About

Kenzie Johnston is an Assistant Professor - Professional Practice and the Director of the Master in Plant Health Management (MPHM) program at Ohio State University. His role involves overseeing the program and contributing to the field of entomology through professional practice. The page does not provide specific details about his research focus, background, or key contributions, only his title and administrative role.

Research topics

• Biology
• Physical geography
• Ecology
• Geography
• Demography
• Environmental science
• Geology
• Archaeology

Selected publications

• Evidence for highly variable land use but a stable climate in the southwest Maya lowlands

  2025-07-14

  preprintOpen accessCorresponding

  Abstract. The lowland Maya of Mesoamerica were affected by multiple environmental stresses throughout their history, and are experienced a major demographic and political decline, or collapse, during a period of inferred intense multidecadal drought, between approximately 1200- and 1000-years BP. The complex interactions between climate and society in the Maya lowlands are generally not well understood. We combine carbon and hydrogen isotopic analyses of leaf wax n-alkanes with quantification of faecal stanols and polycyclic aromatic hydrocarbons from a lake sediment core from the southwest lowlands to assess whether 1) palaeoecological evidence of land use is related to population change; and 2) whether population and land use are linked to changing precipitation. Our data reveal a transition from generally more intense fire use and C4 plant agriculture during the Preclassic (3500–2000 BP) to dense populations and reduced fire use during the Classic (1600–1000 BP). This is consistent with other evidence for a more urbanised and specialised society in the Classic. We do not find evidence for drought in the hydrogen isotope leaf wax record (δDlw), implying that local drought was not a primary driver of observed variability in land use or population change.

  PublisherDOI

• Evidence for highly variable land use but a stable climate in the southwest Maya lowlands

  Biogeosciences · 2025-11-21

  articleOpen accessCorresponding

  Abstract. The lowland Maya of Mesoamerica were affected by multiple environmental stresses throughout their history, and many experienced a major demographic and political decline, or collapse, during a period of inferred intense multidecadal drought, approximately 1200- and 1000-years BP. Given regional variation in the timing and character of the collapse (Demarest, 2004; Hodell et al., 2007; Webster et al., 2007; Kennett and Beach, 2014; Douglas et al., 2015), much remains to be discovered about the complex interactions between climate and society in the Maya lowlands. To this end, we combine carbon and hydrogen isotopic analyses of leaf wax n-alkanes with quantification of faecal stanols and polycyclic aromatic hydrocarbons from a lake sediment core from the southwest lowlands to assess whether (1) palaeoecological evidence of land use is related to population change; and (2) whether population and land use are linked to changing precipitation. Our data reveal a transition from generally more intense fire use and C4 plant agriculture during the Preclassic (3500–2000 BP) to dense populations and reduced fire use during the Classic (1600–1000 BP). This is consistent with other evidence for a more urbanised and specialised society in the Classic. We do not find evidence of drought in the hydrogen isotope leaf wax record (δDlw), implying that local drought was not a primary driver of observed variability in land use or population change in the Classic-period southwestern lowlands.

  PublisherOA PDFDOI

• Climate linkages between fire, population, and agriculture in the Maya lowlands

  2022 · 1 citations

  • Ecology
  • Geography
  • Environmental science

  <p>Understanding past societal responses to climate change requires proxy indicators of human population, climate and land-use change. We apply a range of proxies to a lake sediment core from Laguna Itzan, a cenote adjacent to the ancient Maya population centre of Itzan, in order to examine the response of the lowland Maya to climatic and environmental change, which remains poorly understood. By combining molecular proxies for population (faecal stanols) and biomass burning (polycyclic aromatic hydrocarbons or PAHs) with isotopic analyses of plant wax n-alkanes as proxies for vegetation change (δ<sup>13</sup>C) and palaeohydrology (δ<sup>2</sup>H), we show the complex interplay of environmental and societal changes over 3300 years.</p><p>Leaf wax hydrogen isotope records show that drought between ca. 750 and 900 CE, thought to have been responsible for societal collapse or transformation across the Maya lowlands, is not expressed in the catchment of Itzan. This likely reflects spatial variability in the magnitude and timing of climate change. Population decline at Itzan may have been a result of instability caused by drought from other areas as a result of military incursions or through climate migration/an influx of climate refugees, pressures between neighbouring polities, or disruptions to trade networks or regional food production systems.</p><p>Leaf wax carbon isotope ratios indicate brief intervals of intensive maize agriculture, generally associated with wet periods, but this expansion of maize agriculture is not long lasting, and often returns to baseline levels of C<sub>4</sub> plant abundance. In addition to the earlier presence of humans at this site than currently indicated in the Itzan archaeological record based on the abundance of faecal stanols, we infer cultivation of maize around 4000 year BP, and potentially earlier. Further, analysis of the distribution of polycyclic aromatic hydrocarbons suggests that fire in the catchment transitioned over the past 3500 years from intense fires associated with slash and burn, or swidden, agriculture to a less intense fire regime following initial land clearance.</p><p>Our data indicate that human population dynamics and patterns of land clearance for agriculture varied substantially throughout the sediment core record, and that palaeoclimatic change may have driven these patterns. </p>

  PublisherDOI

• Molecular evidence for human population change associated with climate events in the Maya lowlands

  Quaternary Science Reviews · 2021 · 29 citations

  • Geography
  • Archaeology
  • Ecology

  The analysis of faecal stanols in lake sediment cores offers a novel opportunity to reconstruct human population change, assuming that variability in faecal stanol concentration is a reliable proxy for relative human populations. The ancient lowland Maya of Mesoamerica represents an important ancient society whose demographic dynamics in many locations remain uncertain. We apply the faecal stanol proxy to a sediment core retrieved from a lake adjacent to the archaeological site of Itzan, an ancient population centre in the southwestern Maya lowlands. The sedimentary faecal stanol record from Laguna Itzan implies substantial centennial- and millennial-scale changes in local human populations from 3300 cal years BP to the present. Variability in faecal stanol concentrations is broadly consistent with archaeological evidence for regional societal change across the Maya lowlands, but also implies an earlier presence of humans at this site than is currently indicated in the Itzan archaeological record. We find evidence for high-frequency variability in coprostanol concentrations during the Maya Preclassic period, which we infer represents centennial-scale shifts in settlement patterns associated with changes in agricultural and land use patterns. Given Preclassic-period faecal peak stanol concentrations, we observe lower-than-expected Classic-period faecal peak stanol concentrations, and these may partly be a result of either use of human waste for fertiliser or reduced soil erosion or both. Three periods of inferred population decline are associated with palaeoclimate evidence for a drying climate, specifically during the Terminal Classic (1220-1050 cal yr BP) and the Protoclassic 2 (1860-1670 cal yr BP), as well as the less well-studied drought between 3330 and 2900 cal yr BP during the Early to Middle Preclassic periods. An additional decline and hiatus in coprostanol input coincides with a period of anomalously wet climate in the Late Preclassic. These linkages suggest that climatic change and variability could have played a role in demographic change at multiple points in the evolution of Maya civilisation. Our work shows that faecal stanols are valuable proxies for past human population dynamics, and their relation to climatic change, in Mesoamerica.

  PublisherDOI

• Determining the controls on faecal stanol concentrations and ratios in tropical lake sediments

  2019

  • Environmental science
  • Ecology
  • Physical geography

  Faecal stanols offer an exciting opportunity to determine population change in the past but the controls of their concentrations and ratios within lake sediments are not well understood. We present the variability in stanol concentrations and ratios from lakes across environmental gradients, both between and in lakes across climatic and land-use gradients in Mexico, Guatemala, and Belize in order to determine the factors controlling preservation and degradation in lacustrine sediments. We also measured physical properties of lakes such as dissolved oxygen, pH, and water column temperature and estimated the approximate human population in each catchment, with the goal of producing a semi-quantitative calibration of human population to coprostanol+epi-coprostanol as a ratio to cholestanol, a more widely produced bacterial stanol. In particular we explore the hypothesis that a dominant control on concentrations and ratios is proximity to a human settlement. We evaluate this hypothesis in two lakes (L. Peten-Itza and L. Izabal) where we collected samples at varying distances from major population centres. This will have implications for the targeting of lake cores in studies where determining population change is the goal. In addition to this work we will share three intriguing preliminary palaeo-records of stanol concentrations from Guatemala (Laguna Itzan, Laguna Peten-Itza, and Lago Izabal). These records imply highly dynamic millennial scale changes in human populations, and we apply the modern sediment data to better constrain the interpretation of these data. Our work shows that faecal stanols have a strong potential as proxies for changes in human population and land-use change through time, and can be used to complement archaeological datasets to link human populations with palaeoenvironmental change.

  PublisherDOI

• Using faecal stanols from a tropical lake core to reconstruct human population dynamics in the southwestern Maya Lowlands

  AGU Fall Meeting Abstracts · 2018-12-01

  articleSenior author
  Publisher

• A long-term decrease in the persistence of soil carbon caused by ancient Maya land use

  Nature Geoscience · 2018-08-16 · 67 citations

  articleSenior author
  PublisherDOI

• Issues Reconstructing the Ancient Population of El Mirador, Guatemala

  The 82nd Annual Meeting of the Society for American Archaeology · 2018-01-01

  articleSenior author
  Publisher

• INTEGRATED STRATIGRAPHY OF THE LOWER AND MIDDLE FERNIE FORMATION IN ALBERTA AND BRITISH COLUMBIA, WESTERN CANADA

  Durham Research Online (Durham University) · 2015-08-28 · 24 citations

  articleOpen accessSenior author

  The lower and middle parts of the Fernie Formation in central-western Alberta and south-eastern British Columbia, ranging from Pliensbachian to ?Bathonian (Early to Middle Jurassic) in age, and consisting mainly of fossiliferous dark shales and black limestones, contain bentonitic clay horizons which have yielded radiometric ages using U-Pb analysis of zircon crystals. Here we report six new ages from the lowermost Red Deer Member (188.3 +1.5/-1 Ma); Highwood Member (ca. 173 Ma and 166.6 ± 0.2 Ma); and Grey Beds (167.0 ± 0.2 Ma, 165.6 ± 0.3 Ma, and 165.4 ± 0.3 Ma). Some of these bentonites are associated with ammonites and coccoliths which provide biostratigraphic constraints. Strontium and carbon and oxygen isotopes measured from belemnite rostra have been compared in two sections and the resulting curves are compared with those from western Europe.

  PublisherDOI

• Non-mounded Architecture, Invisible Housemounds, and the Problem of Settlement Identification and Demographics in the Mirador Basin

  The 80th Annual Meeting of the Society for American Archaeology · 2015-01-01

  article1st authorCorresponding
  Publisher

Frequent coauthors

• Peter Douglas

  McGill University

  5 shared

• Benjamin Keenan

  Université de Montréal

  4 shared

• Andy Breckenridge

  4 shared

• Carlos Morales-Aguilar

  2 shared

• Andrew Breckenridge

  2 shared

• Richard Hansen

  Idaho State University

  2 shared

• Timothy I. Eglinton

  1 shared

• Richard R. Paine

  1 shared

Education

• Ph.D., Entomology

  The Ohio State University

  2000

• M.S., Entomology

  The Ohio State University

  1996

• B.S., Entomology

  The Ohio State University

  1994