Harry Potter and the End of Trees
That's how the Daily Show jokingly referred to the last volume, the 870-page opus Order of the Phoenix. Luckily, the just-about-to-release Half Blood Prince is a tad lighter at just 672 pages. Still, with so many hardcover and softcover editions in print, that's a whole heckuva lotta trees. And if you want a sustainable Voldemort, you need to look to Canada, according to this NYTimes article (originally sourced at Treehugger):

As part of a growing worldwide campaign that is prompting a shift in the publishing industry, environmental groups, including the National Wildlife Federation and Greenpeace, are asking Potter fans in the United States not to buy Scholastic's editions and instead to order the new title online from Canada, where the publisher, Raincoast Books, has printed the book on 100 percent recycled paper. Scholastic says it does use some recycled paper for its books, including the Potter series, but it would not divulge the amount. [...] It is not clear what effect, if any, a boycott would have on Scholastic, which is planning an initial print run of almost 11 million copies. Raincoast would not disclose the size of its print run, but it printed more than 900,000 copies of the previous installment, "Harry Potter and the Order of the Phoenix," also with 100 percent recycled paper. (The cost of ordering the book from Canada on Amazon.ca is about $2 more, not including potential extra shipping costs, than the cost on Amazon.com.)

Mrs. F and I have opted for the "adult UK edition" of Half-Blod Prince from Amazon UK (which offers a more serious, "grown-up" illustrated cover and the promise of someone uttering "Bollocks!"; also, it's just nicer to have the true Englishness of the language from the characters, rather than the sanitized-for-Americans US versions). I guess I'm part of the problem, without much hope of recycle paper for this edition plus adding to global warming with shipping it from across the globe. I might just have to assuage my guilt with another trip to Climate Care's air travel CO2 off-set programme.