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Mass Extinctions: Plants Are Resilient, Animals Are Not

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When the Earth has experienced episodes of mass extinctions plants have fared much better than animals, proving more resilient, researchers have found.

In the five such known extinction events in Earth's long history, plants have shown a greater ability to survive than the animals that share our planet, scientists at the University of Gothenburg in Sweden say.

Plants, which have served a crucial role in almost every terrestrial environment on the surface of the Earth, have managed to survive even major extinction events that had severe effects on every terrestrial ecosystem and the planet's overall biodiversity, they've discovered.

Analysis of some 20,000 plant fossils to gauge the effects those events have had on plant diversity showed mass extinctions have had very different impacts among plant groups, the researchers say.

Periods when plant biodiversity declined -- when older plant species died faster than new plant species were being formed -- were never sustained for long, a good indicator of their ability to survive rough periods and then recover afterward, they say.

"In the plant kingdom, mass extinction events can be seen as opportunities for turnover leading to renewed biodiversity," lead study author Daniele Silvestro says.

One of the Earth's great mass extinctions 66 million years ago, when a giant asteroid impacted the planet off Mexico's Yucatan Peninsula and killed off the dinosaurs, had surprisingly little effect on plant diversity, the researchers have determined.

While some plant groups, such as the gymnosperms -- which includes spruce, pines and firs -- did lose a significant amount of their diversity following the impact, flowering plants (angiosperms) did not and in fact underwent a rapid increase in their diversity immediately after the event.

It is one reason flowering plants dominate the global diversity today over all the other plant groups, the researchers say.

"Mass extinctions are often thought as a bad thing, but they have been crucial in changing the world into how we know it today," says researcher Alesandre Antonelli.

Without the asteroid impact, dinosaurs could still be around, mammals might still be small, timid creatures confined to caves, and humans -- well, we might never have evolved, the researchers suggest.

The findings have relevance for today's world, they say.

"By studying such extreme events we are trying to learn which groups of organisms and features are more sensitive to changes, so that we can apply this knowledge to protect biodiversity in the face of on-going climate change and human deterioration of natural ecosystems," Antonelli says.

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