MELBOURNE, Oct. 16 (Xinhua) -- Extreme global warmth drove both mass extinctions and explosions in plant diversity during two periods over the past 140 million years, offering new insights into how flowering plants became dominant on Earth, a new study has found.
The study examined fossilized pollen and spores to show that the mid-Cretaceous and early Cenozoic periods of extreme global warmth were central to plant evolution, both for flowering plants and the other main types on Earth, according to a statement released Thursday by Australia's University of Tasmania (UTAS).
Researchers said that land plants sustain almost all terrestrial animals, fungi and bacteria, while flowering plants are the most productive and diverse group, with about 400,000 species worldwide.
The team examined more than 60,000 fossil occurrences and applied methods that overcome the major biases in the fossil record, generating revised estimates of fossil pollen and spore diversity over the past 130 million years, according to the study published in Nature Plants.
Both plant extinctions and the emergence of new but evolutionarily related plant groups occurred mostly during the two periods of extreme global warmth, said the study's co-author, UTAS Professor Greg Jordan.
Each interval lasted several million years, with warming simultaneously destroying and promoting plant diversity "over million-year timescales," Jordan said. In contrast, cooler periods were marked by little change in plant diversity.
However, the researchers warned that human-driven warming is likely to cause plant extinctions much faster than past extreme warming events. ■
