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This book supports learning about forest ecology. A good place to start is with a few points about knowledge, followed by a framework on how to approach forest ecology, some key features of using graphs to interpret information, and finally coming around to how to think about questions and answers in forests.

Humans try to understand complex worlds through a range of perspectives. Art tries to capture some essential features of a complex world, emphasizing how parts interact to form wholes. Religions explain how worlds work now, how the worlds came to be, and what will come next. Both art and religion develop from ideas and concepts, originated by individual artists or passed down by religious societies. How do we know if a work of art or an idea in religion represents the real world accurately? This question generally isn’t important. Art that satisfies the artist is good art, and religions are accepted on faith.

Art and religion have been evolving for more than 100 000 years, and lands and forests have been part of that development. One of the first written stories is a religious one from the Epic of Gilgamesh, from more than 4000 years ago from the Mesopotamian city of Uruk (now within Iraq). Gilgamesh and a companion traveled to the distant, sacred Cedar Mountain to cut trees. Lines from the epic poem include (based on Al‐Rawi and George 2014):

They stood there marveling at the forest, observing the height of the cedars … They were gazing at the Cedar Mountain, dwelling of gods, sweet was its shade, full of delight. All tangled was the thorny undergrowth, the forest a thick canopy, cedars so entangled it had no ways in. For one league on all sides cedars sent forth saplings, cypresses for two‐thirds of a league. Through all the forest a bird began to sing … answering one another, a constant din was the noise. A solitary tree‐cricket set off a noisy chorus. A wood pigeon was moaning, a turtle dove calling in answer. At the call of the stork, the forest exults. At the cry of the francolin bird, the forest exults in plenty. Monkey mothers sing aloud, a youngster monkey shrieks like a band of musicians and drummers, daily they bash out a rhythm …

And after slaying the demigod who protected the forest, Gilgamesh's companion laments:

My friend, we have cut down a lofty cedar, whose top abutted the heavens … We have reduced the forest to a wasteland.

What would actually happen if cedar trees were cut on a mountain? Would more cedar trees establish, would the post‐cutting landscape provide suitable habitat for the birds and monkeys? Would floods result? Anything could happen next in a story, but understanding which stories about the real world warrant confidence depends on the strength of evidence.

The core of understanding is knowing how one thing connects to another, and if the connections are the same everywhere and all the time, or if local details strongly influence the connections. The seasonal movements of the sun across the sky are consistent across years, but appear to differ from southern to northern locations. Multiple stories might explain the Sun's march with reasonable accuracy. Patterns etched on rocks by ancient artists may line up with key points in the Sun's seasonal patterns, and the movements of the Sun may reliably follow ceremonies convened by a society with the goal of ensuring the Sun's path. With art and religion, people may have understood the movement of the sun through the year was actually caused by the etchings on rocks or by ceremonial rites. These ideas may or may not have been true, but stories do not have to be true to be useful. Stories can persist as long as they are not so harmful that a society would be undermined. This idea is the same as genes in a population; natural selection does not aim toward retaining the best genes across generations, it only tends to remove genes that are harmful.

The human drive to understand cause and effect entered a new dimension when the notion developed of trying to figure out if an appealing idea might be wrong. Ideas of Newtonian physics and especially relativistic physics not only chart the apparent movement of the sun with more precision than would be possible from rock etchings or ceremonies, they also would be very, very easy to prove to be wrong. A deviation as small as one part in one million could prove the expectations of physicists were wrong. This innovation of science, based on investigating if an idea is wrong, developed very slowly alongside art and religion, and then exploded over the past four centuries to change the world.

Scientific thinking comes with two parts: creative new ideas about how the world works, and tough challenges that find out if the idea warrants confidence. Clearly most of the creative new ideas that scientists developed were wrong, either fundamentally or just around the edges. The ideas that withstood the challenges of testing have transformed the planet, feeding billions more people than our historical planet could have fed, sending machines across the solar system, and giving us an understanding of how our atoms formed in a collapsing star and how those same stellar reactions can be harnessed to obliterate cities. The idea that investigating whether an idea might be wrong has proven to be the most powerful insight humans have ever developed.

Returning to forests, trees and forests continue to be parts of art, religion, and science. When it comes to the scientific understanding of forests, both parts of science are needed: the generation of creative ideas and the challenging of those ideas to see if they warrant confidence. How do creative ideas about forests arise? That complex question has no simple answer, though creative ideas might arouse observation, learning, thinking, and pondering. The second part is more straightforward; once an idea is expressed, the hard work can begin on challenging the idea, to see if it's a better idea for accounting how forests differ across space and time.

A key point in science is being clear on which of these two aspects is being developed. The generation of a creative idea should not be mistaken for a reliable, challenge‐based conclusion. Challenging an existing idea is important, though real gains in insights might depend on new ideas and new methods of measuring and interpreting.