On the other hand, when forests are burned or logged and the debris left to decay, carbon dioxide is released into the atmosphere. Prevention of Flooding, Soil Loss and Siltation Tropical rainforest soils are very old and have been impoverished by eons of high rainfall leaching away their mineral nutrients. The forests have evolved to cope with this by rapidly recycling nutrients. Forest litter, and the droppings and remains of animals are quickly decomposed, releasing nutrients for uptake. Most nutrients are only available from this decomposing layer, so many rainforest trees are shallow-rooting and have buttresses for support.
Rainforests act like giant sponges, soaking up moisture, and then releasing it slowly.
This moderates the flow of rivers thus preventing flooding and ensures that rivers and creeks continue to flow during periods of lower rainfall. When the forest is cleared, rain falls directly onto the compacted soil, often resulting in serious soil-erosion, siltation and flooding. Major floods in southern Thailand, Bangladesh and the Philippines have been attributed to forest clearance. Once the nutrient recycling-system is broken down, the land can't support human activities such as cattle ranching for more than a few short years. Tropical Rainforests are Absorbers of Carbon Dioxide Scientists now say that the rainforest ecosystem in the Brazilian Amazon is a net absorber of carbone dioxide, and therefore helps to protect the earth against the greenhouse effect.