The carbon dioxide that industrial civilization spews into the atmosphere has dramatic consequences for life on Earth that extend beyond climate change. CO2 levels directly affect plant growth, in turn affecting any kind of life that depends on plants-in other words, everything. Greenhouse Planet reveals the stakes of increased CO2 for plants, people, and ecosystems-from crop yields to seasonal allergies and from wildfires to biodiversity. The veteran plant biologist Lewis H. Ziska describes the importance of plants for food, medicine, and culture and explores the complex ways higher CO2 concentrations alter the systems on which humanity relies. He explains the science of how increased CO2 affects various plant species and addresses the politicization and disinformation surrounding these facts. Ziska confronts the claim that "CO2 is plant food," a longtime conservative talking point. While not exactly false, it is deeply misleading. CO2 doesn't just make "good" plants grow; it makes all plants grow. It makes poison ivy more poisonous, kudzu more prolific, cheatgrass more flammable. CO2 stimulates some species more than others: weeds fare particularly well and become harder to control. Many crops grow more abundantly but also become less nutritious. And the further effects of climate change will be formidable.