Research
Extreme weather over short time scales
Extreme weather events that take place over months, weeks or even days, such as heat waves, cold snaps, and drought and increasing in frequency and intensity. We use a combination of distribution modeling, movement analysis, and bioacoustics to explore how diverse North American bird species are responding to extreme weather across seasons. By examining how responses vary across functional trait guilds, we can anticipate which species are most likely to be at risk. In an ongoing collaboration with a colleague at Berkeley and the USGS and USFWS, we are exploring how individual animals move in response to extreme weather events. Other ongoing will is exploring how populations vary in their responses to extreme weather within species.
Cohen, J., Fink, D., Zuckerberg, B. 2020. Avian responses to extreme weather across functional traits and temporal scales. Global Change Biology, 26(8), 4240-4250. PDF
Cohen, J., Fink, D., Zuckerberg, B. 2021. Extreme winter weather disrupts bird occurrence and abundance patterns at geographic scales. Ecography, 44, 1143-1155. PDF
Cohen, J. , Fink, D., Zuckerberg, B. 2023. Spatial and seasonal variation in thermal sensitivity within North American bird species. Proceedings of the Royal Society B, 290(2010), 20231398.
Shifting in space and time under climate change
Using a novel approach we developed to estimate trends from citizen science data while accounting for human observer bias, we found that across hundreds of species of North American birds, most species experienced several degrees of warming over the past 20 years despite moving north, but movement was strongly associated with limiting exposure. Further work has revealed that most taxonomic groups have undergone elevational range shifts, especially in the tropics, while poleward shifts are exclusive to highly mobile birds and butterflies in temperate zones. In older work, we showed that phenological responses to climate change are inversely related to body mass and are more closely related to temperature change in temperate zones and precipitation in the subtropics.
Cohen, J. and Jetz, W. 2025. Geographic redistributions are insufficient to mitigate the erosion of species’ environmental niches. Nature Ecology & Evolution, 9, 1234–1244.
Cohen, J. and Jetz, W. 2023. Strategies of seasonal environmental niche tracking at hemispheric scale. Global Ecology and Biogeography, 32(9), 1549-1560.
Cohen, J., Lajeunesse, M., Rohr, J. 2018. A global synthesis of animal phenological responses to climate change. Nature Climate Change, 8, 224-228. PDF
Understanding biodiversity patterns at continental scales
We modeled the seasonal distributions of over 650 North American bird species to understand biodiversity patterns and further conservation efforts in conjunction with the 30x30 initiative to conserve 30% of land and water by 2030. Based off that work, we explored how coarse-resolution models bias biodiversity predictions in heterogenous regions and for habitat specialist species especially during the breeding season. In soon-to-be-published work, we are exploring how incorporating extreme weather risk in species distribution models influences distributional predictions at range edges as well as continental biodiversity predictions.
Cohen, J., Ellis-Soto, D., Sharma, S., La Sorte, F., Jetz, W. Extreme weather risk shrinks species’ range boundaries and alters biodiversity predictions. In revisions at Global Change Biology. Preprint.
Cohen, J. and Jetz, W. Fine-grain predictions are key to accurately represent continental-scale biodiversity patterns. Global Ecology and Biogeography, 34(1), e13934.
Cohen, J. *, Gabor, L.*, Moudry, V., Jetz, W. (*equal first authors). Assessing the applicability of binary land-cover variables to species distribution models across multiple grains. Landscape Ecology, 39(66)
Climate change influences outbreaks of deadly wildlife diseases
Climate change and emerging infectious diseases are two concurrent crises that are likely linked. Using both lab and field-collected data, we repeatedly found that cold-adapted wildlife hosts experienced greatest disease risk under unusually warm conditions, while warm-adapted hosts were at greatest risk when it was unusually cool. We extended this framework to predict disease outbreaks across a wide variety of wildlife species and project global shifts in wildlife disease risk under global change.
Cohen, J., Sauer, E.L., Santiago, O., Spencer, S., Rohr, J.R. 2020. Divergent impacts of warming weather on wildlife disease risk across climates. Science, 370, eabb1702. PDF
Cohen, J., McMahon, T., Ramsay, C... [additional authors] 2019. Impacts of thermal mismatches on disease prevalence are moderated by life stage, body size, elevation, and latitude. Ecology Letters, 22(5), 817-825. PDF
Cohen, J., Civitello, D., Venesky, M., McMahon, T., Rohr, J.R. 2019. An interaction between climate change and infectious disease drove widespread amphibian declines. Global Change Biology, 25(3), 927-937. PDF
Cohen, J., Venesky, M., Sauer, E., Civitello, D., McMahon, T., Roznik, B., Rohr, J. 2017. The thermal mismatch hypothesis explains outbreaks of an emerging infectious disease. Ecology Letters, 20 (2), 184-193. PDF