Closed canopy forests are amazing ecosystems, full of strange species and huge variations, many of which have yet to be identified. The forests are found in a wide variety of environments -- polar, temperate and tropical -- and locations. However, these fascinating places are also being threatened by climate change and the expansion of human civilization, so all of their secrets may never be discovered.
A closed canopy forest is a dense growth of trees in which the top branches and leaves form a ceiling, or canopy, that light can barely penetrate to reach the forest floor. Despite their close proximity, the branches rarely touch directly. The limited sunlight reduces the amount of vegetation growing under and between the mature trees, leaving the ground mostly free of brush.
Closed canopy forests can form anywhere there are enough trees, and can be deciduous or coniferous. Some of the largest examples of closed canopy forests are found in the rain forests of Ghana and Brazil, although the southern parts of the taiga (a coniferous forest that covers large portions of Canada, Alaska, Mongolia and Sweden.)
The closed canopy areas of the rain forests are home to numerous species that exist nowhere else on Earth. This includes many types of plants, including species of bromeliads, liana and epiphytes, as well as insects and animals. Some species of birds, sloths, lizards and frogs never leave the canopy, and thousands of species of insects live only in the trees. Some scientists estimate that the species identified so far are only a tiny portion of those who live in closed canopy forests.
Although many things affect the huge forests on this planet, the two greatest threats are human encroachment and global warming. As the human population expands, people cut down larger swaths of forest to plant fields and to use the lumber for many purposes. The forests are unable to regrow quickly enough to replace the cut sections, and so continue to shrink. The effect of global warming is most obvious in colder climates, where plants and animals adapted to the temperatures are unable to cope with warmer weather and are forced to leave their habitats or die.