A research team from the Senckenberg Biodiversity and Climate Research Center in Frankfurt, the German Center for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig and Friedrich Schiller University Jena has investigated the impact of climate change on mammalian diversity in Central Asia during the Paleogene. Their study, now published in the scientific journal “Nature Communications,” shows that between 66 and 23 million years ago, a regional arid phase – in addition to global temperature shifts – played a decisive role in shaping the evolution of mammalian communities.
The Paleogene period, approximately 66 to 23 million years ago, was a pivotal era in mammalian evolution. After the dinosaurs became extinct about 66 million years ago, mammals rapidly established themselves as the dominant group of terrestrial vertebrates. How did these animal communities change over this long period, and what role did climate change play in this process? An interdisciplinary team led by Dr. Gemma Louise Benevento, a researcher at the German Center for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig and the Friedrich Schiller University Jena and formerly with the Senckenberg Biodiversity and Climate Research Center in Frankfurt, investigated these questions with a focus on Central Asia.
“Based on fossil finds in Mongolia and China, we have reconstructed the taxonomic diversity and composition of mammalian communities, as well as the evolution of the animals’ body mass over time,” explains Benevento. “In the process, we identified three phases marked by significant changes in our study area in Central Asia during the Paleogene. These shifts in the evolution of mammalian communities coincide with major climatic events during this period. First, with the rapid warming phase of the Paleocene-Eocene Thermal Maximum about 56 million years ago; second, with the cooling at the transition from the Eocene to the Oligocene about 33.9 million years ago. As a third climatic change – occurring between these two events – we were also able to identify an additional regional aridification phase in Central Eastern Asia during the Middle Eocene.”
During the Paleocene-Eocene Thermal Maximum about 56 million years ago, the Earth’s temperature increased by about five to ten degrees Celsius over a relatively short period of about 100,000 years. This “greenhouse world” then began to change about 33.9 million years ago, when a phase of gradual cooling and aridification ushered in a long-term transition to a cooler “icehouse world” with ice caps covering the poles.
“In addition to these global climate events, several recently published geological and ecological analyses have provided evidence of a period of aridification in Central Eastern Asia as early as the Middle Eocene, about 40 million years ago,” explains Benevento. “These studies are based on indicators such as weathering intensity, which decreases in arid regions, and pollen, which serves as an indicator of past environmental conditions. For this period, an increase in pollen species typical of desert landscapes was observed. Using climate model simulations, we have now been able to independently confirm this regional arid phase. Our climate models also indicate that the environment in this region became drier about six million years earlier than previously assumed.”
According to the study, global warming resulting from the Paleocene-Eocene Thermal Maximum, which was accompanied by the greening of inland deserts, fostered a high diversity of mammals, which tripled during this period. In contrast, the subsequent aridification and cooling are believed to have led to a decline in species diversity, a decrease in body size, and, overall, a significant transformation of animal communities.
“The fact that the arid phase began earlier in Central Asia than in other parts of the world is likely linked to changes in air currents caused by the retreat of the Paratethys Sea – a vast, now-vanished inland sea in Eurasia – and the uplift of the Tibetan Plateau,” says Benevento. “It is particularly noteworthy that this regional aridification phase apparently impacted mammalian communities to a similar degree as the ‘major’ global climate events. This also allows us to draw valuable conclusions regarding today’s climate change and increasing global warming. To identify the most significant threats to present-day biodiversity, it is essential to also consider regional and local changes – such as water availability, atmospheric moisture transport, or habitat shifts. This is the only way we can reliably assess how today’s mammal communities will respond to future changes in climate and the environment.”
