Changes.

Fantuzzi, The Boschereccia (detail), 1810

Single trees are extraordinary; trees in number more extraordinary still. To walk in a wood is to find fault with Socrates's declaration that "Trees and open country cannot teach me anything, whereas men in town do."  Time is kept and curated and in different ways by trees, and so it is experienced in different ways when one is among them. This discretion of trees, and their patience, are both affecting. It is beyond our capacity to comprehend that the American hardwood forest waited seventy million years for people to come and live in it, though the effort of comprehension is itself worthwhile. It is valuable and disturbing to know that grand oak trees can take three hundred years to grow, three hundred years to live and three hundred years to die. Such knowledge, seriously considered, changes the grain of the mind.

Thought, like memory, inhabits external things as much as the inner regions of the human brain. When the physical correspondents of thought disappear, then thought, or its possibility, is also lost. When woods and trees are destroyed -- incidentally, deliberately -- imagination and memory go with them. W.H. Auden knew this. "A culture,"he wrote warningly in 1953, "is no better than its woods."

Robert Macfarlane, from The Old Ways: A Journey on Foot