Forests are being cut down all across the world, but there are two different kinds of forests. The first is the temperate forests, which are located further north and usually coniferous. Loggers in these areas threaten the best remaining habitat of the Wolf and Grizzly bear. Not only this, but many temperate forests are lumbered in ways that do not protect the soil. The result is that silt and nutrients are flushed out, polluting streams and reducing the regenerative capacity of the forest. Like the whale, forests are harvested with too little concern for sustainable yields of timber and too much conern for maximizing the stream of income from the resource.
However, it is the fate of the tropical forests that will greatly determine the biological wealth of earth in the future. These ecosystems are the single greatest reservoir of biotic diversity on the planet. About two-thirds of all species in the tropics occur in the rainforests. About two-fifths to one-half of all species on earth occur in the rainforests, which cover only 6% of the earth's land surface. And these reservoirs remain mostly uncatalogued: only about 15% of their species have even been named, and little is known about their biology. Naturalist Peter Raven has pointed out, "Billions of dollars have been spent on 
the exploration of the moon, and we now know far more about the moon than we do about the rainforests of say, western Colombia. The moon will be there far longer than these forests…"
The loss of the forests have been estimated at 25 acres per minute between 1975 and the year 2000. This comes to about thirteen million acres of forest lost per year. The biotic diversity, or the numbers of populations and species, will disappear much more rapidly than the forests themselves. At present rates, nearly all the lowland forests of the Philippines, peninsular Malaysia, Indonesia, and Southeast Asia will have vanished by the turn of the century.
Habitat fragmentation will also cause extinctions of many organisms that require large areas for survival or are sensitive to the impacts of disturbance and pollution. It is estimated that a catastrophic loss of species and populations will have occurred within fifteen to twenty years, and the majority of rainforests species would have disappeared within thirty to fifty years.
The pressures of rainforest loss come primarily from farming, lumbering, ranching, and cutting for firewood. In the rainforests, when one tree is felled, it drags down many of its neighbors with it. A broken branch may sometimes signal the start of a lethal attack by bacteria, fungi, or insects. Furthermore, large areas of the forests are damaged by the dragging of logs, the building of roads to haul timber away, and the creation of depots for stockpiling them. And finally, ranching is a great cause of deforestation, because large tracts of land are being converted to rangeland for the grazing of cattle. In the twelve year period prior to 1978, 30,000 square miles of Amazon land in Brazil were cleared to make room for 336 ranches with 6 million head of cattle.
Indirect Causes - Pollution
