A forest is an area of land that contains a high density of trees. Forests are the most common terrestrial ecosystem, covering about 30 percent of the earth's land area and containing about 80 percent of its plant biomass. The largest share of the world's forests is in the tropical latitudes, at about 45 percent, followed by those in the boreal, temperate, and subtropical regions. More than half of forested land area is contained in just five countries: Brazil, Canada, China, Russia and the United States.
Nearly half the world's forest area is still relatively intact, while about ten percent is in mostly unconnected fragments. The least fragmented are tropical rainforests and boreal coniferous forests, and the most fragmented include subtropical dry forests and temperate oceanic forests.