I began thinking one day at work the other night , what would be the most logical thing to occur if aliens came to earth.
I hypothetized that the government would hold the earth as hostage To have something to negate with. Mostly to keep the upper hand, for even now when we think of going to other solar systems to find life, we do it for that reason to find life. So if the aliens came here they came for scientific/religious(spiritual) reasons, cause even now we have this longing this existential desire to know if we are alone or not alone in the universe.
As to why the government would use all life on this planet as black mail? Simple to keep control, they don’t want the population to know, there is a higher more powerful force then it. That is isn’t a higher power to call upon for help, that there isn’t this “destroyer” in the sky. The most valueable resource on the planet and to other intelligent life forms has to be life, unless it’s far more common then we think. Which I don’t think it is, theirs 8 planets in or solar system and one has life.
Even tho I believe the aliens view of how to interact with life forms on other planets would be the same as we have at national parks in the US stay on the designated trails, leave no trace, pick up your garbage. They would want as little impact on the national environment and ecosystems, to keep it healthy and pristine.