How flowers completely changed Earth's weather 100 million years ago

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Wondering why the weather is so strange lately? Why it's raining all the time in certain parts of the globe, but really dry in others? It's all because of flowers.


In geologic time, flowers are a relatively new player on the planetary scene - so by "lately," I mean "in the last 100,000 or so millennia." Flowers evolved about 130 million years ago, millions of years after forests and giant animals had come to dominate the planet. Unlike the plants and trees that came before them, flowering plants (known as angiosperms) are rain factories. In the hundreds of thousands of years after they evolved, flowers started to make the planet a lot wetter. About 10% of the moisture in our atmosphere comes from these plants, which suck water out of the ground and then release it into the atmosphere when the water evaporates from their leaves. This process is called "transpiration" - it's sort of the flower version of sweating.

So what would our planet be like without flowering plants? A group of researchers decided to find out. According to ScienceNOW:

To simulate a world without angiosperms, the researchers rejiggered climate models, cutting transpiration by 75%-the approximate amount contributed by these plants. The effects were complex, with some areas drying and some even becoming wetter. Eastern North America, for example, received 30% to 50% less precipitation. But the biggest impact occurred in tropical areas of South America . . . Without angiosperms, average annual rainfall in the area declined by 300 millimeters. In the eastern Amazon basin, the length of the wet season decreased by nearly 3 months. The extent of the wettest rainforests, which receive more than 100 millimeters of rain per month, shrank by 80%. The effects weren't as severe in other tropical areas, such as in Africa, which already has lots of dry tropical forests.

A drier world would have been bad for other species, too. As a rule, less precipitation translates into fewer species of animals and plants-that's why deserts are biologically deprived. So angiosperms' transpiration capacity might have been important not just ecologically but also evolutionarily, spurring the origin of more tropical species, including other angiosperms. "They modify their environment in ways that bolster their own diversity," [geophysicist and study co-author Kevin] Boyce says.

In other words, kill the flowers and you radically alter our planet's climate. That doesn't mean you'd destroy all life: The planet was teeming with many different creatures before flowers evolved - trees like ginkos and pines filled the forests, and before that the wet regions of the Earth were clogged with seaweed-like plants. But these researchers' climate model, published today in Proceedings of the Royal Society B, proves that flowers are an important anchor for our current ecosystem. Plants rule the planet.

via ScienceNOW - full paper at Proceedings of the Royal Society B

Top image by Sretco Milanovici/Shutterstock.



Well then it isn't actually flowers that changed the weather, it's flowering plants and their nifty stomata.

But FYI, pretty much all plants transpire, including gymnosperms (like pine trees) and ferns, both of which are not angiosperms. Anything with vascular tissue (i.e. not a bryophyte like moss) transpires and will affect the amount of water that is in the ground or in the air.