What do I study?

Species are facing an unprecedented combination of stressors which have implications for both population trends and species distributions. I study the impacts of these various stressors on insects generally and on butterflies in particular. Butterflies are perhaps the most well studied insects worldwide, which makes them great organisms for understanding long term change. A major aspect of my work continues the longest observational study of insects in North America. The study spans an elevational gradient from the Central Valley to the Sierra Nevada mountains in California. Sites along this transect have been monitored every other week for over 40 years by Dr. Arthur Shapiro at UC Davis. More information about these data can be found here and here.

Some of my questions:

How is climate change impacting butterfly populations dynamics and distributions?

Species are expected to shift poleward and to higher elevations to compensate for higher temperatures. While temperatures may be similar, butterflies will encounter different plants and enemies in different regions, both of which are critical for survival. I am interested in how realistic the expectation of distributional shifts is in nature.

How is the impact of climate on butterflies mediated by host plant interactions?

Caterpillars are among the most important defoliators on Earth. Often their relationships with host plants are very specific and a species of butterfly can only eat a particular type of plant. I am interested in how climate change directly impacts butterfly development, but also how it impacts the quality and timing of the plants the butterfly is consuming.

How do different Anthropogenic threats work independently and in concert to drive butterfly population trajectories?

Populations are facing a multifaceted suite of stressors which includes habitat loss, agricultural intensification, urbanization, and climate change (to name a few). Of these, climate change is ubiquitous and is impacting all populations on Earth, including those facing other threats. As the intensity of climate change continuous to grow, predicting how already imperiled populations will respond is of fundamental importance for conservation.


Forister, M.L., Halsch, C.A., Nice, C.C., Fordyce, J.A., Dilts, T.E., Oliver, J.C., Prudic, K.L., Shapiro, A.M., Wilson, J.K., and Glassberg, J. (2021) Community scientists see fewer butterflies across the warming and drying landscapes of the American West. Science 371: 1042-1045 PDF

Halsch, C.A., Shapiro, A.M., Fordyce, J.A., Nice, C.C., Thorne, J.H., Waetjen, D.P., and Forister, M.L. (2021) Insects and recent climate change. Proceedings of the National Academy of Sciences 118: e2002543117 PDF

Halsch, C.A., Code, A., Hoyle, S.M., Fordyce, J.A., Baert, N., and Forister, M.L. (2020)  Pesticide contamination of milkweeds across the agricultural, urban and open spaces of low elevation Northern California. Frontiers in Ecology and Evolution 8 PDF

Halsch, C.A., Shapiro, A.M., Thorne, J.H., Waetjen, D.P., and Forister, M.L. (2020) A winner in the Anthropocene: changing host plant distribution explains geographic range expansion in the gulf fritillary butterfly. Ecological Entomology 45:652-662 PDF

Kimball, S., Long, J.J., Ludovise, S., Ta, P., Schmidt, K.T., Halsch, C.A., et al. (2019). Impacts of competition and herbivory on native plants in a community‐engaged, adaptively managed restoration experiment. Conservation Science and Practice 1:e122 PDF

Tamura, N., Lulow, M.E., Halsch, C.A., Major, M.R., Balazs, K.R., Austin, P., et al. (2017). Effectiveness of seed sowing techniques for sloped restoration sites. Restoration Ecology 25:942-952 PDF