Deforestation and the Hydrologic Cycle

Tropical  deforestation also  affects the local climate of an area  by

reducing the evaporative cooling that takes place from both soil and plant life. As trees and plants are cleared away, the moist canopy of the tropical rain forest quickly diminishes. Recent research suggests that about half of the precipitation that falls in a tropical rain forest is a result of its moist, green canopy. Evaporation and evapotranspiration processes from the trees and plants return large quantities of water to the local atmosphere, promoting the formation of clouds and precipitation. Less evaporation means that more of the Sun's energy is able to warm the surface and, consequently, the air above, leading to a rise in temperatures.

Deforestation and Biodiversity

Worldwide, 5 to 80 million species of plants and animals comprise the "biodiversity" of planet Earth. Tropical rain forests-covering only 7% of the total dry surface of the Earth-hold over half of all these species. Of the tens of millions of species believed to be on Earth, scientists have only given names to about 1.5 million of them, and even fewer of the species have been studied in depth. Many of the rain forest plants and animals can only be found in small areas, because they require a special habitat in which to live. This makes them very vulnerable to deforestation. If their habitat is destroyed, they may become extinct. Every day, species are disappearing from the tropical rain forests as they are cleared. We do not know the exact rate of extinction, but estimates indicate that up to 137 species disappear worldwide each day. The loss of species will have a great impact on the planet. We are losing species that might show us how to prevent cancer or help us find a cure for AIDS. Other organisms are losing species they depend upon, and thus face extinction themselves.

After Deforestation

What happens after a forest is cut is very important in the regeneration of that forest. Different cutting techniques and uses of the land have diverse effects on the ground and surviving organisms that make up a rain forest.

In a tropical rain forest, nearly all of the life-sustaining nutrients are found in the plants and trees, not in the ground as in a northern or temperate forest. When the plants and trees are cut down to sow the land, farmers usually burn the tree trunks to release the nutrients necessary for a fertile soil. When the rains come, they wash away most of the nutrients, leaving the soil much less fertile. In as little as 3 years, the ground is no longer capable of supporting crops. When the fertility of the ground decreases, farmers seek other areas to clear and plant, abandoning the nutrient-deficient soil. The area previously farmed is left to grow back to a rain forest. However, just as the crops did not grow well because of low nutrients, the forest will grow back just as slow because of poor nutrients.

After the land is abandoned, the forest may take up to 50 years to grow back. Another type of farming practiced in rain forests is called shade agriculture. In this type of farming, many of the original rain forest trees are left to provide shade for shade-loving crops like coffee or chocolate. When the farm is abandoned, the forest grows back very quickly, because much of it was left unharmed in the first place. After this type of farming, forests can grow back as quickly as 20 years. Other types of farming can be more devastating for forest regrowth. Intensive agricultural systems use large quantities of chemicals like pesticides and fertilizers. These chemicals kill a lot of the living organisms in the area, seeping into the soil and washing into the surrounding areas. On banana plantations, pesticides are used on the plants and in the soil to kill pest animals. However, these pesticides also kill other animals as well, and weaken ecosystem health. Banana plantations also use irrigation ditches and underground pipes for water transport, changing the water balance of the land. After the abandonment of a banana plantation, or other intensive agricultural system, it can take many centuries for a forest to regrow. A study in Indonesia found that when only 3% of the trees were cut, a logging operation damaged 49% of the trees in the forest. Yet, even with that much damage, the rain forest will grow back relatively quickly if left alone after selective logging, because there are still many trees to provide seeds and protect young trees from too much sun. Clearcutting is much more damaging to a tropical rain forest. When the land is commercially clear-cut and all of the trees removed, the bare ground is left behind with very little regrowth. Unlike when the farmer cleared the land, there are almost no nutrients left behind because all the tree trunks were removed. A clear-cut forest can require many years to regenerate-in fact, scientists do not know how long it takes for a clear-cut forest to grow back.

The Future

The deforestation of tropical rain forests is a threat to life worldwide. Deforestation may have profound effects on global climate and cause the extinction of thousands of species annually. Stopping deforestation in the tropics has become an international movement, seeking ways to stop the loss of rain forests. Because the loss of rain forests is driven by a complex group of factors, the solutions are equally complex. Simple solutions that do not address the nature of world economics and rain forest ecology have little chance of succeeding. The future requires solutions based on solving the economic crises of countries holding rain forests, as well as improvement of the living conditions of the poor people often responsible for deforestation.