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Range-wide Tsuga tree decline driven by abrupt climate changes in mid-Holocene America
1Department of Geology and Geophysics, University of Wyoming, Laramie, 82071, WY, USA.
The New Phytologist
|August 13, 2026
Summary
Eastern hemlock (Tsuga canadensis) populations collapsed across North America due to climate shifts linked to the Atlantic Meridional Overturning Circulation. Regional climate changes, including droughts and altered temperature/precipitation patterns, compressed the species' climate niche.
Area of Science:
- Paleoecology
- Climate Science
- Botany
Background:
- Eastern hemlock (Tsuga canadensis) experienced a widespread, abrupt decline during the Holocene, puzzling paleoecologists.
- This ancient forest collapse highlights potential risks of ecological tipping points and climate variability impacting species distributions today.
Purpose of the Study:
- To investigate the causes of the Holocene range-wide decline of eastern hemlock.
- To test hypotheses linking the decline to climatic shifts and ecological factors.
Main Methods:
- Analysis of fossil pollen and paleoclimatic records across the eastern hemlock range.
- Application of synchrony tests, regression, and gradient analyses to identify climate-decline relationships.
Main Results:
- The eastern hemlock decline was time-transgressive and directly linked to climatic shifts driven by the Atlantic Meridional Overturning Circulation.
- Regional climate variations, including eastern droughts and altered snowbelt/highland conditions, compressed the hemlock climate niche, eliminating refugia.
- The decline demonstrated a strong sensitivity to interacting temperature and precipitation changes.
Conclusions:
- The Holocene collapse of eastern hemlock was primarily driven by climate change, not insect or pathogen outbreaks.
- Understanding past climate-driven range contractions is crucial for predicting future species responses to environmental change.
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