80 million years old rainforest

Plant fossils from Egypt shed light on the evolutionary history of rainforests

Fossil plants such as the arum Afrocasia are indicative of tropical rainforests
Fossil plants such as the arum Afrocasia are indicative of tropical rainforests in the Late Cretaceous. Image source: Clément Coiffard / Freie Universität Berlin
An international team of researchers led by first author Dr. Clément Coiffard of Freie Universität Berlin and Senckenberg scientist Dieter Uhl has taken a close look at the evolutionary history of tropical rainforests. In their study, published today in the journal "Biogeosciences," the researchers conclude on the basis of fossil flora from Egypt that there were already extensive tropical forest areas in northeastern Africa comparable to today’s rainforests in the late Cretaceous period, about 80 million years ago. (Study: https://bg.copernicus.org/articles/20/1145/2023/ )

Green and moist all year round, inhabited by colorful birds, elegant predators, long lianas and tree giants: Today’s rainforests are among the most species-rich and fascinating habitats on our planet. The time in the earth’s history at which these ’hotspots of biodiversity’ developed is disputed in science. On the one hand, studies based on modern plants suggest that tropical rainforests existed 100 million years ago, but on the other hand, no corresponding fossil evidence older than about 70 million years has been identified so far," explains lead author of the study Dr. Clément Coiffard from Freie Universität Berlin.

The Egyptian-German team wanted to resolve this inconsistency in science in their current study. For this purpose, the researchers examined fossil leaves collected in the years 1984 and 1987 in the Quseir Formation of southern Egypt, which are now kept in the collections of the Museum für Naturkunde Berlin. ,,The sediments of the Quseir Formation are characterized by humid habitats with a tropical warm-humid climate. Previous work focusing on the material studied recorded 37 fossil plant species at this site - our current study of the 21,361 fossil specimens, on the other hand, led to the identification of 70 distinguishable plant types: 54 dicotyledons, 22 angiosperms, eleven monocotyledons, four ferns, and a single conifer," explains Dieter Uhl of the Senckenberg Research Institute and Natural History Museum Frankfurt, and continues: "Accordingly, we see here both a great diversity of flora and a composition of vegetation that resembles that of today’s rainforests - such as fossil evidence of the arum family, which we find recently predominantly in the tropics."

Even the isolated occurrence of fossil charcoal in the sediments - an indication of fires in the area - is not an exclusion criterion for the presence of tropical rainforests, the researchers say in their study. "We also know of fires from today’s rainforests. Moreover, during the Cretaceous period, global temperatures and, at times, the oxygen content of the atmosphere were significantly higher than today, which favors fires," said co-author Dr. Haytham El-Atfy of the University of Tübingen and Mansoura University in Egypt.

Taken together, the plant fossils studied and the sediments surrounding them fulfill all the characteristics that are also found in today’s tropical rainforests: a diverse, tropical flora, tropical climate with an annual mean temperature of 26 to 33 degrees Celsius, no distinct seasons, and predominantly humid conditions. We therefore assume that there were already extensive tropical rainforests in northeastern Africa during the peak phase of the dinosaurs, about 80 million years ago. With an area of at least 550,000 square kilometers, they were about as large as ten percent of the recent Amazon rainforest and 25 percent of the Congolese rainforest," summarizes Dr. Clément Coiffard of Freie Universität Berlin.

The Senckenberg Gesellschaft für Naturforschung is an institution of the Leibniz Association and has been researching the "System Earth" worldwide for more than 200 years - in the past, the present and with forecasts for the future. We conduct integrative "geobiodiversity research" with the aim of understanding nature with its infinite diversity in order to preserve it as a basis of life for future generations and to use it sustainably. In addition, Senckenberg communicates research results in a variety of ways, especially in the three nature museums in Frankfurt, Görlitz and Dresden. The Senckenberg Nature Museums are places of learning and wonder, and they serve as open platforms for democratic dialogue - inclusive, participatory and international. senckenberg.de.

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