We have all seen forests, and walked in them, shivered at the sound of the wind in the trees. They have appeared in our dreams, sometimes scared us. Forests cover a surface area of almost 4 billion hectares, or one third of land above sea level. They are familiar, yet mysterious. Defining them is not an easy thing to do.
What is a forest, exactly? When does a group of trees or a grove become a forest? What is a tree, for that matter, and what is the difference between a shrub (ziziphus, for example), giant bamboo (a variety of grass that grows to a height of 8 metres) and an oak tree? The simple questions are often the hardest to answer. Even the specialists disagree on the subject.
Despite such ambiguities, a definition is needed. The Food and Agriculture Organization of the United Nations (FAO) defines a forest as land occupying an area of over 0.5 hectare made up of trees that reach a minimum height of 5 meters at maturity, with tree crown cover of more than 10%.
However, this definition excludes the vast expanses of tundra around the polar circle, home to willow, birch and dwarf conifer whose growth is limited by the extreme climate conditions.
This definition also puts healthy forests on a par with degraded forests, and very rich primary (old-growth) forests with artificial forests, and includes oil palm and eucalyptus plantations, while some consider these as forest crops.
These are but a few examples: depending on the definition used, the area of forest land can triple, from 2.3 to 6 billion hectares. The wide diversity of situations reflects that of forests themselves. It is this diversity that we explore in this book.
Extract from the book « Of Forests and Men » written by GoodPlanet for he International Year of Forests, 2011