Characteristics of woodlands and forests

Wooded environments

Forests often appear monumental and unchanging. This is, however, mostly an illusion caused by our short human perspective. The earliest green plants possessing both roots and tissues specially adapted for the transmission of water belonged to the Psilopsida, which gave rise to the ferns and fern allies. It is from the ancestors of this group, which arose in the Silurian (c. 440 million years ago), that all trees – both ancient and modern – are ultimately derived (see Fig. 1.1). Amongst the many evolutionary trends found within this group were tendencies towards the production of (a) tall trunks and (b) seeds from which young plants, including trees, could develop relatively rapidly. Tree ferns, cycads, maidenhair trees, conifers, palms and the very large number of broadleaved genera remain in our woodlands and forests to this day (further detail on past forests can be found in Chapter 9). The amount and composition of the world's wooded areas have changed continuously over geological time, sometimes more rapidly than at others, and continue to do so, helped especially now by human activities. This book is mainly concerned with understanding today's forests in that light.

Wooded land currently covers between 30–35% of the world's land surface (depending on what is counted as forest) or around 39–45 million km2.