Interesting topic, Angelzz.

Like your friend I am very passionate about the environment.
It often puzzles me that so many (Christians and Muslims alike) who believe that God created this world and that they are appointed to be guardians over his creation, seem to have so little motivation to be more active with regards to the environment.

It would be great to see the monotheistic faiths rise up to that challenge!
But overall I get the impression that it is mostly secular people who drive the environmental issues ... why not us???

This is not really about da'wah.
This is about being active, and really practising what we preach!!
Perhaps there are Muslim environmental activist groups, who can explain the religious reasons behind their activities? Your friend might find that useful.

Peace