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New research gives insight into African megafauna declines

Humans aren’t the only factor nudging them toward extinction.

(CN) — Africa is known for its megafauna. Its massive, iconic creatures, such as elephants, rhinos and giraffes, have fascinated scientists for decades. African elephant populations have declined by 98% since the 1500s, leading many researchers to believe that humans pushed megafauna to extinction and endangerment. 

However, new research published in Science on Thursday takes a more extended, deeper look at African megafauna losses over the last 10 million years. Researchers Faysal Bibi at Museum für Naturkunde, Berlin, Germany, and Juan L. Cantalapiedra of the University of Alcalá, Madrid, Spain, combed through thousands of fossilized teeth to put megafauna abundance into perspective. 

Large African mammals in the study qualify at weighing approximately 15 kilograms. Bibi and Cantalapiedra found that animals weighing 45 kilograms or more tend to follow a known pattern: large species have lower populations than smaller species or the “rule of metabolic scaling.” 

The sweet spot between 15 kilograms and 45 kilograms is where the fossil record begins to deviate. About 4 million years ago, larger mammals, such as elephants weighing over 10,000 tons, had a higher population than smaller creatures inhabiting the same space. Since then, megafauna numbers have slowly but steadily declined. This shift also caused the animals to shrink in size. 

There is no doubt that humans have played a significant role in the nosedive of megafauna numbers. Large extinctions began around the same time that humans spanned across the Earth. Even so, those losses started around 100,000 years ago — a short blip in relativity to the steady 4 million year-long downswing.

This finding has Bibi and Cantalapiedra looking at the environmental factors that squeezed populations.

Over time, tropical grasslands spread, temperatures decreased and plant productivity dropped. The researchers compared the fossil tooth shapes with plant production, which declined by two-thirds globally about 5 million years ago. As plant production dropped, so did nourishment resources at every food chain level. 

Bibi and Cantalapiedra believe the research can help better predict biodiversity loss as environments change, inform conversation efforts and further research on ecosystem restructuring.

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Categories / Environment, Science

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