What do I study?
Species are facing an unprecedented and multifaceted set of stressors which is impacting population dynamics and species distributions. I study how these stressors affect butterflies. As a group, 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.
Some of my questions:
What aspects of climate change are having the greatest impact on butterfly populations?
The pathways through which climate can affect butterflies are myriad. Temperatures are rising, especially at night, and precipitation patterns are changing. In the west this has meant warmer and drier conditions especially in the Fall. Additionally while means are changing, extreme events are becoming more common. Understanding which of these influences which butterflies is critical for predicting butterfly responses to further change, especially in natural areas.
How do different Anthropogenic threats work independently and in concert to drive butterfly population trajectories?
Populations are facing many stressors like habitat loss, agricultural intensification (including pesticide use), urbanization, and climate change. Of these, climate change is ubiquitous and is impacting all species 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.
How are the impacts of Anthropogenic stressor mediated by host plant interactions?
While adults butterflies are the most apparent life stage, the caterpillar stage is where many Anthropogenic threats will be realized. As non-native plants have proliferated across the west many butterflies have switched to using non-native host plants. I am interested in how a caterpillar can handle different threats when using a native versus a non-native host plant.
Forister, M. L., Grames, E. M., Halsch, C. A., Burls, K. J., Carroll, C. F., Bell, K. L., Jahner, J. P., Bradford, T., Zhang, J., Cong, Q., Grishin, N. V., Glassberg, J., Shapiro, A. M., and Riecke, T. V. (in review) Assessing risk for butterflies in the context of climate change, demographic uncertainty, and heterogenous data sources.
Halsch, C. A., Hoyle, S. M., Code, A., Fordyce, J. A., Forister, M. L. (2022) Milkweed plants bought at nurseries may expose monarch caterpillars to harmful pesticide residues. Biological Conservation 273: 109699 PDF
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) Fewer butterflies seen by community scientists 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