One reference for the global oxygen cycle is Schlesinger, W. H. Biogeochemistry: An Analysis of Global Change. I will use numbers from the 2nd edition-
The atmosphere contains 3.7 X 10^19 moles of O2. Biotic fluxes are about 8 X 10^15 moles per year. So all of the earth's biota annually exchange about 1/4000 of the atmospheric O2. Another way of looking at this is to compare concentrations of O2 with the amount of CO2 available in the atmosphere for photosynthesis. The atmosphere is approximately 20.946% O2 and 0.038% CO2. If the amazon or the entire flora of the earth were to suddenly take up all of the CO2 in the atmosphere by photosynthesis, it appears to me that this would liberate enough O2 gas to raise the concentration to 20.984%, a trivial relative change. In other words contemporary photosynthesis has little to do with the fact that we have large amounts of O2 in the atmosphere. The O2 in our atmosphere is due to photosynthesis across 100s of millions of years and per Schlesinger is is balanced by the storage of pyrite and organic C in the earth's crust not by contemporary biotic carbon. Max Taub William Silvert wrote: > I think this is a common problem, not just for the Amazon. A nature > conservancy I have visited in a mangrove area claims that 95% of all primary > production comes from mangrove swamps. It would help to have a reliable > source for the general questions of where regeneration of oxygen occurs, > where pharmaceuticals come from, and so on. > > Bill Silvert > > ----- Original Message ----- > From: "SUBSCRIBE ECOLOG-L Jacob Lowe" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Tuesday, April 24, 2007 4:16 PM > Subject: Amazon Rainforest "facts" > > > >> Greetings everyone, >> >> As many of you know, I've spent the last year speaking at schools across >> Texas on work that Projects Abroad is doing in the Peruvian Amazon at the >> Taricaya Research Center. During my presentations, I like to give a quick >> "overview" of some of the encyclopedia-style "facts" about the Amazon, >> like >> biological diversity estimates, deforestation estimates, "tropical >> pharmacy >> to the world", etc at the beginning of the presentation. These statements >> have included the following "facts" that I've retrieved from websites like >> www.rain-tree.com, which does not cite any sources: >> >> 1. The Amazon Rainforest has been described as the "Lungs of our Planet" >> because it provides the essential environmental world service of >> continuously recycling carbon dioxide into oxygen. More than 20 percent of >> the world oxygen is produced in the Amazon Rainforest. >> >> 2. Currently, 121 prescription drugs currently sold worldwide come from >> plant-derived sources. And while 25% of Western pharmaceuticals are >> derived >> from rainforest ingredients, less than 1% of these tropical trees and >> plants >> have been tested by scientists. >> >> 3. The U.S. National Cancer Institute has identified 3000 plants that are >> active against cancer cells. 70% of these plants are found in the >> rainforest. Twenty-five percent of the active ingredients in today's >> cancer-fighting drugs come from organisms found only in the rainforest. >> >> The more I read these claims, the more uncomfortably I am repeating them >> to >> students without any assurance of their accuracy. Can anyone here >> elaborate >> on some of these claims? For example, I've read where statement (1) is a >> myth, and rainforest plants don't actually contribute any significant net >> increase in atmospheric O2. For claim number (2), I'd like to know >> specifically which drugs come from the Amazon. Number (3) I'm having >> little >> luck from the U.S. Cancer Institutes's website. >> >> Most importantly, I'm having little luck getting sources from >> www.rain-tree.com. >> -- Daniel Taub Assistant Professor of Biology Southwestern University 1001 East University Ave Georgetown TX 78626 USA Phone: 512 863-1583 Fax: 512 863-1696 [EMAIL PROTECTED]
