I study long-term diversity dynamics in order to understand the range of “normal” ecological fluctuation. Detailed historic and paleoecological records can be used to characterize these past long-term ecological dynamics, and to predict how species and ecosystems will respond to future change.
Abrupt Change in Ecological Systems:
How, when, and why do abrupt changes and ecological regime shifts occur? Using the extensive North American pollen record, I am applying and developing techniques to identify abrupt change in vegetation. Visit the ACES project website to learn more. Specific projects include:
- Framework for diagnosing abrupt changes: (Ratajczak et al 2018 TREE Abrupt Change in Ecological Systems: Inference and Diagnosis)
- Intrinsic versus extrinsic drivers of abrupt Holocene Hemlock decline (Ramiadantsoa et al., in press, The potential role of intrinsic processes in generating abrupt and quasi-synchronous tree declines during the Holocene. Ecology)
- Early warning signals of critical transitions in paleoecological time series (Stegner et al., in press, Inferring critical transitions in paleoecological time series with irregular sampling and variable time-averaging. Quaternary Science Reviews)
- Holocene resilience at the Midwest prairie-forest ecotone
- Abrupt, community-level change in the Quaternary pollen record across North America
Conservation in a rapidly changing world:
We know from the fossil record that ecosystems are constantly in flux. However, rates of global change today are unprecedented and, among many negative outcomes, we face the likely possibility of major extinction. Paleontology can help to provide context and insight for today’s conservation challenges.
- A new conservation paradigm: Generalizable conservation insights from the fossil record; Read the Conservation Paleobiology working group publication in Science here.
Paleo biogeography in western North America:
On-going paleoecological research on the Colorado Plateau is designed to 1) expand our knowledge of the Quaternary small vertebrates, a group under-studied in this region; 2) uncover paleo macroecological patterns and relate those to modern systems; 3) develop new techniques for identifying Quaternary vertebrate fossils; and 4) reveal how small mammals have responded to previous episodes of environmental change.
- Mescal Cave, Mojave Desert (Stegner 2015, Quaternary Research)
- Small mammals of southeastern Utah over the last 5,000 years: new excavations (Stegner 2016, The Holocene)
- Ecometrics: Mammalian functional group diversity dynamics (Stegner and Holmes 2013, Paleo3)
- Bears Ears National Monument: this region is an unparalleled resource for studying the history of life on earth since the Permian. I conduct fossil surveys, excavations, and small mammal surveys in the Bears Ears. Read more on my Teaching and Outreach page.
Colorado Plateau modern & historical biogeography:
I use a combination of mark-recapture surveys and data mining to understand modern mammal diversity patterns on local and regional scales, and to address questions like: How are species distributed across the landscape? Does abundance relate to environmental factors, intrinsic factors, or both? How do local diversity and abundance relate to regional patterns? And how does the modern compare to the fossil?
- Modern vs. historical biogeography of Colorado Plateau National Parks (Stegner et al. 2017)