African grasslands expanded 5 million year earlier than previously thought, molecular fossils suggest
The iconic grassland savannas of Africa are geographically extensive and important for both local fauna and the global climate. But where did they come from, and how will they change in the future? Ongoing warming, rising CO2 levels and shifting rainfall patterns are likely to profoundly change these ecosystems. These effects are difficult to predict because they can alter ecosystems in competing…
New research published in the Proceedings of the National Academy of Sciences reveals that the iconic African grasslands known as savannas formed approximately 5 million years earlier than previously believed. Utilizing molecular fossils found in marine sediments, scientists have gained insight into the history of northwest African ecosystems over the past 24 million years.
These molecular fossils, which are carried by ocean currents from the continent, were extracted from drill cores obtained through the International Ocean Discovery Program. The study led by Anna Schartman during her Ph.D. at UC Santa Cruz, in collaboration with her adviser Pratigya Polissar and Professor Caroline Strömberg, determined that the first open grassland ecosystems appeared around 15 million years ago.
This discovery contradicts earlier estimates and provides a more accurate timeline of the evolution of African grasslands. The early grasslands differed from modern savannas and underwent significant changes over millions of years due to factors such as global cooling, aridification, wildfire, and herbivory. Understanding the emergence and transformation of these ecosystems is crucial as they played a pivotal role in shaping African biodiversity, including the evolution of our human ancestors.
The findings highlight the complex interplay between climate, wildfire, and herbivores that continues to influence these ecosystems today.
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