'it' likes the pronoun 'they'
the planet is singular, its the earth, not the earths. so it is appropriate. it the planet will just shake us off with mass earth quakes and volcanos, maybe a shifting of the poles, or maybe an asteroid will do the job. its happened before, look into it, lol. we cause too much bother and kablam! bibi puny humans, time for another ice age and a reset, you human fucks don't deserve to be custodians any more.