If Earth Had Rings
First off, they would be really pretty to look at. They would also dominate the sky in both night and day at exactly the same place as they would never rise nor set. And at night you would see the Earth’s shadow swing across the rings, like in the 4th photo here.
However, life would be very different on Earth if this were the case. Nocturnal animals would have a hard time being nocturnal, as the light reflecting from the rings would illuminate the night.
Because we are closer to the Sun than Saturn is, the rings would be more rocky than ice, making them less bright but still pretty bright. In fact, you would see far less stars at night (living anywhere other than the equator or the arctic circle) because of the light pollution and not to mention ruin most meteor showers because of that.
During the day the rings would block sunlight in certain regions of the planet creating wild weather cycles and effecting plant life as well. So basically, they would be definitely pretty to look at but they would also make a whole lot of things screwy.
Illustrations by Ron Miller // io9
— Click the photos for captions
On the other hand, if it had had rings all along, then plants and animals would have evolved to suit that environment. The really nocturnal animals, who couldn’t bear the ringlight, probably wouldn’t be the ones passing their genes along, so the ones that did would be adapted to these situations.
Of course, if Earth SUDDENLY got rings, we’d be pretty screwed up… but things would suit the environment if they had been there all along.
I WANT RINGS ON MY PLANET. Those are so pretty! (And this reminds me that I need more sci-fi in my life with ring planets …) Light pollution is a good point though; I hadn’t ever thought of that being an issue, but obviously it would be.
However, speaking as someone who lives in a part of the world with 24-hour daylight from May to July … it’s not actually that bad, and I think nature would adapt just fine. Some plants and animals would probably have a harder go of it, but there aren’t very many animals that are so truly nocturnal that they can’t handle light at all (we have bats and owls here in Alaska, for example). It does throw plants’ life cycles off a bit, but not to the extent that you literally cannot grow plants from places with a more stable day-night cycle in Alaska.
Nature is adaptable! That’s how it works.