"This is a book about nature and culture," Eric T. Freyfogle writes, "about our place and plight on earth, and the nagging challenges we face in living on it in ways that might endure." Challenges, he says, we are clearly failing to meet. Harking back to a key phrase from the essays of eminent American conservationist Aldo Leopold, Our Oldest Task spins together lessons from history and philosophy, the life sciences and politics, economics...