Geographic variation in migratory grasshopper recruitment under projected climate change

Authors: Humphreys Jr, John; Srygley, Robert; Branson, David - Dave

Submitted to: Geographies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2022
Publication Date: 1/27/2022
Citation: Humphreys Jr., J.M., Srygley, R.B., Branson, D.H. 2022. Geographic variation in migratory grasshopper recruitment under projected climate change. Geographies. 2(1):12-30. https://doi.org/10.3390/geographies2010003.
DOI: https://doi.org/10.3390/geographies2010003

Interpretive Summary: Climate change is expected to alter prevailing climate conditions this century and possibly altering insect populations and increasing the frequency and intensity of rangeland and crop impacts by grasshoppers. We leveraged ten-years of migratory grasshopper field surveys to assess the response of nymph recruitment to projected climate conditions through the year 2040. The migratory grasshopper (Melanoplus sanguinipesis) is one of the foremost pests of grain, oilseed, pulse, and rangeland forage crops in the Western United States. To assess nymph recruitment, we developed a new statistical model that individually assessed nymph and adult life stages while considering total population size and data collection biases. Our results indicated that nymph recruitment rates will exhibit strong geographic variation under projected climate change, with population sizes at many locations being comparable to those historically observed, but other locations experiencing increased insect abundances. Our findings suggest that alterations to prevailing temperature and precipitation regimes as instigated by climate change will amplify recruitment, thereby enlarging population sizes and potentially intensifying agricultural pest impacts by 2040.

Technical Abstract: Climate change is expected to alter prevailing climate conditions this century, thereby modifying insect demographic processes and possibly increasing the frequency and intensity of rangeland and crop impacts by pest insects. We leveraged ten-years of Melanoplus sanguinipes field surveys to assess the response of nymph recruitment to projected climate conditions through the year 2040. Melanoplus sanguinipesis is one of the foremost pests of grain, oilseed, pulse, and rangeland forage crops in the Western United States. To assess nymph recruitment, we developed a multi-level, joint modeling framework that individually assessed nymph and adult life stages while concurrently incorporating density-dependence and accounting for observation bias connected to preferential sampling. Our results indicated that nymph recruitment rates will exhibit strong geographic variation under projected climate change, with population sizes at many locations being comparable to those historically observed, but other locations experiencing increased insect abundances. Our findings suggest that alterations to prevailing temperature and precipitation regimes as instigated by climate change will amplify recruitment, thereby enlarging population sizes and potentially intensifying agricultural pest impacts by 2040.