Stephen C. Sillett is a real person who is really smart about trees. He likes to climb really high up into trees and study them. He knows a lot about how trees grow and how they help us by cleaning the air and giving us oxygen to breathe.
Stephen C. Sillett is kind of like a tree detective because he can solve mysteries about trees. He looks at the branches and the leaves and the trunk and the roots to figure out how old the tree is and what kind of life it has had.
Some trees are really tall and Stephen C. Sillett knows how to climb them using special equipment. He wears a harness and uses ropes to climb up high into the tree. Once he is up there, he can see things that we can't see from down on the ground.
Stephen C. Sillett has studied trees all over the world, from the rainforests in South America to the forests in Canada. He teaches other people about trees too, so that they can learn to love and protect our beautiful forests.