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Name: Jessica 
Status: other 
Grade: other 
Location: FL 
Country: N/A
Date: 9/2/2005

I have a college professor that claims trees are not as neccasary to the atmosphere as we think because most of our oxygen comes from bacteria in the ocean. How true is this and how much of our oxygen comes from land plants?


It is perfectly all right to ask your professor to direct you to some references on this topic. A discussion with him or her will also allow you to make sure that he is not misunderstood with regard to the facts and also their implications.

Regarding your question, it is true that most of the earth's oxygen production, PERHAPS as much as 90%, is from the sea plants through photosynthesis within the top 100 m of the ocean water where there is enough sunlight for the process to take place. But the implication that somehow trees are not necessary (to atmosphere and perhaps by implication to life) is unwarranted. To state that, we have to fully understand the entire ecosystem, be able to model it, validate the model going back in time, and then cautiously applying it to predict and verify future trends.

The ecosystem that supports life on earth is a very delicate, our knowledge of it negligible, and we are not in a position to state what facets of the ecosystem are necessary and which ones are not. One approach to ecosystem management - if we can all it so - is to avoid causing dramatic man-made changes until we understand the system better. The other school of thought, driven mostly by ideological and financial considerations, states that undertaking activities that cannot be shown to cause damage is fine.

Ali Khounsary, Ph.D.
Argonne National Laboratory

The professor may have meant what he/she said. The short response to the assertion is, "Please, show me your data." The data (in the most generous appraisal) is confounding, because no one knows. Climate change is (call it the greenhouse effect if you want) has become highly politicized. On the one hand, there is the grossly oversimplified position: Fossil fuels when burned produce CO2; CO2 is a greenhouse gas; therefore the average temperature of Earth will increase with disastrous consequences. On the other hand, there is the unsubstantiated "no problem" position characteristic of the burn-the-forest assertion. Global warming (the greenhouse effect) is not well understood (that is being kind). First, the various numersou computer models give conflicting results because the input data are insufficient and/or not well defined. The classic example is the very term "average global temperature". Despite its common use, it is meaningless. The climatic condition cannot be characterized by a single number. A better concept is a "global temperature fingerprint", that is, some places are going to get warmer, others are going to get colder.

But no such "fingerprint" exists. Second, WATER (H2O), not CO2, is the major "greenhouse gas" and many models do not take water into account and so are doomed from the start. The condition of the climate depends upon several interacting positive/negative feedback cycles (H2O, CO2, sea ice, marine biology, terrestrial biology and hydrology, other atmospheric chemicals e.g. methane, solar insolation, solar "events", and other upper atmospheric effects, global lightning patterns, particulates and gases both from human origin and 'natural' origins such as volcanoes, even cosmic rays). Each is complex in its own domain. Some of these cycles (and others not mentioned) humans can have an impact; on others cycles, there is no control. See "Understanding Climate Change Feedbacks" National Research Council report. It is accurate to say that the "burn fossil fuel-produce CO2-increase global temperature" is so primitive a paradigm it is useless and meaningless, despite its popular use and appeal. At present, climate models are not even able to reconstruct climate history, much less predict the future. Chapter 10 of Philip Ball's book "Designing the Molecular World" gives a balanced statement of the state of affairs with respect to global science.

This is not to be taken as "anti-environmental" or "anti-conservation". Take it to mean that we need to ask the right questions, identify the proper variables, construct meaningful models. In fact, we don't need all the scientific data and predictions to "take care of mother Earth, it's the only one we have." We need to be honest about the state of our knowledge and understanding, however. And that state is very uncertain. Absurdly oversimplified models, like the "burn fossil fuel-produce CO2-increase global temperature" one are not constructive, to put it mildly. It focuses on only one of many interacting feedbacks that define "climate".

Vince Calder

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