55 million years ago, the world was literally a jungle. With such high temperatures, rainfall and humidity, life could proliferate. But 49 million years ago, something drastic happened: The Azolla Event, where ice was forming at the poles. The culprit? A kind of plant called Azolla. Within 800,000 years, photosynthesis and carbon sequestration from those plants reduced the atmospheric quantity of carbon dioxide from more than 3000 parts per million to 650.

[figure from Atmospheric carbon dioxide concentrations over the past 60 million years]

But the real question here is--did the cooling caused by the Azolla Event create a major extinction event of plant and animal species?

The azolla event lasted for nearly 1 million years I think most plants and animals can adapt while the event was going on.