Research

Biodiversity Change and Geologic Signals of the Anthropocene

Anthropogenic activities changed our planet over the course of the Holocene, but the scale of human impacts increased dramatically around the mid-20th century, representing the start of the Anthropocene. Global signals of these impacts and the resulting biotic and abiotic changes are captured in the geologic record. These pervasive anthropogenic impacts, including pollution, road-building, the rise of plastics, etc., are comparable in magnitude, uniqueness, and geologic longevity to global changes that mark previous major geologic time intervals. To identify global and local geological signals that can be used to characterize the Anthropocene, we are examining sediment cores from Searsville Lake, a 126-year-old reservoir located at Jasper Ridge in the eastern foothills of the San Francisco Peninsula.

  • Learn more about our project at the Jasper Ridge Biological Preserve website and blog
  • Articles in Nature News about the Anthropocene Working Group, including our work on Searsville Lake
    • “Humans versus Earth: the quest to define the Anthropocene” link

    • “Anthropocene now: influential panel votes to recognize Earth’s new epoch” link

  • Article on the Anthropocene Working Group in Suddeutsche Zeitung, “‘We need new systems of knowledge production’: In Berlin, scientists met to prove that the era of the ‘Anthropocene’ has begun.” link – pdf
  • Read our papers on signals of the Anthropocene in Searsville Lake (Stegner et al. 2023) and vegetation change in the Searsville Lake watershed (Anderson et al. 2023)

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) Abrupt changes in ecological systems: Inference and diagnosis. Trends in Ecology and Evolution. DOI: 10.1016/j.tree.2018.04.013 pdf – link
  • Intrinsic versus extrinsic drivers of abrupt Holocene Hemlock decline: Ramiadantsoa et al. (2019) The potential role of intrinsic processes in generating abrupt and synchronous tree declines during the Holocene. Ecology 100(2):e02579. DOI: 1002/ecy.2579 pdf – link – source code
  • Early warning signals of critical transitions in paleoecological time series: Stegner et al. (2019) Inferring critical transitions in paleoecological time series with irregular sampling and variable time-averaging. Quaternary Science Reviews 207: 49-63 DOI: 10.1016/j.quascirev.2019.01.009 pdf – link – source code
  • Do fires trigger abrupt changes in Northern Rockies forests during periods of climate change?: Stegner et al. (2019) Post-fire vegetation and climate dynamics in low-elevation forests over the last three millennia in Yellowstone National Park. Ecography 42:1226-1236 DOI: 10.1111/ecog.04445 link
  • Holocene resilience at the Midwest prairie-forest ecotone
  • Abrupt, community-level change in the Quaternary pollen record across North America Read more here

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. Deep time records 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.
  • Lessons for conservation from beneath the pavement: Read more here (Mychajliw et al. 2022) about how geohistorical data can inform conservation in novel ecosystems, like urban area.

Biogeography in western North America:

On-going 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 macroecological patterns through time; and 3) reveal how mammals have responded to environmental change.

Recent Posts