Its sad what we've done to the planet. I'm sure many (if not all) alien species (if they actually exist, although I believe they do) ran into the same problem. It may be the impossible ''Wall'' of the Fermi paradox that nothing can get past. Species may just corrupt their planet beyond repair before they have the science to understand the issue and stomp the brakes, and then don't leave the planet fast enough or unsuccessfully colonize other planets. It may already be too late.