Earlier this month, Penguin began a campaign to promote the Nature Conservancy's "Plant a Billion Trees" campaign by distributing a bookmark (printed on recycled paper, natch) that promotes three Penguin Classics with environmental themes: Rachel Carson's Under the Sea Wind, John Muir's The Mountains of California or Ralph Waldo Emerson's Nature and Selected Essays, along with the Conservancy's efforts to restore the Atlantic Forest of Brazil, one of the world's most biodiverse regions. So far the campaign has planted nearly 220,000 trees—and every dollar donated to the conservancy will put another tree in the ground.

Penguin is also undertaking its own green initiatives, with the stated goal of "becoming climate neutral by 2009."