Books don't harm the environment, people harm the environment.
There is something about a paper book that a PAAD/Kindle (contrary to their name they are lousy at starting fires) and other electronic devices lack.
True, ebooks don't take up much space... however I had a wall of books in my bedroom which I called the 'insulating wall' - An ebook cannot give the same atmosphere as a wall of books. Nor act like a wall of insulation either
I have many volumes of books that were printed and bound in the middle to late 1800's... They have survived 100+ years more than a few I have read several times over and since they were printed slightly before my time, others had a chance to enjoy them.
I seriously doubt ebooks will last decades let alone a century. Some new format or program will come up to make your data obsolete. Just like all the video games from the 1980's and early 1990's are now pretty hard to play without supporting software.
Beta max died, VHS died (I have a largish library of VHS which is essentially useless without a decent player), 8-track is gone, Cassette tapes are gone... Each time a new technology comes in the old stuff becomes useless and if you want a library you can use you have to expend thousands of dollars to 'rebuild'.
I assure you, 15-20 years from now the publishing companies will formulate a new venue to make you have to rebuy all your favorite books. All because you and millions of others didn't want to be bothered with a technology that actually worked, and worked so well it was around for centuries.