This is not a fact. I think this is common knowledge, but it's important to the rainforest.
When one species dies out, it affects a lot of other species as well. If all plants died out, no life would exist, and if the sun died (which won't happen for billions of years) no life would exist because plants would die, and because it would be freezing cold. (That was random; the sun won't die anytime soon.) My point is, if enough animals, plants, fungi, and even bacteria died out, humans would die out as well, and we should care more about life on Earth other than us.