BY DR. JOSE PALU-AY DACUDAO
(Why Chernobyl mammalian wildlife survive)
THUS FAR, we have examined how human activities that prevent plant products from getting oxidized (by getting biologically decomposed or burned) is a way to sequester carbon dioxide away from the atmosphere.
What about increasing the amount of photosynthesis going on the globe? What human activity by far is the most responsible for speeding up photosynthetic production worldwide?
Clue: Strictly speaking, it does NOT result in a net atmospheric carbon dioxide sequestration. On the contrary, it is the foremost emitter of anthropogenic carbon dioxide.
Yes, you’ve guessed it. Combustion of fossil fuels.
First there is an observational fact, which several papers have already noted. The surface of Earth has significantly greened by at least 20% since the 1980s. This is a short cut for saying that satellite imagery of brown areas on the planet (including large parts of the dry North American western continent, inland dry north east Eurasia, northern Africa) which lack surface photosynthetic plants have come to be covered by green colored surface photosynthetic plants. The phenomenon is massive and ongoing.
Why?
First consider that carbon dioxide for plants is food and fertilizer. Photosynthesis takes away carbon dioxide front the atmosphere and turns it into the solid bodies of the photosynthetic organisms. In the presence of carbon dioxide, plants grow faster. In addition, there is the way the stomata (little holes on a plant’s leaf that allow gases in and out) react to carbon dioxide. Stomata increase in diameter if there is less carbon dioxide in the air, in order to allow it into the inside of a leaf. As a corollary, stomata contract when atmospheric carbon dioxide increases, as the larger partial pressure of the gas now allows it to get inside the leaf even with the openings being smaller. But a larger opening means more volatile water can escape to the outside; and a smaller opening means less water escaping to the outside. The increase of carbon dioxide in the air contracts the stomata of leaves, thus decreasing the rete of water transpiration to the outside. This preserves water for plants, and subsequently allow them to populate and green up drier areas of the globe.
The main difference between the 1980s and the decades onwards is that the carbon dioxide level in the atmosphere has been steadily increasing. Thanks to the combustion of fossil fuels, and other anthropogenic activities such as calcining calcium carbonate minerals in order to make cement, and smelting iron, aluminum, magnesium and other metal oxides.
The parts of the planet that have now become more or less permanently green with the higher levels of carbon dioxide represents the biggest carbon sink that humanity has created (as long as they don’t get burned down or biologically decomposed permanently).
Never mind the dumbfoundingly dumb memes going around in the internet that the greening of planet Earth is bad. Trying to shoehorn faster plant growth, including that of food crops and tree plantations, and new plant growth in previous desert ecosystems, into something bad is something that always amazes me. (To be continued)/PN
