Nothing. I hope the Earth doesn't hold it against me.
Seriously though, Earth Day is stupid. Either work for a cleaner, healthier environment or don't. Taking one day out of the year to recognize being kinder and gentler to our planet basically labels the 364 other days as less important. Plant trees whenever you want, recycle when you want, save energy when you can. Those goals should be prevalent every day, not just one.
Also relating to the subject, pollution won't destroy the planet, and eco-nazis who've successfully led 1 out of 3 children to believe the Earth won't be around when they grow up should be beaten with a stupid stick. Our ecosystem isn't immortal, but it's also not weak. The planet has survived meteors, ice ages, ages with no icecaps at all, and other things that the greenest of green thumbs think would be absolutely catastrophic today. It wouldn't be nice, it wouldn't be fun, and many animals and people would undoubtedly be pressed so hard that mass migration, adaptation or even death would result, but the planet would go on.
So my motto, do what's best for humanity and care for the world as best we can, while being realistic.