I discuss this question in my new book "Savng Gaia". How do humans save the planet? What needs to be done? The main problem to be addressed is mankind's antropocentricism, placing humans at the center of everything. As a former biology teacher, I can safely say, humans are just another animal and we better learn that fast as Gaia is approaching the tipping point. We are in the Holocene Extinction and more than half of all vertebrates from the time I was born, I'm 74, are gone forever.
As far as the meaning of life goes, let's take the advice of the great physicist Niels Bohr. There is no meaning to life. What purpose or meaning can the universe have when everything winds up in a black hole. The universe just is. Humans have to give it meannig.