Why is the destruction of the earth's forests thought to be contributing to global warming?

Answer 1

There are many reasons why the destruction of the earth's forests can contribute to global warming. Probably the most prevalent of the green house gases released by industry, Carbon Dioxide, is primarily removed from the atmosphere by plant life. Through photosynthesis, any plant takes in Carbon Dioxide, Water, and Sunlight and creates glucose. It can then use this glucose as food, or convert it into other usable forms (fiber - wood, starch - potato). In this way the plants capture and store the Carbon Dioxide. By burning a tree, you will release nearly all of the Carbon Dioxide it has removed from the atmosphere. On top of that, you lose the trees ability to remove Carbon Dioxide from the atmosphere.

Trees and forests also prevent water from stagnating, in stagnant water, bacteria and fungi break down various organic compounds in the soil (the remains of dead organisms) and release lots of different gases, Carbon Dioxide being one of them, and methane, another potent greenhouse gas another.

So basically by removing forests you stop the absorbtion of CO2 from the atmosphere, by burning the tree (if that is how they are clearing the forest) you release all of the CO2 it ever absorbed in its life, and you also increase the amount of CO2 being released in some cases, due to environmental reasons.

Answer 2

A secondary effect (in addition to the chemical analyses given previously) is that the change from trees to pavement causes a localized rise in average yearly temperature. Here's a case history that makes this point.

In 1900, the Santa Clara Valley of California was the most fertile, productive agricultural region in the world, with orchards extending over thousands of square miles of alluvial soil (as much as 40 feet of topsoil in places).

Beginning in the 1950s with the postwar industrial boom, the Santa Clara Valley gradually changed from rural to suburban, but there were still thousands of acres of orchards. As the area grew, however, the orchards were removed and replaced with streets, homes, and businesses, which required large parking lots for customers and employees. By the 1970s, when this area became known as the Silicon Valley (instead of the Valley of Heart's Delight, as it was known in the 1920s), there were only a few hundred acres still planted with fruit trees.

By the 1990s, the last of the old orchards in Sunnyvale were being torn down -- in part because the property value of the land was too high to keep it in use for fruit trees, but most important because the cherry trees (owned by the Olson family, one of the area's first settlers a hundred years before) were succumbing to the climate change.

Cherry trees, it turns out, require a certain number of days each year at a low temperature -- I believe it was at least 30 days below 40 degrees F but I can't recall exactly. Without this period of winter dormancy, they age quickly and bear small yields of fruit -- like a human deprived of sleep for too long, they sicken and eventually die.

In the early 20th century, the Santa Clara Valley had no problem maintaining this cold period, but by 1990, the temperature had risen to the point where the cherry trees were dying off. The arborists that I spoke to specifically pointed to the rise in temperature due to the paving over of so much of the land with asphalt, which absorbs heat during the day and reflects it back at night. The net result is that land which had once been covered in trees, and stayed cool, was now covered in asphalt and concrete, and stayed hot.

So every acre of land that is deforested and then paved (which are two different things, of course) contributes to a localized increase in average annual temperature -- sure, it's localized, but multiply it by several million acres a year and the effect becomes catastrophic. And this doesn't include the human activity that invariably follows the urbanization (or suburbanization) of an area, which adds even more to the thermal load with cooking, heating, energy consumption, and more.

If you have trees -- keep them. If you don't have trees -- plant them.

Answer 3

Most forests are cleared by means of cutting and burning. A by product of burning (combustion) is carbon dioxide, which is considered to be a "greenhouse" gas. Thus large scale burning releases huge amounts of this gas where it normally would not be given off. Also plants convert CO2 into oxygen so fewer plants mean less CO2 is being converted.

How much of a problem this actually is can be debated, but that's the reasoning.

Answer 4

Trees absorb CO2 in the process of photosynthesis thus reducing the amount of CO2 in the atmosphere. They produce O2 during that same process. When the trees are removed less CO2 is taken out of the atmosphere thus remains to create the greenhouse effect that is theorized to be causing Global Warming.

Answer 5

plants 'consume' CO2 to photosynthesise, releasing oxygen into the atmosphere;
CO2 + H2O -> C6H12O6 + O2 using energy from the sunlght.
cutting down the trees is reducing the amount of carbon dioxide removed from the atmosphere per unit time. remember, animals use oxygen, release carbon dioxide, so there's a balance of oxygen and carbon dioxide that's being disrupted. now carbon dioxide is quite heavy, and doesnt rise too quickly because of that. it absorbs a lot of heat and stays down here with us a good while. when it does rise, it eventually blankets us, allowing sunlight to enter the atmosphere, strike the earth, get converted to heat, and when this heat rises, it meets the blanket and is trapped. so the heat accumulates and average global temperature rises. his is global warming.