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David Wahl

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

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Sediment cores collected in Guatemala

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...
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Climate Research and Development Program, Geology, Minerals, Energy, and Geophysics Science Center
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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...
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Filter Total Items: 20

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
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Climate Research and Development Program, Geology, Minerals, Energy, and Geophysics Science Center

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
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Geology, Minerals, Energy, and Geophysics Science Center

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
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Climate Research and Development Program, Geology, Minerals, Energy, and Geophysics Science Center

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
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Climate Research and Development Program, Geology, Minerals, Energy, and Geophysics Science Center

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 209 terrestrial and marine sites, including 382 individual proxy records. The records span at least 4000 of the last 12 0
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Climate Research and Development Program, Geology, Minerals, Energy, and Geophysics Science Center

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
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Climate Research and Development Program, Geology, Minerals, Energy, and Geophysics Science Center

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,
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Climate Research and Development Program, Geology, Minerals, Energy, and Geophysics Science Center

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
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Climate Research and Development Program, Geology, Minerals, Energy, and Geophysics Science Center

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
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Climate Research and Development Program, Geology, Minerals, Energy, and Geophysics Science Center

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
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Water Resources, 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
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Energy and Minerals, Climate Research and Development Program, Energy Resources Program, Groundwater and Streamflow Information Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Geology, Minerals, Energy, and Geophysics Science Center

Holocene environmental changes inferred from biological and sedimentological proxies in a high elevation Great Basin lake in the northern Ruby Mountains, Nevada, USA

Multi-proxy analyses were conducted on a sediment core from Favre Lake, a high elevation cirque lake in the northern Ruby Mountains, Nevada, and provide a ca. 7600 year record of local and regional environmental change. Data indicate that lake levels were lower from 7600-5750 cal yr BP, when local climate was warmer and/or drier than today. Effective moisture increased after 5750 cal yr BP and rem
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Energy and Minerals, Climate Research and Development Program, Energy Resources Program, Groundwater and Streamflow Information Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Geology, Minerals, Energy, and Geophysics Science Center

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.

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Sediment cores provide evidence of total warfare among the Classic Maya

This article is part of the Spring 2020 issue of the Earth Science Matters Newsletter.

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A 7,600-year record of climate and vegetation change from the northern Ruby Mountains, Nevada, USA

This article is part of the Fall 2015 issue of the Earth Science Matters Newsletter. 

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