6 June 2023

Mediterranean forests face desertification risk


In the past, forests around the Mediterranean Sea partly turned into steppes within a few decades as precipitation rates changed. Today, a German research explains, this scenario could happen again

by Matteo Cavallito


Affected by prolonged drought phenomena, forests in the Mediterranean area are likely to face desertification in the near future. An event described as “likely” according to the latest climate models. This was suggested by a research carried out by a group of earth scientists from the University of Heidelberg, Germany. Researchers studied natural fluctuations in climate and vegetation over the past 500,000 years.

The study authors, led by researcher Andreas Koutsodendris, analyzed fossil pollen preserved in a sediment sample from Greece. In this way they tried to predict the consequences of human-caused climate change on ecosystems. The results of the investigation have been published in the journal Nature Communications.

The study

Scientists developed their analysis by reconstructing the reaction of Mediterranean forests to climate change in the past. To achieve this goal, the German researchers, in collaboration with colleagues from France, Greece, and the United Kingdom, took soil samples from the Tenaghi Philippon area using the coring method.

This site, located in northeastern Greece, represents a genuine terrestrial climate archive in which fossil pollen grains are preserved intact in the soil.

“The data on vegetation development in this period gained from the pollen grains was correlated with geochemical data on contemporaneous fluctuations in precipitation,” says a statement from the University of Heidelberg. “The results of the team led by Dr Koutsodendris show that, in the past, the Mediterranean forests transformed into steppes within a few decades as soon as specific precipitation thresholds were crossed.”

The transformation can happen again

Using ecological models, scientists reconstructed past transformations. “Our analysis documents two stable vegetation regimes across the wide range of CO2 and moisture levels realized during the past four glacial-interglacial cycles,” the study states. “Our approach highlights that a CO2-driven moisture decrease in the near future may bear an impending risk for abrupt vegetation regime shifts prompting forest loss in the Mediterranean region.”

The premise is still applicable today. With obvious consequences. “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,” says Koutsodendris. As a result, he adds, such a change could occur in the near future if action is not taken to protect forests.

Mediterranean forests provide essential ecosystem services

Concern about the future of Mediterranean forests, however, is also linked to the loss of the ecosystem services associated with them. In addition to conserving extensive biodiversity, in fact, these environments protect against soil erosion, regulate regional climate and hydrological conditions, and provide food and timber.

“In light of yet unabated anthropogenic CO2 release, there is increasing concern on the resilience of these forest biomes to the recurring droughts as they are projected for the Mediterranean region in the next 70 years,” the research explains.

Also monitoring desertification risk are periodic computations by the Joint Research Center’s European Drought Observatory (EDO), based on the CDI drought index. This is obtained by combining a comparison of current and past years’ rainfall (for the same period), abnormal soil moisture content, and an assessment of the impact drought has on local vegetation. The Observatory’s latest data show that 21.3 percent of the EU territory is in an “Alert” condition and 5.6 percent is in a “Warning” situation.