The plant population is not a net producer of oxygen

 This article is an English translation (supported by DeepL) of the following Japanese article.

南米アマゾン熱帯雨林火災〔２〕: 本に溺れたい

　Let's recall "photosynthesis," which we learned in high school science courses (chemistry and biology). Plants use the energy of sunlight during the day, plus CO2 from the atmosphere and H2O from the soil, to produce carbohydrates (mainly glucose C6H12O6) and O2. That is the following equation.

CO2 + 2H2O → (CH2O) + H2O + O2

　Looking again at this equation, one CO2 molecule corresponds to one O2 molecule.

　On the other hand, the composition of the earth's atmosphere is 21% O2 and 0.039% CO2 (2012 values, science timeline). Even if the Amazon rainforest alone were to produce atmospheric oxygen, there is an overwhelming shortage of carbon dioxide, the raw material for oxygen production, isn't there? Therefore, the catchphrase "the Amazon rainforest produces 20% of the Earth's oxygen" is clearly false.

　From this point onward, please refer to the following article of the original for a detailed explanation.

Why the Amazon rainforest doesn’t really produce 20% of the world’s oxygen, by Katarina Zimmer (National Geographic / August 28, 2019)

　In the meantime, I will list the key points of this article in bullet form.

(1) If oxygen produced on land is limited to the area of the Amazon rainforest, it can be considered to be 16%.

(2) If the contribution of marine plankton (phytoplankton) is taken into account, it is 9%, or conservatively speaking, 6%.

(3) If we consider the respiratory function of trees (forests), that is, their role as consumers of oxygen, half of the oxygen they produce is consumed in the respiratory function.

(4) The remaining oxygen is consumed to decompose the dead organic matter produced by the rainforest, which means that the net oxygen production is zero. In other words, the contribution of the biological community, not only in the Amazon, to the oxygen concentration is zero net.

(5) In modern ecosystems, the production and consumption of oxygen are in balance, and the concentration of oxygen in the atmosphere can be considered to remain unchanged.

(6) The abundant stock of oxygen on the earth today is a legacy of billions of years of geological accumulation of the oceanic phytoplankton that produced oxygen and was trapped on the ocean floor before decomposing as organic matter.

(7) Rather, the Amazon Rainforest is a global air conditioner that contributes to the mitigation of global warming and climate change due to its significance in the absorption and fixation of CO2 from the atmosphere.

(8) It also contributes enormously to the preservation of biodiversity.

　With regard to global warming, there is often criticism that CO2 emissions from the enormous consumption of fossil fuels (coal and oil) are draining the savings from past CO2 fixation.

　However, before we start gushing about such indirect things, we should face the fact that the thermal efficiency of gasoline internal combustion engines (represented by private automobile) is around 45%, even at the maximum efficiency.
(See  Automobiles dump 60% of the power of gasoline into the atmosphere:本に溺れたい)　

According to UN statistics, in 2010, there were 1 billion cars owned by the world's population of 6.9 billion (1 car for every 6.9 people). In the future, if the spread of personal cars in middle-income countries takes off, the total number of cars owned could reach 2 billion.

　The basic concept of technology, in which heat is first generated and then converted into motion, has remained basically unchanged for 200 years since the improvement of the steam engine by Watt. Even the highest thermal efficiency of a standard passenger car in Japan, which stands at the forefront of this technology, is about 45%, and of the heat generated by burning 1 liter (1000 cc) of gasoline, 550 cc worth of heat is directly discharged into the atmosphere in the 21st century. In the face of this fact, I am surprised that the main culprit in global warming is not the use of internal combustion engines by mankind. And this problem cannot be overcome by technological illusions. This can be seen in the results of recent studies, which show that even in plant photosynthesis, the efficiency of solar energy use is in the 40% range.

　It is a natural law that living on the earth inevitably dissipates energy and heat. If you claim that this can be overcome by the wisdom of mankind through "technology" and "innovation," you are nothing more than a "cult" that believes in "perpetual motion," "magic," and the "arrival of singularity.