I am a palynologist (pollen and spores) with expertise in paleoecology, paleoclimatology, and biostratigraphy. My biostratigraphic expertise extends from the Carboniferous to the Holocene, with an emphasis on Euramerica (Paleozoic) and the Northern Hemisphere. My paleoclimate expertise includes the late Paleozoic and the Paleogene to Holocene intervals.
Editorial Boards
- Global and Planetary Change
- Frontiers in Ecology and Evolution – Paleoecology section Review Editor
- Quaternary
- Review of Palaeobotany and Palynology
Professional Experience
2021-Present Research Geologist, US Geological Survey, Reston, Virginia
2011-2021 Coordinator, USGS Climate Research & Development Program
1991-2011 Research Geologist, US Geological Survey, Reston, Virginia
1990-1991 Postdoctoral Researcher, National Museum of Natural History, Smithsonian Institution, Washington, DC
Education and Certifications
University of Illinois at Urbana-Champaign - Ph.D., Botany 1990
University of Illinois at Urbana-Champaign - M.S., Botany 1985
The Pennsylvania State University - B.S., Botany 1982
Stephens College - A.A., Geology 1980
Affiliations and Memberships*
American Geophysical Union
Geological Society of America
The Palynological Society
Science and Products
Broadening the perspectives of sedimentary organic matter analysis to understand Earth system response to change
Roles of climatic and anthropogenic factors in shaping Holocene vegetation and fire regimes in Great Dismal Swamp, eastern USA
Regional variability in peatland burning at mid-to high-latitudes during the Holocene
Pollen records, postglacial: Southeastern North America
Poleward amplification, seasonal rainfall and forest heterogeneity in the Miocene of the eastern USA
A 1.8 million year history of Amazon vegetation
Biostratigraphically significant palynofloras from the Paleocene–Eocene boundary of the USA
Foreword: Wetland carbon and environmental management
Tidal erosion and upstream sediment trapping modulate records of land-use change in a formerly glaciated New England estuary
Application of a regional climate model to assess changes in the climatology of the Eastern US and Cuba associated with historic landcover change
Paleoclimate of the subtropical Andes during the latest Miocene, Lauca Basin, Chile
Rapid inundation of the southern Florida coastline despite low relative sea-level rise rates during the late-Holocene
Broader view of North American climate over the past two millennia: Synthesizing paleoclimate records from diverse archives
Charcoal data from four sites in Great Dismal Swamp National Wildlife Refuge - August 2022
Radiocarbon dates, charcoal, and polycyclic aromatic hydrocarbon (PAH) data from Great Dismal Swamp Sites GDS-519 and GDS-520
Science and Products
- Publications
Filter Total Items: 99
Broadening the perspectives of sedimentary organic matter analysis to understand Earth system response to change
This paper broadens the description of sedimentary organic matter from the conventional use of coal petrography to include palynological and geochemical sedimentary organic matter. Palynological sedimentary organic matter includes all chemically resistant organic microfossils, such as pollen and spores, dinocysts, microforaminifera (chitinoid-like linings of foraminifera), microscopic algae, charcAuthorsDebra A. Willard, Leslie F. RuppertRoles of climatic and anthropogenic factors in shaping Holocene vegetation and fire regimes in Great Dismal Swamp, eastern USA
The Great Dismal Swamp wetland, spanning >400 km2 along the Virginia and North Carolina border, was shaped by a complex combination of geomorphic, climatic, and anthropogenic forcings during the last 14,000 years. Pollen, macrofossils, charcoal, and physical properties from sediment cores at seven sites provide a detailed record of the spatial heterogeneity of the wetland and the roles played by nAuthorsDebra A. Willard, Miriam C. Jones, Jay R. Alder, David Fastovich, Kristen Hoefke, Robert Poirier, Fred C. WursterRegional variability in peatland burning at mid-to high-latitudes during the Holocene
Northern peatlands store globally-important amounts of carbon in the form of partly decomposed plant detritus. Drying associated with climate and land-use change may lead to increased fire frequency and severity in peatlands and the rapid loss of carbon to the atmosphere. However, our understanding of the patterns and drivers of peatland burning on an appropriate decadal to millennial timescale reAuthorsThomas G. Sim, Graeme T. Swindles, Paul J. Morris, Andy J. Baird, Angela V. Gallego-Sala, Yuwan Wang, Maarten Blaauw, Philip Camill, Michelle Garneau, Mark Hardiman, Julie Loisel, Minna Valiranta, Lysanna Anderson, Karina Apolinarska, Femke Augustijns, Liene Aunina, Joannie Beaulne, Přemysl Bobek, Werner Borken, Nils Broothaerts, Qiao-Yu Cui, Marissa A. Davies, Ana Ejarque, Michelle Farrell, Ingo Feeser, Angelica Feurdean, Richard Fewster, Sarah A. Finkelstein, Marie-José Gaillard, Mariusz Gałka, Annica Greisman, Liam Heffernan, Renske Hoevers, Miriam C. Jones, Teemu Juselius, Edgar Karofeld, Klaus Holger Knorr, Atte Korhola, Dmitri Kupriyanov, Malin Kylander, Terri Lacourse, Mariusz Lamentowicz, Martin Lavoie, Geoffrey Lemdahl, Dominika Łuców, Gabriel Magnan, Alekss Maksims, Claudia A. Mansilla, Katarzyna Marcisz, Elena Marinova, Paul J.H. Mathijssen, Dmitri Mauquoy, Yuri Mazei, Natalia Mazei, Julia McCarroll, Robert McCulloch, Alice Milner, Yannick Miras, Fraser J.G. Mitchell, Elena Novenko, Nicolas Pelletier, Matthew Peros, Sanna Pillo, Louis-Martin Pilote, Guillaume Primeau, Damien Rius, Vincent Robin, Mylène Robitaille, Thomas P. Roland, Eleonor Ryberg, A. Britta K. Sannel, Karsten Schittek, Gabriel Servera-Vives, William Shotyk, Michał Słowiński, Normunds Stivrins, Ward Swinnen, Gareth Thompson, Alexei Tiunov, Andrey N. Tsyganov, Eeva-Stiina Tuittila, Gert Verstraeten, Tuomo Wallenius, Julia Webb, Debra A. Willard, Zicheng Yu, Claudio Zaccone, Hui ZhangPollen records, postglacial: Southeastern North America
Pollen records from the unglaciated southeastern region of North America provide an overview of biogeographic changes associated with vegetational migration northward following the retreat of the Laurentide Ice Sheet. Changing insolation during the Holocene affected forest composition on the Coastal Plain, and rising sea level controlled the distribution of marsh and forested wetlands throughout tAuthorsDebra A. WillardPoleward amplification, seasonal rainfall and forest heterogeneity in the Miocene of the eastern USA
Paleoclimate reconstructions can provide a window into the environmental conditions in Earth history when atmospheric carbon dioxide concentrations were higher than today. In the eastern USA, paleoclimate reconstructions are sparse, because terrestrial sedimentary deposits are rare. Despite this, the eastern USA has the largest population and population density in North America, and understandingAuthorsTammo Reichgelt, Aly Baumgartner, Ran Feng, Debra A. WillardA 1.8 million year history of Amazon vegetation
During the Pleistocene, long-term trends in global climate were controlled by orbital cycles leading to high amplitude glacial-interglacial variability. The history of Amazonian vegetation during this period is largely unknown since no continuous record from the lowland basin extends significantly beyond the last glacial stage. Here we present a paleoenvironmental record spanning the last 1800 kyrAuthorsAndrea K. Kern, Thomas K. Akabane, Jaqueline Q. Ferreira, Cristiano M. Chiessi, Debra A. Willard, Fabricio Ferreira, Allan O. Sanders, Cleverson G. Silva, Catherine Rigsby, Francisco W. Cruz, Gary S. Dwyer, Sherilyn C. Fritz, Paul A. BakerBiostratigraphically significant palynofloras from the Paleocene–Eocene boundary of the USA
Pollen and spores were recovered from the Paleocene Fort Union Formation and Paleocene–Eocene Willwood Formation of the Bighorn Basin (BHB), northwestern Wyoming, USA. In many local stratigraphic sections in the BHB, the base of the Eocene has been identified by the characteristic negative carbon isotope excursion (CIE) that marks the beginning of the Paleocene–Eocene Thermal Maximum (PETM). The pAuthorsVera A. Korasidis, Scott L. Wing, Guy J. Harrington, Thomas Demchuk, J. Gfavendyck, Phillip E. Jardine, Debra A. WillardForeword: Wetland carbon and environmental management
No abstract available.AuthorsScott Covington, Debra A. WillardTidal erosion and upstream sediment trapping modulate records of land-use change in a formerly glaciated New England estuary
Land clearing, river impoundments, and other human modifications to the upland landscape and within estuarine systems can drive coastal change at local to regional scales. However, as compared with mid-latitude coasts, the impacts of human modifications along sediment-starved formerly glaciated coastal landscapes are relatively understudied. To address this gap, we present a late-Holocene record oAuthorsJustin L. Shawler, Christopher J. Hein, Elizabeth A Canuel, James M Kaste, Gregory G Fitzsimons, Ioannis Y. Georgiou, Debra A. WillardApplication of a regional climate model to assess changes in the climatology of the Eastern US and Cuba associated with historic landcover change
We examine the annual, seasonal, monthly, and diurnal climate responses to the land use change (LUC) in eastern United States and Cuba during four epochs (1650, 1850, 1920, and 1992) with ensemble simulations conducted with the RegCM4 regional climate model that includes the Biosphere Atmosphere Transfer Scheme (BATS1e) surface physics package (Dickinson et al., 1993). We derived the land use (LU)AuthorsSteven W. Hostetler, R Reker, Jay R. Alder, Thomas Loveland, Debra A. Willard, Christopher E. Bernhardt, Eric T. Sundquist, Renee L. ThompsonPaleoclimate of the subtropical Andes during the latest Miocene, Lauca Basin, Chile
Uplift of the Andean Cordillera during the Miocene and Pliocene produced large-scale changes in regional atmospheric circulation that impacted local ecosystems. The Lauca Basin (northern Chilean Altiplano) contains variably fluvial and lacustrine sedimentary sequences spanning the interval from 8.7 to 2.3 Ma. Field samples were collected from paleo-lacustrine sediments in the basin. Sediments wereAuthorsMelina Feitl, Andrea Kern, Amanda Jones, Sherilyn Fritz, Paul E. Baker, Joeckel . R.M., Wout Salenbien, Debra A. WillardRapid inundation of the southern Florida coastline despite low relative sea-level rise rates during the late-Holocene
Sediment cores from Florida Bay, Everglades National Park were examined to determine ecosystem response to relative sea-level rise (RSLR) over the Holocene. High-resolution multiproxy analysis from four sites show freshwater wetlands transitioned to mangrove environments 4–3.6 ka, followed by estuarine environments 3.4–2.8 ka, during a period of enhanced climate variability. We calculate a RSLR raAuthorsMiriam Jones, G. Lynn Wingard, Bethany Stackhouse, Katherine Keller, Debra A. Willard, Marci E. Marot, Bryan D. Landacre, Christopher E. Bernhardt - Science
Broader view of North American climate over the past two millennia: Synthesizing paleoclimate records from diverse archives
Regional- to continental-scale paleoclimate syntheses of temperature and hydroclimate in North America are essential for understanding long-term spatiotemporal variability in climate, and for properly assessing risk on decadal and longer timescales. However, existing syntheses rely almost exclusively on tree-ring records, which are known to underestimate low-frequency variability and rarely extend - Data
Charcoal data from four sites in Great Dismal Swamp National Wildlife Refuge - August 2022
Charcoal counts and radiocarbon dates from four sediment cores collected in Great Dismal Swamp in 2017 and 2018 were incorporated into a synthesis of charcoal records from northern hemisphere peatlands (Sims et al., in review). Macroscopic charcoal was counted in three size classes: 125-250 micrometers, and 250-500 micrometers, and >500 micrometers. Uncalibrated radiocarbon dates were obtained andRadiocarbon dates, charcoal, and polycyclic aromatic hydrocarbon (PAH) data from Great Dismal Swamp Sites GDS-519 and GDS-520
Sediment cores were collected in Great Dismal Swamp National Wildlife Refuge in November, 2017 to advance understanding of climate- and land-management driven changes in vegetation, hydrology, and fire regimes. Radiocarbon dates were obtained from samples in two cores (GDS-519-3-21-2017 and GDS-520-3-21-2017) to generate age models for the cores. Bulk sediment samples, charcoal, plant macrofossils - Multimedia
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*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government