The meteorite that spelled doom for dinosaurs 66 million years ago restructured our forests - decimating the slow-growing evergreen species, allowing them to be replaced by deciduous trees, a new study has found.
Some 66 million years ago, a 10-km diameter chunk of rock hit the Yukatan peninsula near the site of the small town of Chicxulub with the force of 100 teratons of TNT.
It left a crater more than 150 km across, and the resulting megatsunami, wildfires, global earthquakes and volcanism are widely accepted to have wiped out the dinosaurs and made way for the rise of the mammals.
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The study led by researchers from the University of Arizona shows that the impact that spelled doom for the dinosaurs also decimated the evergreen flowering plants to a much greater extent than their deciduous peers.
The researchers hypothesise that the properties of deciduous plants made them better able to respond rapidly to chaotically varying post-apocalyptic climate conditions.
Applying biomechanical formulae to a treasure trove of thousands of fossilised leaves of angiosperms - flowering plants excluding conifers - the team was able to reconstruct the ecology of a diverse plant community thriving during a 2.2 million-year period spanning the cataclysmic impact event, believed to have wiped out more than half of plant species living at the time.
The fossilised leaf samples span the last 14,00,000 years of the Cretaceous and the first 800,000 of the Paleogene.
The researchers found evidence that after the impact, fast-growing, deciduous angiosperms had replaced their slow-growing, evergreen peers to a large extent.
Living examples of evergreen angiosperms, such as holly and ivy, tend to prefer shade, don't grow very fast and sport dark-coloured leaves.
"When you look at forests around the world today, you don't see many forests dominated by evergreen flowering plants," said the study's lead author, Benjamin Blonder.
"Instead, they are dominated by deciduous species, plants that lose their leaves at some point during the year," said Blonder.
Blonder and his colleagues studied a total of about 1,000 fossilised plant leaves collected from a location in southern North Dakota, embedded in rock layers known as the Hell Creek Formation, which at the end of the Cretaceous was a lowland floodplain crisscrossed by river channels.
"If you think about a mass extinction caused by catastrophic event such as a meteorite impacting Earth, you might imagine all species are equally likely to die," Blonder said.
"Survival of the fittest doesn't apply - the impact is like a reset button. The alternative hypothesis, however, is that some species had properties that enabled them to survive.
"Our study provides evidence of a dramatic shift from slow-growing plants to fast-growing species," he said.
The study was published in the journal PLOS Biology.
