- An asteroid impact near Mexico 66 million years ago triggered an ecological catastrophe that claimed nearly half of all plant species and took Amazon forests more than 6 million years to recover from.
- Colombian researchers analyzed fossilized pollen and leaves and found plant diversity declined by 45% after the impact; when plant diversity finally recovered, open forests of ferns and conifers had been replaced by dense, closed-canopy forests dominated by flowering plants.
- The researchers suggested three interlinked explanations for the sudden transition: the extinction of large-bodied dinosaurs at the end of the Cretaceous reduced forest disturbance; dust from the impact acted as a fertilizer; conifers were more likely to go extinct.
- In the time periods studied, Earth’s climate was warmer and CO2 levels were higher, showing that climate alone is not enough to trigger a forest-to-savanna transition, with the pace of warming and deforestation the crucial puzzle pieces that determine whether today’s forests can survive.
The mass extinction that followed claimed nearly half of all tropical plant species and shifted Amazonian ecosystems from open-canopy forests dominated by ferns to the dense closed canopy rainforests we know today, the researchers report.
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