03 October 2011


How many remember the oxygen cycle from high school or college biology? According to Wikipedia, it is "the biogeochemical cycle that describes the movement of oxygen within its three main reservoirs ~ the atmosphere (air), the biosphere (the global sum of all ecosystems), and the lithosphere (Earth's crust)." Of particular interest to nearly all living things are the atmosphere and the biosphere, those regions where we have immediate access to oxygen. And both are in trouble. Oxygen is produced mainly through photosynthesis, by phytoplankton in the ocean and by forests on land (see map above, click to enlarge). Toxic human activity such as air and water pollution, coupled with global warming induced by homogenetic production of greenhouse gases, are reducing the presence of the very plants which sustain our breathing.

Justin Gillis in the NYTimes writes that as the climate warms, ecosystems are being exposed to stressors for which they have no adaptive response. As a result, forests around the globe are being consumed by everything from drought, pine bark beetles, and water stress to encroachment by humans. As global temperatures slowly rise, the future habitability of the Earth may be in peril. "Forests have been absorbing more than a quarter of the carbon dioxide that people are putting into the air by burning fossil fuels and other activities. It is an amount so large that trees are effectively absorbing the emissions of all the worlds cars and trucks [but are unable to absorb the remaining three-fourths of the carbon dioxide produced by humans]. Without that disposal service, the level of carbon dioxide in the atmosphere would rise even faster.

Yet the forests have only been able to restrain the increase, not halt it. And some scientists are worried that as the warming accelerates, trees themselves could become climate-change victims on a massive scale .... If forests were to die on a sufficient scale, they would not only stop absorbing carbon dioxide [and producing oxygen], they might also start to burn up or decay at such a rate that they would spew huge amounts of CO2 back into the air ~ as is already happening in some regions. That, in turn, would speed the warming of the planet, unlocking yet more carbon dioxide stored in once-cold places like the Antartic.

Scientists are not sure how likely this feedback loop is, and they are not eager to find out the hard way."

Gillis' entire article may be found here. Embedded in it are a video showing drought-induced forest fires in Arizona, and an interactive map showing the currently-forested regions of the globe (which are a shrunken remnant of the forests that existed before humans began to colonize and alter the landscape, especially within the past five hundred years).

The preservation, indeed the expansion, of wilderness and wildlife are not just issues for tree-hugging idealists. They are issues for pragmatic people everywhere. Life in Earth is an intricate web. You cannot interfere with one strand, without affecting other strands, and ultimately all living things.

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