conservation of habitats (rain forest)

Robin Carrier
Tue, 27 Dec 2011 10:39:41 PST

i  also have always thought trees provide oxygen and hece just looked it up 
and found among  many othere  things:

"A single mature tree can absorb carbon dioxide at a rate of 48 lbs./year 
and release enough oxygen back into the atmosphere to support 2 human 
beings." - McAliney, Mike. Arguments for Land Conservation: Documentation 
and Information Sources for Land Resources Protection, Trust for Public 
Land, Sacramento, CA, December, 1993

"On average, one tree produces nearly 260 pounds of oxygen each year. Two 
mature trees can provide enough oxygen for a family of four." - Canada's 
environmental agency, Environment Canada

 there must be an xplanation.

robin carrier
----- Original Message ----- 
From: "lou jost" <>
To: <>
Sent: Tuesday, December 27, 2011 1:27 PM
Subject: Re: [pbs] conservation of habitats (rain forest)

Peter, while forests are really important for regulating the water cycle and 
storing carbon, they have virtually nothing to do with oxygen generation or 
regulation. The idea that forests are the "lungs of the earth" or "make our 
oxygen" is a myth. Forests are approximately oxygen-neutral. They are also 
almost carbon-neutral, but they do have a vast store of standing carbon 
(accumulated over a long timespan) at any moment. This carbon is all 
released into the atmosphere when the forest is burned.

On the other hand, forests' role in water regulation is under-appreciated. A 
large fraction of the water that falls as rain in Amazonia has been recycled 
through trees multiple times, so western Amazonia would get much less 
rainfall if the Amazonian rain forest were reduced. Trees reduce runoff; if 
the trees were not there, water would go quickly and directly into rivers 
and then to the ocean, rather than being taken up by the vegetation and 
transpired. This also makes for more stable rivers that flood less often and 
do not dry up as often. Also, in cloud forests, water condensing or 
collecting on tree leaves is an important source of "rain"; this rain only 
falls inside the forest. This kind of "rain" keeps many rivers alive during 
dry seasons, and many cities depend on such streams. The streams would 
disappear without the forest.
Lou Jost

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