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Assessing 500,000-Year-Long Variations in Climate and Vegetation

Earth scientists from Heidelberg University investigated natural climate and vegetation variations over the last 500,000 years to forecast the effects of human-induced climate change on Mediterranean ecosystems. Their main focus was the impact of these changes on the forests of the Mediterranean region.

Assessing 500,000-Year-Long Variations in Climate and Vegetation
Approx. 400,000 years old Pollen grains from Tenaghi Philippon under the microscope. Due to their good preservability, they also remain intact in drill cores, making it possible to reconstruct vegetation and climate changes in the geological past. Image Credit: © Ulrich Kotthoff

To that end, investigators headed by Dr. Andreas Koutsodendris examined fossil pollen preserved in a sediment core from Greece. Their findings indicate that, under long-term drought conditions, as predicted by the most recent climate models, desertification of the Mediterranean region's forests is likely in the near future.

Mediterranean forests are not only biodiversity hotspots, but they also provide essential ecosystem services. They prevent soil erosion, control regional climate and hydrological conditions, and provide food and timber.

Because they are exceptionally sensitive to climate change, concern for their survival is growing in light of anthropogenic CO2 emissions and associated global warming.

Dr. Andreas Koutsodendris, Institute of Earth Sciences, Heidelberg University

Dr. Andreas Koutsodendris is a member of Prof. Dr. Jörg Pross’s research group at Heidelberg University’s Institute of Earth Sciences, which studies the Earth’s environmental and ecosystem dynamics.

The Heidelberg investigators, in collaboration with colleagues from Germany, France, Greece, and the United Kingdom, took drill cores from Tenaghi Philippon, a terrestrial climate archive in the northeast of Greece that provides a complete record of the past 500,000 years and contains fossil pollen grains, to trace how Mediterranean forests reacted to climate changes in the past.

The pollen grain data on vegetation development during this time period was connected with geochemical data on precipitation changes. The findings of the research directed by Dr Koutsodendris reveal that in the past when precise precipitation thresholds were reached, Mediterranean forests converted into steppes within a few decades.

Using ecological models, the researchers investigated potential causes of changes in precipitation patterns. Their findings indicate that changes in atmospheric CO2 content have an impact on the amount of precipitation in the Mediterranean region.

In the past, a decrease in rainfall of 40 to 45 percent was sufficient to set off a sudden shift from forest to steppe biomes under natural conditions.

Dr. Andreas Koutsodendris, Institute of Earth Sciences, Heidelberg University

According to the Heidelberg Earth scientist, these findings show that such a shift could occur in the Mediterranean region's forests in the near future if nothing is done to protect them.

The German Research Foundation, the State of Hessen, as part of its state initiative for promoting scientific and economic excellence, and the Wilhelm Schuler Foundation provided funding for the research.

Journal Reference:

Koutsodendris, A., et al. (2023). Atmospheric CO2 forcing on Mediterranean biomes during the past 500 kyrs. Nature Communications.


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