The earth will continue to exist with or without humanity.
The ecosystem will adapt to any changes of environment with or without humanity, until the sun begins to die.
Therefore neither the Earth nor the ecosystem are in need of any help from humanity.
A change in the ecosystem so that it becomes less favorable for humanity won’t kill off all of humanity.
Environmentalism is therefore superfluous to the future existence of the earth, the ecosystem and humanity, assuming that environmentalism is not necessary for the construction of the sustainable inter-Solar system capsule before the sun begins to die.