Online stores should start offering a discount on the online version of their books for ebook readers (hint hint Amazon).
Use this discount as a feature, but offer people the offer to pay regular non-ebook price, and the different goes towards planting trees. At first this will offset the loss in trees due to the regular book editions, but if the ebooks surpass the regular editions (a long time coming I think!), you will get a positive return back to the environment.
