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Early Pleistocene ecosystem turnover in South Siberia linked to abrupt regional cooling

Nature Geoscience (2026)Cite this article

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Abstract

Earth system feedbacks can amplify greenhouse gas forcing but are difficult to quantify, particularly on land where long palaeoclimate records are scarce. Here we reconstructed warm-season temperatures and vegetation at Lake Baikal, Russia, over the past 8.6 million years. We document gradual late Neogene cooling that was punctuated by an abrupt transition approximately 2.7 million years ago to severe cold temperatures during glacial periods. Forests were replaced by open steppe–tundra ecosystems and permafrost probably extended into South Siberia during these Early Pleistocene cold intervals. Compiled palaeobotanical data suggest this ecosystem turnover occurred throughout the Arctic and subarctic, although the timescale of these changes is less understood. Reconstructed Early Pleistocene glacial temperatures and vegetation resemble Late Pleistocene glacial periods at Lake Baikal, despite much warmer mean global temperatures in the Early Pleistocene. These geologic observations support the view that regional climate can respond nonlinearly to global forcing. We hypothesize that both vegetation albedo and permafrost carbon storage may have played a key role in amplifying glacial–interglacial climate cycles through the last 2.7 million years alongside ocean and ice sheet feedbacks.

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Fig. 1: Late Neogene ecosystem and temperature change at Lake Baikal.
Fig. 2: Compiled vegetation data.
Fig. 3: Lake Baikal warm-season temperature anomalies as a function of global mean surface temperature change.
Fig. 4: Continuous permafrost during glacial periods since 2.7 Ma.

Data availability

All data are available in the Supplementary Information, via figshare at https://doi.org/10.6084/m9.figshare.28498862 (ref. 92) and via PANGAEA at https://doi.org/10.1594/PANGAEA.986603 (ref. 93). Source data are provided with this paper.

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Acknowledgements

This work is dedicated to the memory of Mikhail I. Kuzmin, who, together with Takayoshi Kawai and Douglas F. Williams, led the Baikal Drilling Project (BDP) in 1992–2002. In 2019 he welcomed J.B.N. in Irkutsk and helped initiate this research. We thank the BDP members and the University of Rhode Island Marine Geological Samples Laboratory for access to drill core materials. J.B.N. thanks M. R. Alexandre for assistance analysing GDGTs at Brown University. J.B.N. thanks M. I. Kuzmin and A. T. Korolkov for their support and encouragement. This work was supported by the National Science Foundation NNA 22-02918 (J.B.N., P.J.P.), PR 1414/1-1 Deutsche Forchungsgemeinshaft Priority Program ‘ICDP’ 1006 (AAP), Geological Society of America Continental Drilling Science Division Graduate Student Grant 13282-21 (J.B.N.) and Sigma Xi Grants in Aid of Research G20211001-101 (J.B.N.) and the ARCS Scholarship (J.B.N.).

Author information

Authors and Affiliations

  1. Ocean Sciences Department, University of California, Santa Cruz, CA, USA

    Joseph B. Novak, Emma R. Lindemuth & Pratigya J. Polissar

  2. Institute of Mineralogy, University of Cologne, Cologne, Germany

    Alexander A. Prokopenko

  3. Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany

    Pavel E. Tarasov

  4. Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI, USA

    James M. Russell

  5. Forestry and Forest Products Research Institute, Hokkaido Research Center, Sapporo, Japan

    Koji Shichi

  6. Kanazawa University, Kanazawa, Japan

    Kenji Kashiwaya

  7. Department of Geosciences, University of Akron, Akron, OH, USA

    John Peck

  8. Department of Geological Sciences, Auburn University, Auburn, AL, USA

    Richard S. Vachula

  9. School of Geography, University of Nottingham, Nottingham, UK

    George E. A. Swann

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  1. Joseph B. Novak
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  2. Alexander A. Prokopenko
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Contributions

Conceptualization: J.B.N., P.J.P., A.A.P., J.M.R., R.S.V. and G.E.A.S. Methodology: J.B.N., P.J.P., A.A.P., P.E.T. and J.M.R. Investigation: J.B.N., E.R.L., A.A.P., P.E.T., K.S., K.K. and J.P. Visualization: J.B.N. Funding acquisition: J.B.N., P.J.P. and A.A.P. Project administration: P.J.P. Supervision: P.J.P. Writing–original draft: J.B.N. Writing–review and editing: J.B.N., P.J.P., A.A.P., P.E.T., J.M.R., K.S., K.K., J.P., R.S.V. and G.E.A.S.

Corresponding authors

Correspondence to Joseph B. Novak or Pratigya J. Polissar.

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The authors declare no competing interests.

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Nature Geoscience thanks Sarah Feakins and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: James Super, in collaboration with the Nature Geoscience team.

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Extended data

Extended Data Fig. 1 Climate and environmental changes at Lake Baikal 2.7 Ma.

(a) Warm season temperatures reconstructed from brGDGTs. Gray shading is the 68% confidence interval, red points are the mean. (b) Average chain length of n-alkanes (ACL, vegetation proxy). (c) Warm–temperate broad-leaved evergreen plant functional-type score. (d) Median grain size of bulk sediments26. φ values of ~8 correspond to glacial clays, φ values of 6–7 correspond to the typical size of diatom frustules in Late Pliocene and Early Pleistocene Lake Baikal sediments reported by ref. 28.

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Supplementary information

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All supporting data associated with this work.

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Source Data Fig. 1

The Lake Baikal palaeotemperature record, pollen plant functional-type scores, reconstructed dominant biomes and the global mean surface temperature change stacks.

Source Data Fig. 2

Compiled palaeobotanical datasets from Northern Hemisphere boreal regions.

Source Data Fig. 3

Global mean surface temperature stack anomaly data and Lake Baikal temperature anomalies.

Source Data Fig. 4

The Lake Baikal palaeotemperature and n-alkane average chain length records, with samples from the last ~500 ka classified as belonging to periods with or without local permafrost.

Source Data Extended Data Fig. 1

Lake Baikal palaeotemperature record, n-alkane average chain length record, warm–temperate evergreen plant functional-type scores and median grain size records from 2.0 to 3.5 Ma.

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Novak, J.B., Prokopenko, A.A., Tarasov, P.E. et al. Early Pleistocene ecosystem turnover in South Siberia linked to abrupt regional cooling. Nat. Geosci. (2026). https://doi.org/10.1038/s41561-025-01914-x

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