How exactly has our longevity caused an atrophy of our environment? I cannot see the cause and effect you are claiming here. There is not a corrolary between longer life and a population explosion. The developed world which has these longer projected lifespans also tends to have barrel-like population distributions (a stable population), whereas it is those countries who lack sufficient medical infrastructure, that see a population explosion. Families have more kids precisely because they don’t expect they will all survive to adulthood.
In regards to the future, by killing off the weaker members of our species, be they lesser in faculty of mind or facility of body, it is possible to restore the ecology of the planet and reverse the damage done on a global scale.
How exactly, is killing off the disabled, supposed to be a good thing? Especially as, as you point out, we can utilise our technology to remove this disability. We are removing sentient, self-aware minds for no purpose other than to support a hypothesis with no evidence, that somehow disabled individuals are bad for the planet.