Malnourished Insects: Higher CO2 Levels Make Plants Less Nutritious | naked capitalism

Why It Matters

Ecologists have thus far focused on pesticide use and the loss of native habitats as causes for insect declines.

These factors aren’t likely at the large native prairie reserve where I work. Yet the 2% per year decline in grasshoppers our study found is eerily similar to the 2% declines reported from long-term studies around the globe of moths and butterflies, whose young – caterpillars – are also voracious plant feeders.

Other factors, like pesticide use and habitat destruction, are certainly hurting insect populations in many places. But since CO2 is increasing globally, my colleagues and I suspect that nutrient dilution is likely bad news for plant-eating insects across a huge variety of habitats, in both pristine and degraded ecosystems. And since insects are crucial parts of all terrestrial food webs, their loss affects many other organisms from plants to birds.

How We Do Our Work

Konza Prairie is a large protected prairie in northeastern Kansas, and researchers have been collecting data on the grasses, insects, and animals there since the early 1980s. My colleagues and I relied on this long-term data and physical samples from years past to perform our study.

Grasshopper numbers fluctuate on a roughly five-year cycle that follows changes in the climate, like the El Niño Southern Oscillation. Having a decades-long data set allowed my colleagues and me to clearly separate these cycles from the long-term population decline and see how increasing CO2 levels played a part.

This kind of data is surprisingly rare, which has led to a good deal of controversy regarding the ubiquity of insect declines. Sites like the Konza Prairie (part of the NSF-funded Long-Term Ecological Research Network) are on the front lines in documenting Earth’s changing ecosystems.
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