There is an enduring connection within the human consciousness between forests and climate, whereby forests are understood to influence climate and that clearing the woods or planting trees changes climate. From several centuries, this idea exploded onto public awareness with the belief that clearing forests improved climate. The drive for climate betterment gave way to concern for a decline in rainfall as the forests were cleared, and the nineteenth century saw repeated calls in all reaches of the world to reforest denuded lands to increase rainfall. Meteorologists, however, dismissed an influence of forests on climate, and the science of forest meteorology was forgotten. Now, forests are again recognized for their climate benefits. Like our forebears, we again talk of purposely using forests to improve climate. Protecting existing forests, restoring degraded forests, and planting new forests are seen as critical to solving the climate problem. That the biosphere is fundamental to, not separate from, climate is a core tenet of the newly emerging Earth system science. This realization is not new. It is borne from the long, controversial chronicle of forests and climate change.

Forests regulate climate through exchanges of energy and materials with the atmosphere. The idea that forests affect climate is not new. A vigorous debate about deforestation, reforestation, and climate change began during European settlement of the Americas, spreading to all regions of the world before collapsing in the early 1900s. The story of forests and climate change is told as being scientifically wrong and advanced for political, economic, or cultural reasons, but it has not been told from a modern scientific perspective. In fact, it represents the foundation for the interdisciplinary study of Earth as a system. Many of the questions posed in today’s study of climate change and climate solutions have their origins in the forest-climate question. The multicentury controversy over forests and climate change is a narrative in which purposeful modification of climate is longstanding, but by felling or planting trees. Earth system science is a centuries old idea, conceived in the long-held belief that forests influence climate and doomed to fail by the disciplinary specialization of the sciences. Narrow-mindedness prevented a vision of the world as an interconnected system.