Skip to content

Research at St Andrews

Climate and growing season variability impacted the intensity and distribution of Fremont maize farmers during and after the Medieval Climate Anomaly based on a statistically downscaled climate model

Research output: Contribution to journalArticlepeer-review


Marcus J Thomson, Glen M Macdonald

School/Research organisations


The rise and decline of many complex, pre-European maize-farming cultures in the American Southwest coincides with the warm, climatically quiescent Medieval Climate Anomaly (MCA, ca. 850–1350 CE) and transition to the cool, hydrologically variable Little Ice Age (LIA, ca. 1350–1850 CE). The effects of drought on early subsistence agriculture in the Southwest is well studied, but the impact of temperature stress and variability on the growth of maize crops and which areas were most resilient to such stress remain open questions. We statistically downscaled outputs from a paleo-climate model experiment (CESM1 LME) to map changes to cumulative growing degree days for maize (GDD, 30/10 °C) and precipitation over Utah between 850 and 1449 CE, and downscaled GDD changes to local Fremont Culture archaeological site occupations from radiocarbon-dated contexts mapped as spatially discrete kernel density estimates of summed probability distributions (SPDs). We then analyzed correspondences between Fremont SPDs and GDD/precipitation between 850 and 1449 CE. In general, we found (1) high Fremont occupation intensity coincident with GDD that is less volatile than the long term average, and low occupation intensity coincident with, or following, periods of volatile GDD; (2) intensified occupation of high-elevation sites during the MCA, followed by a retreat to lower elevation sites coincident with a sudden rise in annual temperature volatility and increasing drought conditions; and (3) these occupation changes occurred in spite of the greater temperatures and variability in GDD at low-elevation sites. We found evidence that increased inter-annual variability of growing seasons prior to the onset of the LIA, was likely a determinant of Fremont subsistence strategy decision making, and high-elevation site occupation. The most resilient Fremont occupations in the face of these challenges were sited where growing season lengths were least variable.


Original languageEnglish
Article number105002
Number of pages12
JournalEnvironmental Research Letters
Issue number10
Publication statusPublished - 21 Sep 2020

    Research areas

  • Fremont, Zea mays, Climate, Growing degree days, Temperature variability

Discover related content
Find related publications, people, projects and more using interactive charts.

View graph of relations

Related by journal

  1. A meta-analysis of the relationship between companies’ greenhouse gas emissions and financial performance

    Galama, J. T. & Scholtens, B., 25 Mar 2021, In: Environmental Research Letters. 16, 4, 24 p., 043006.

    Research output: Contribution to journalArticlepeer-review

  2. Carbon cycle dynamics during episodes of rapid climate change

    Meissner, K. J., Brook, E., Finkelstein, S. A. & Rae, J., 23 Mar 2021, In: Environmental Research Letters. 16, 4, 8 p., 040201.

    Research output: Contribution to journalEditorialpeer-review

  3. The distribution and amount of carbon in the largest peatland complex in Amazonia

    Draper, F., Roucoux, K. H., Lawson, I. T., Mitchard, E., Honorio Coronado, E., Lahteenoja, O., Torres Montenegro, L., Valderrama Sandoval, E., Zarate, R. & Baker, T., 15 Dec 2014, In: Environmental Research Letters. 9, 12, 124017.

    Research output: Contribution to journalArticlepeer-review

  4. Andean grasslands are as productive as tropical cloud forests

    Oliveras, I., Girardin, C., Doughty, C. E., Cahuana, N., Arenas, C. E., Oliver, V., Huasco, W. H. & Malhi, Y., Nov 2014, In: Environmental Research Letters. 9, 11, 10 p., 115011.

    Research output: Contribution to journalArticlepeer-review

ID: 270724596