Rainforest and global warming.

I found some disturbing data:
rainforest shrinking faster

Brazil's Amazon rain forest - one of the most biologically productive regions on the planet - is disappearing twice as fast as scientists previously estimated.

That is the stark conclusion ecologist Gregory Asner and his colleagues reached after developing a new way to analyze satellite images to track logging there.

rainforest and global warming

Tropical Rainforests:

Act as a kind of "heat pump", redistributing solar radiation from the equator to temperate zones. This function warms temperate zones while cooling the tropics.

Cause large amounts of water to evaporate into the atmosphere. These huge amounts of water generate clouds which reflect sunlight back into outer space, thus cooling forested regions.

Play a major part in regulating the flow of freshwater through the ecosystem, which in turn significantly affects local and regional precipitation patterns. Researchers fear that this disruption of the water cycle could lead to a drying out of the remaining forest cover.

Is it possible that the increasing strenght of the hurricanes is related to the disappearing of the rainforest?

Between 5,000 and 10,000 years ago the Amazon rain forest did not exist. It was a savannah with isolated pockets of forest. Changing climate and human use patterns allowed the tree cover to expand and cause the savannah ecosystem to disappear. So is returning to its previous state a desirable condition? Or was the previous ecosystem the unacceptable condition?

It all depends on your point of view.

I don't know man, but this is something that is a real point of concern.

You cannot argue the envionrmental importance of the Amazon Rainforest. I'm just surprised at the "worse then we thought" news.

Originally posted by dave_54
Between 5,000 and 10,000 years ago the Amazon rain forest did not exist. It was a savannah with isolated pockets of forest. Changing climate and human use patterns allowed the tree cover to expand and cause the savannah ecosystem to disappear. So is returning to its previous state a desirable condition? Or was the previous ecosystem the unacceptable condition?

It all depends on your point of view.

You just described why protecting the Amazon is absolutely vital. Over thousands of years the Amazon rain forest gradually locked in enormous amounts of carbon and became the largest rain-forest yet we are releasing that carbon back into the atmosphere as carbon dioxide at a much faster rate, faster than anything on the planet can absorb.

Originally posted by orca71
You just described why protecting the Amazon is absolutely vital. Over thousands of years the Amazon rain forest gradually locked in enormous amounts of carbon and became the largest rain-forest yet we are releasing that carbon back into the atmosphere as carbon dioxide at a much faster rate, faster than anything on the planet can absorb.

The carbon buffering of the oceans is several orders of magnitude greater than of terrestial forests. And of the forests, old growth forests are carbon neutral, releasing as much as they absorb. In late senescence, old growth forests are a net carbon emitter as decay exceeds growth. Carbon sequestration of forests is greatest where the forest is actively managed, harvested and replanted. There are many reasons why forests should be maintained, but carbon sequestration is not among them. Even under the best of conditions, the role of forests is relatively minor in the global carbon cycle. The small role that forests provide is from actively managed forests, not untouched preserves.

Originally posted by dave_54
The carbon buffering of the oceans is several orders of magnitude greater than of terrestial forests. And of the forests, old growth forests are carbon neutral, releasing as much as they absorb. In late senescence, old growth forests are a net carbon emitter as decay exceeds growth. Carbon sequestration of forests is greatest where the forest is actively managed, harvested and replanted. There are many reasons why forests should be maintained, but carbon sequestration is not among them. Even under the best of conditions, the role of forests is relatively minor in the global carbon cycle. The small role that forests provide is from actively managed forests, not untouched preserves.

The net CO2 output of a mature forest is a minor issue at best. A much larger issue is not in day to day net carbon emission but the fact that with each tree destroyed the carbon in the tree is released.

Every tree is made of x amount of carbon. Every tree that is destroyed releases x amount of carbon. Therefore destroying trees that were already there and will not be grown back as in the case of the Amazon and any other forest thats being destroyed releases x times the number of trees destroyed.

Thats an enormous amount of carbon being released. It takes thousands of years for a forest as large as the amazon to develop and in doing so locks in a tremendous amount of carbon. Yes, after a while, if the forest stops expanding, its net carbon intake can at times be zero or slightly negative but thats so minor its not worth mentioning, in fact the overall exchange is basically even.

What is worth mentioning is the reversal of the forest expansion. Forest expansion causes enormous amounts of carbon to be stored as trees. Reversing the process releases that carbon back into the atmosphere. Whats even worse is when that reversal of expansion, better known as deforestation, it takes place in a fraction of the time the original expansion took place.

Its estimated that about a Billion Tons of CO2 is released as a result of this process every year. A net increase of a Billion tons every year is a lot of trees. In the past the ocean might have been able to handle occasional spikes or fluctuations of this scale or even larger without showing too many negative symptoms, but unfortunately this is a continuous and accelerating phenomenon.

As for the ocean's role in the carbon cycle, in net terms, if we say 90% or even more of the CO2 removal is due to the ocean, then its apparent than a warmng ocean is a big problem. A warming ocean threatens phytoplankton, and phytoplankton is not only crucial to supporting the oceans food-chain but also for CO2 absorption.

It should be no surprise that the planet is now warming faster than at any time in the last 10,000 years, and that the rate of change is accelerating.

[edit on 22-10-2005 by orca71]

[edit on 22-10-2005 by orca71]

The total biomass of the Amazon rain forest represents about 0.000002% of the total planetary carbon (~3x10^17 tons), the vast majority is in the earths crust in the form of carbonate minerals like limestone (interesting side note -- Does global cement production release more net carbon than deforestation? That would be an interesting research project).

Land clearing in the Amazon is primarily for agricultural production, where the resulting crops would be a partial buffer against the carbon released by the land clearing. The exact net amount of carbon loss would depend on several factors, i.e. type of crop, forest type prior to clearing, agricultural practices, etc.

Global warming is a product of several factors, and greenhouse gases is only one of the factors. CO2 is only one of many greenhouse gases and is not even the main one at approximately 3.6% of total GHG. Of that 3.6%, about 3.2% is human created, the rest being natural. The amount of net carbon released by land clearing in the Amazon has a miniscule effect on total global warming.

As I mentioned in my earlier post there are many reasons to maintain tropical forests -- species diversity, the effect on continental rainfall patterns, and even a non-altruistic reason. Most of the land clearing in Brazil is for one crop -- soybeans. Brazil is rapidly becoming a major exporter of soybeans and is negatively affecting the U.S. soybean export market and global prices. Those pesky Brazilian farmers are hurting the U.S. trade balance and farm exports.

So we have many reasons to be concerned about land use practices in the Amazon basin. But the effect on global warming is wwaaayyy down the list.