David is a research scientist at the Geology, Minerals, Energy, and Geophysics Science Center. He received a PhD in Geography from UC Berkeley in 2005. Since joining the USGS in 2004, he has worked to understand drivers and impacts of Quaternary environmental change in North America. Now, his research focuses on reconstructing climate and anthropogenic environmental change.
After coming to the Menlo Park office of GMEG In 2004, David is currently focused on reconstructing climate and anthropogenic environmental change in the western US, Guatemala, and the central Pacific.
Professional Experience
2004 - Present, Research Geographer, US Geological Survey, Menlo Park, CA
2011 - Present, Assistant Adjunct Professor, Geography Department, UC Berkeley
Education and Certifications
Ph.D., Geography, University of California, Berkeley, 2005
M.A., Geography, University of California, Berkeley, 2000
B.A., History, Cal Poly, San Luis Obispo, 1996
Science and Products
Drivers and Impacts of North Pacific Climate Variability
Climate model forecasts indicate an increase in extreme hydrologic events, including floods and droughts, for California and the western U.S. in the future. To better understand what the consequences of this future change in climate may be, USGS scientists are studying the frequency, magnitude, and impacts of past hydroclimate variability and extremes in the region. This project produces well...
Filter Total Items: 21
Independent age estimates resolve the controversy of ancient human footprints at White Sands
Human footprints at White Sands National Park, New Mexico, USA, reportedly date to between ~23,000 and 21,000 years ago according to radiocarbon dating of seeds from the aquatic plant Ruppia cirrhosa. These ages remain controversial because of potential old carbon reservoir effects that could compromise their accuracy. We present new calibrated 14C ages of terrestrial pollen collected from the sam
Authors
Jeffrey S. Pigati, Kathleen B. Springer, Jeffrey S. Honke, David Wahl, Marie Rhondelle Champagne, Susan R.H. Zimmerman, Harrison J. Gray, Vincent L. Santucci, Daniel Odess, David Bustos, Matthew R. Bennett
Assessing reproducibility in sedimentary macroscopic charcoal count data
Current understanding of global late Quaternary fire history is largely drawn from sedimentary charcoal data. Since publication, CharAnalysis increasingly has been relied upon as a robust method for analyzing these data. However, several underlying assumptions of the algorithm have not been tested. This study uses replicated charcoal count data to examine the assumption of Poisson distribution and
Authors
Lysanna Anderson, Liubov S. Presnetsova, David Wahl, Geoffrey Phelps, Alan Gous
Methods for robust estimates of tree biomass from pollen accumulation rates: Quantifying paleoecological reconstruction uncertainty
Pollen accumulation rates (PAR, grains cm–2 year–1) have been shown to be a reliable but methodologically complex bioproxy for quantitative reconstruction of past tree abundance. In a prior study, we found that the PARs of major tree taxa – Pseudotsuga, Pinus, Notholithocarpus, and the pollen group TC (Taxaceae and Cupressaceae families) – were robust and precise estimators of contemporary tree bi
Authors
Clarke Alexandra Knight, John J. Battles, M. Jane Bunting, Marie Rhondelle Champagne, James A. Wanket, David Wahl
Land management explains major trends in forest structure and composition over the last millennium in California’s Klamath Mountains
For millennia, forest ecosystems in California have been shaped by fire from both natural processes and Indigenous land management, but the notion of climatic variation as a primary controller of the pre-colonial landscape remains pervasive. Understanding the relative influence of climate and Indigenous burning on the fire regime is key because contemporary forest policy and management are informe
Authors
Clarke Alexandra Knight, Lysanna Anderson, M. Jane Bunting, Marie Rhondelle Champagne, Rosie M. Clayburn, Jeffrey N. Crawford, Anna Klimaszewski-Patterson, Eric E. Knapp, Frank K. Lake, Scott A. Mensing, David Wahl, James Wanket, Alex Watts-Tobin, Matthew D. Potts, John J. Battles
Understanding rates of change: A case study using fossil pollen records from California to assess the potential for and challenges to a regional data synthesis
Insights into the rates at which ecosystems and vegetation respond to a changing climate is fundamental to anticipating impacts of projected climate change. Characterization of vegetation change over millennia to centuries has potential to make an important contribution toward this goal, and regional scale syntheses of fossil pollen data can provide the foundation for this understanding. However,
Authors
Lysanna Anderson, David Wahl, T. Bhattacharya
Linking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA
Quantitative reconstructions of vegetation abundance from sediment-derived pollen systems provide unique insights into past ecological conditions. Recently, the use of pollen accumulation rates (PAR, grains cm−2 year−1) has shown promise as a bioproxy for plant abundance. However, successfully reconstructing region-specific vegetation dynamics using PAR requires that accurate assessments of pollen
Authors
Clarke A. Knight, Mark Baskaran, M. Jane Bunting, Marie Rhondelle Champagne, Matthew D. Potts, David Wahl, James Wanket, John J. Battles
A multiproxy database of western North American Holocene paleoclimate records
Holocene climate reconstructions are useful for understanding the diverse features and spatial heterogeneity of past and future climate change. Here we present a database of western North American Holocene paleoclimate records. The database gathers paleoclimate time series from 184 terrestrial and marine sites, including 381 individual proxy records. The records span at least 4000 of the last 12 0
Authors
Cody C. Routson, Darrell S. Kaufman, Nicholas P. McKay, Michael Erb, S. H. Arcusa, Kendrick Brown, Matthew E. Kirby, Jeremiah Marsicek, R. Scott Anderson, Gonzalo Jimenez-Moreno, Jessica R. Rodysill, M. S. Lachniet, Sherilyn C. Fritz, Joseph Bennett, Michelle F. Goman, Sarah E. Metcalfe, J. M. Galloway, G. Schoups, David Wahl, Jesse L. Morris, F. Staines-Urias, A. Dawson, B. N. Shuman, Daniel G. Gavin, Jeffrey S. Munroe, Brian F. Cumming
Holocene paleoclimate change in the western US: The importance of chronology in discerning patterns and drivers
Sediment in lakes and meadows forms a powerful archive that can be used to reconstruct environmental change through time. Reconstructions of lake level, of chemical, biological, and hydrological conditions, and of surrounding vegetation provide detailed information about past climate conditions, both locally and regionally. Indeed, most of our current knowledge of centennial- to millennial-scale c
Authors
Susan Zimmerman, David Wahl
Radiocarbon and geologic evidence reveal Ilopango volcano as source of the colossal 'mystery' eruption of 539/40 CE
Ilopango volcano (El Salvador) erupted violently during the Maya Classic Period (250–900 CE) in a densely-populated and intensively-cultivated region of the southern Maya realm, causing regional abandonment of an area covering more than 20,000 km2. However, neither the regional nor global impacts of the Tierra Blanca Joven (TBJ) eruption in Mesoamerica have been well appraised due to limitations i
Authors
Robert A. Dull, John R. Southon, Steffen Kutterolf, Kevin J. Anchukaitis, Armin Freundt, David Wahl, Payson Sheets, Paul Amaroli, Walter Hernandez, Micheal C. Weimann, Clive Oppenheimer
Paleoenvironmental, epigraphic, and archaeological evidence of total warfare among the Classic Maya
Despite over a century of archaeological research, the nature and broader consequences of Classic Maya warfare remain poorly understood. Based on frequent epigraphic references and iconographic themes, Classic period (250-950 CE) Maya warfare has largely been viewed as ritualized and limited in scope. Evidence of warfare in the Terminal Classic period (TCP, 800-950 CE) is interpreted as an escalat
Authors
David Wahl, Lysanna Anderson, Francisco Estrada-Belli, Alexandre Tokovinine
A North American Hydroclimate Synthesis (NAHS) of the Common Era
This study presents a synthesis of century-scale hydroclimate variations in North America for the Common Era (last 2000 years) using new age models of previously published multiple proxy-based paleoclimate data. This North American Hydroclimate Synthesis (NAHS) examines regional hydroclimate patterns and related environmental indicators, including vegetation, lake water elevation, stream flow and
Authors
Jessica R. Rodysill, Lesleigh Anderson, Thomas M. Cronin, Miriam C. Jones, Robert S. Thompson, David B. Wahl, Debra A. Willard, Jason A. Addison, Jay R. Alder, Katherine H. Anderson, Lysanna Anderson, John A. Barron, Christopher E. Bernhardt, Steven W. Hostetler, Natalie M. Kehrwald, Nicole Khan, Julie N. Richey, Scott W. Starratt, Laura E. Strickland, Michael Toomey, Claire C. Treat, G. Lynn Wingard
By
Water Resources Mission Area, Climate Research and Development Program, Energy Resources Program, Groundwater and Streamflow Information Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Florence Bascom Geoscience Center, Geology, Minerals, Energy, and Geophysics Science Center, Geosciences and Environmental Change Science Center, St. Petersburg Coastal and Marine Science Center
Holocene climate variability and anthropogenic impacts from Lago Paixban, a perennial wetland in Peten, Guatemala
Analyses of an ~ 6 m sediment core from Lago Paixban in Peten, Guatemala, document the complex evolution of a perennial wetland over the last 10,300 years. The basal sediment is comprised of alluvial/colluvial fill deposited in the early Holocene. The absence of pollen and gastropods in the basal sediments suggests intermittently dry conditions until ~ 9000 cal yr. BP (henceforth BP) when the basi
Authors
David B. Wahl, Richard D. Hansen, Roger Byrne, Lysanna Anderson, T. Schreiner
Non-USGS Publications**
Hansen, R., S. Bozarth, J. Jacob, Wahl D. and T. Schreiner (2002) “Climatic and Environmental Variability in the Rise of Maya Civilization.” Ancient Mesoamerica 13: 273-295.
Wahl, D., R. Byrne, T. Schreiner and R. Hansen (2006) “Holocene Vegetation Change in the Northern Peten and its Implications for Maya Prehistory.” Quaternary Research 65:380-389.
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
- Science
Drivers and Impacts of North Pacific Climate Variability
Climate model forecasts indicate an increase in extreme hydrologic events, including floods and droughts, for California and the western U.S. in the future. To better understand what the consequences of this future change in climate may be, USGS scientists are studying the frequency, magnitude, and impacts of past hydroclimate variability and extremes in the region. This project produces well... - Publications
Filter Total Items: 21
Independent age estimates resolve the controversy of ancient human footprints at White Sands
Human footprints at White Sands National Park, New Mexico, USA, reportedly date to between ~23,000 and 21,000 years ago according to radiocarbon dating of seeds from the aquatic plant Ruppia cirrhosa. These ages remain controversial because of potential old carbon reservoir effects that could compromise their accuracy. We present new calibrated 14C ages of terrestrial pollen collected from the samAuthorsJeffrey S. Pigati, Kathleen B. Springer, Jeffrey S. Honke, David Wahl, Marie Rhondelle Champagne, Susan R.H. Zimmerman, Harrison J. Gray, Vincent L. Santucci, Daniel Odess, David Bustos, Matthew R. BennettAssessing reproducibility in sedimentary macroscopic charcoal count data
Current understanding of global late Quaternary fire history is largely drawn from sedimentary charcoal data. Since publication, CharAnalysis increasingly has been relied upon as a robust method for analyzing these data. However, several underlying assumptions of the algorithm have not been tested. This study uses replicated charcoal count data to examine the assumption of Poisson distribution andAuthorsLysanna Anderson, Liubov S. Presnetsova, David Wahl, Geoffrey Phelps, Alan GousMethods for robust estimates of tree biomass from pollen accumulation rates: Quantifying paleoecological reconstruction uncertainty
Pollen accumulation rates (PAR, grains cm–2 year–1) have been shown to be a reliable but methodologically complex bioproxy for quantitative reconstruction of past tree abundance. In a prior study, we found that the PARs of major tree taxa – Pseudotsuga, Pinus, Notholithocarpus, and the pollen group TC (Taxaceae and Cupressaceae families) – were robust and precise estimators of contemporary tree biAuthorsClarke Alexandra Knight, John J. Battles, M. Jane Bunting, Marie Rhondelle Champagne, James A. Wanket, David WahlLand management explains major trends in forest structure and composition over the last millennium in California’s Klamath Mountains
For millennia, forest ecosystems in California have been shaped by fire from both natural processes and Indigenous land management, but the notion of climatic variation as a primary controller of the pre-colonial landscape remains pervasive. Understanding the relative influence of climate and Indigenous burning on the fire regime is key because contemporary forest policy and management are informeAuthorsClarke Alexandra Knight, Lysanna Anderson, M. Jane Bunting, Marie Rhondelle Champagne, Rosie M. Clayburn, Jeffrey N. Crawford, Anna Klimaszewski-Patterson, Eric E. Knapp, Frank K. Lake, Scott A. Mensing, David Wahl, James Wanket, Alex Watts-Tobin, Matthew D. Potts, John J. BattlesUnderstanding rates of change: A case study using fossil pollen records from California to assess the potential for and challenges to a regional data synthesis
Insights into the rates at which ecosystems and vegetation respond to a changing climate is fundamental to anticipating impacts of projected climate change. Characterization of vegetation change over millennia to centuries has potential to make an important contribution toward this goal, and regional scale syntheses of fossil pollen data can provide the foundation for this understanding. However,AuthorsLysanna Anderson, David Wahl, T. BhattacharyaLinking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA
Quantitative reconstructions of vegetation abundance from sediment-derived pollen systems provide unique insights into past ecological conditions. Recently, the use of pollen accumulation rates (PAR, grains cm−2 year−1) has shown promise as a bioproxy for plant abundance. However, successfully reconstructing region-specific vegetation dynamics using PAR requires that accurate assessments of pollenAuthorsClarke A. Knight, Mark Baskaran, M. Jane Bunting, Marie Rhondelle Champagne, Matthew D. Potts, David Wahl, James Wanket, John J. BattlesA multiproxy database of western North American Holocene paleoclimate records
Holocene climate reconstructions are useful for understanding the diverse features and spatial heterogeneity of past and future climate change. Here we present a database of western North American Holocene paleoclimate records. The database gathers paleoclimate time series from 184 terrestrial and marine sites, including 381 individual proxy records. The records span at least 4000 of the last 12 0AuthorsCody C. Routson, Darrell S. Kaufman, Nicholas P. McKay, Michael Erb, S. H. Arcusa, Kendrick Brown, Matthew E. Kirby, Jeremiah Marsicek, R. Scott Anderson, Gonzalo Jimenez-Moreno, Jessica R. Rodysill, M. S. Lachniet, Sherilyn C. Fritz, Joseph Bennett, Michelle F. Goman, Sarah E. Metcalfe, J. M. Galloway, G. Schoups, David Wahl, Jesse L. Morris, F. Staines-Urias, A. Dawson, B. N. Shuman, Daniel G. Gavin, Jeffrey S. Munroe, Brian F. CummingHolocene paleoclimate change in the western US: The importance of chronology in discerning patterns and drivers
Sediment in lakes and meadows forms a powerful archive that can be used to reconstruct environmental change through time. Reconstructions of lake level, of chemical, biological, and hydrological conditions, and of surrounding vegetation provide detailed information about past climate conditions, both locally and regionally. Indeed, most of our current knowledge of centennial- to millennial-scale cAuthorsSusan Zimmerman, David WahlRadiocarbon and geologic evidence reveal Ilopango volcano as source of the colossal 'mystery' eruption of 539/40 CE
Ilopango volcano (El Salvador) erupted violently during the Maya Classic Period (250–900 CE) in a densely-populated and intensively-cultivated region of the southern Maya realm, causing regional abandonment of an area covering more than 20,000 km2. However, neither the regional nor global impacts of the Tierra Blanca Joven (TBJ) eruption in Mesoamerica have been well appraised due to limitations iAuthorsRobert A. Dull, John R. Southon, Steffen Kutterolf, Kevin J. Anchukaitis, Armin Freundt, David Wahl, Payson Sheets, Paul Amaroli, Walter Hernandez, Micheal C. Weimann, Clive OppenheimerPaleoenvironmental, epigraphic, and archaeological evidence of total warfare among the Classic Maya
Despite over a century of archaeological research, the nature and broader consequences of Classic Maya warfare remain poorly understood. Based on frequent epigraphic references and iconographic themes, Classic period (250-950 CE) Maya warfare has largely been viewed as ritualized and limited in scope. Evidence of warfare in the Terminal Classic period (TCP, 800-950 CE) is interpreted as an escalatAuthorsDavid Wahl, Lysanna Anderson, Francisco Estrada-Belli, Alexandre TokovinineA North American Hydroclimate Synthesis (NAHS) of the Common Era
This study presents a synthesis of century-scale hydroclimate variations in North America for the Common Era (last 2000 years) using new age models of previously published multiple proxy-based paleoclimate data. This North American Hydroclimate Synthesis (NAHS) examines regional hydroclimate patterns and related environmental indicators, including vegetation, lake water elevation, stream flow andAuthorsJessica R. Rodysill, Lesleigh Anderson, Thomas M. Cronin, Miriam C. Jones, Robert S. Thompson, David B. Wahl, Debra A. Willard, Jason A. Addison, Jay R. Alder, Katherine H. Anderson, Lysanna Anderson, John A. Barron, Christopher E. Bernhardt, Steven W. Hostetler, Natalie M. Kehrwald, Nicole Khan, Julie N. Richey, Scott W. Starratt, Laura E. Strickland, Michael Toomey, Claire C. Treat, G. Lynn WingardByWater Resources Mission Area, Climate Research and Development Program, Energy Resources Program, Groundwater and Streamflow Information Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Florence Bascom Geoscience Center, Geology, Minerals, Energy, and Geophysics Science Center, Geosciences and Environmental Change Science Center, St. Petersburg Coastal and Marine Science CenterHolocene climate variability and anthropogenic impacts from Lago Paixban, a perennial wetland in Peten, Guatemala
Analyses of an ~ 6 m sediment core from Lago Paixban in Peten, Guatemala, document the complex evolution of a perennial wetland over the last 10,300 years. The basal sediment is comprised of alluvial/colluvial fill deposited in the early Holocene. The absence of pollen and gastropods in the basal sediments suggests intermittently dry conditions until ~ 9000 cal yr. BP (henceforth BP) when the basiAuthorsDavid B. Wahl, Richard D. Hansen, Roger Byrne, Lysanna Anderson, T. SchreinerNon-USGS Publications**
Hansen, R., S. Bozarth, J. Jacob, Wahl D. and T. Schreiner (2002) “Climatic and Environmental Variability in the Rise of Maya Civilization.” Ancient Mesoamerica 13: 273-295.Wahl, D., R. Byrne, T. Schreiner and R. Hansen (2006) “Holocene Vegetation Change in the Northern Peten and its Implications for Maya Prehistory.” Quaternary Research 65:380-389.**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
- News