-The destrucion of forest.

At present, the forests that still stay cover scarcely a fraction of the area covered by forests only hundred years behind. And the speed of destruction is increasing. Quite, up to the effects of the climatic change, they are threatening the existence of the last natural remaining forests.

When a forest is cut and new trees are sowed a plantation of few classes of trees does not give support to so many forms of life as a natural forest. These plantations will not produce a lot of wood of the highest quality. The trees in the natural forests have been growing during hundreds, and sometimes thousands, of years. The sowed trees are cut a few years after having being planted.

The human beings have been destroying the forests per centuries, but the rate of destruction has been increasing so rapidly that some forests will not last for much any more time.

The trees are cut not only by his wood and other products, but the area can be turned then for the cattle and in fields to feed a number of persons. As the cities become big, the forests are eliminated to allow the construction of housings, malls.

Nowadays only they preserve 20 % of the primary forests that were covering the terrestrial surface; nonetheless(though) there stay two third parts of the terrestrial biodiversity and are one of the major sinks of carbon of the planet.

http://www.jmarcano.com/nociones/bosque/threat.html

http://www.elecolo.com/?p=1871