklahoma

A University of Oklahoma-led study shows that grasshopper numbers have declined over 30% in a Kansas grassland preserve over the past two decades. Published in the Proceedings of the National Academy of Sciences, the paper, "Nutrient dilution and climate cycles underlie declines in a dominant herbivore," reveals a new potent and potentially widespread threat to Earth's plant feeders: the dilution of nutrients like nitrogen, phosphorus, and sodium in the plants themselves due to increasing levels of atmospheric CO2.

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Grasshoppers are abundant consumers in grasslands—a habitat that covers more than 30% of Earth's land mass and is the source of the majority of human crops. The same decline in plant quality revealed by Welti and her colleagues has recently raised alarms about the global human food supply.

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Welti and her colleagues' second discovery—that plant quality is declining even as plant growth has nearly doubled—highlights the paradoxical nature of nutrient dilution.

"The greenhouse gas CO2 is heating the Earth and acidifying its oceans, but it is also the main ingredient in the sugars, starches, and cellulose of plants," Kaspari said. "When we pump the atmosphere full of CO2, we build more plants. But, with no additional nutrients to fertilize them, the nutritional value of each bite is diluted. Mouthful by mouthful, the prairie provides less and less food to the grasshoppers. Hence, their decline."

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"Of late, much has been made of 'greening the Earth' as a tool to fight climate change," Kaspari said. "We show that while growing plants may indeed help scrub CO2 from the atmosphere, those same plants are likely becoming and less nutritious. It is as if, by burning fossil fuels, humans are transforming all of our kale into iceberg lettuce: still edible, but less and less sustaining."