Around 66 million years ago, a six mile-wide (10km) asteroid smashed into the Earth off Mexico's Yucatan peninsular.

The impact wiped out three quarters of all plant and animal species - including the dinosaurs - triggering mega-tsunami, wildfires, global earthquakes.

But even Armageddon can have a silver lining, according to a new discovery which claims the event proved a turning point for the plants that now dominate vegetation on Earth.

After the impact, fast-growing seasonal species of plants began to take over from evergreens. This is according to a study of 1,000 fossilised plant leaves in North Dakota by the University of Arizona

After the impact, fast-growing seasonal species of plants rapidly began to take over from evergreens.

'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,' said lead scientist Dr Benjamin Blonder, from the University of Arizona.

'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.

Analysis of the leaf samples revealed the switch from evergreens to deciduous plants after the meteor struck

All the fossils were collected from a rock formation known as Hell Creek that marks the site of an ancient flood plain in the south of North Dakota

Dr Blonder's study provides evidence of a dramatic shift from slow-growing plants to fast-growing species.

He said it potentially tells scientists why modern forests are generally made up of seasonal plants and not evergreen.

WHERE DINOSAURS WIPED OUT BY A 'NUCLEAR WINTER'? A devastating 'impact winter', brought on by an asteroid strike 66 million years ago, is being blamed for wiping out the dinosaurs. Researchers have discovered the first physical evidence that global temperatures suddenly plummeted following the impact off Mexico's Yucatan Peninsula. Its effects would have been identical to those seen in the aftermath of a large-scale nuclear war, including the chilling effect of dust blotting out of the sun. According to the research, the 'Chicxulub' impact is likely to have brought about this 'nuclear winter' by lowering global sea surface temperatures by as much as 7°C (45°F) at a conservative estimate. For creatures evolved to live in a lush, warm, green world, the result would have been catastrophic. The 'winter' is thought to have lasted no more than two to three decades, but that was long enough to wipe out the dinosaurs, flying and swimming reptiles, and many other forms of life. Only the most adaptable survived, leading to the reign of the birds and mammals that continues to this day. Advertisement

Deciduous plants, which grow fast and lose their leaves at some point during the year, were better able to survive the changing conditions of an impact winter, the researchers believe.

Evergreen plants, such as holly, tend to have leaves that are costly to construct but robust and long-lasting. Leaves of deciduous plants are short lived and more cheaply built, but easier to replace.

'There is a spectrum between fast and slow-growing species,' said Dr Blonder. 'There is the 'live fast, die young' strategy and there is the "slow but steady" strategy.'

The discovery, reported in the online journal Public Library of Science Biology, followed a study of around 1,000 fossilised plant leaves dating back to a 2.2 million-year period spanning the impact event.

All the fossils were collected from a rock formation known as Hell Creek that marks the site of an ancient flood plain in the south of North Dakota.

Analysis of the leaf samples revealed the switch from evergreens to deciduous plants after the meteor struck.

'We measured the mass of a given leaf in relation to its area, which tells us whether the leaf was a chunky, expensive one to make for the plant, or whether it was a more flimsy, cheap one,' said Dr Blonder. 'In other words, how much carbon the plant had invested in the leaf.'

The scientists also measured the density of the leaves' vein networks, which gave a clue to their transpiration rate - the speed at which they drew water.

'[The study] tells us that the extinction was not random, and the way in which a plant acquires resources predicts how it can respond to a major disturbance,' said Dr Blonder.