Nutrient dilution and insect decline

A study finds that the dilution of nutrients in plants, alongside climate factors, drives insect herbivore decline. Insect populations are declining worldwide. One hypothesis for the drivers behind such declines holds that increasing plant productivity, due to favorable climate oscillations or carbon dioxide fertilization, can dilute the amounts of essential nutrients in plant biomass. Such nutrient dilution can in turn stress populations of insect herbivores. Ellen A. R. Welti and colleagues tested the hypothesis using data series from a prairie in Kansas covering 16 and 22 years. The data included plant biomass, plant elemental composition, grasshopper abundances, and climate data. Grasshopper abundances exhibited 5-year population cycles as well as declines between 2.1 and 2.7% per year. Natural climate cycles, such as the El Niño Southern Oscillation, North Atlantic Oscillation, and Pacific Decadal Oscillation, accounted for 40-54% of the grasshopper population variation, through effects on local climate and plant productivity. However, grass biomass doubled over the study period, with a corresponding decrease in the amounts of nitrogen, phosphorus, potassium, and sodium in leaves. The dilution accounted for 25% of the grasshopper decline. According to the authors, climate change may cause widespread nutrient dilution, even in relatively undisturbed natural areas.

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Article #19-20012: “Nutrient dilution and climate cycles underlie declines in a dominant insect herbivore,” by Ellen A. R. Welti, Karl A. Roeder, Kirsten M. de Beurs, Anthony Joern, and Michael Kaspari.

MEDIA CONTACT: Ellen A. R. Welti, University of Oklahoma, Norman, OK; e-mail:

[email protected]