Understanding photosynthesis, trees, and conservation of mass.

[u/Maleficent-AE21]

[u/cheeseybees]

I thought (maybe i'm wrong?) that they still respire... so taking in Oxygen, and breathe out CO2... and that photosynthesis is a different mechanism that extracts CO2 from the air and produces O2

Pretty sure I read somewhere that some trees can take around a decade to grow to the point where they become net extractors of CO2?

[u/Echo__227 → u/cheeseybees]

Most life generates the energy to life by oxidizing the carbon from organic molecules, including trees.

What's unique about photosynthesis is that they also create new organic molecules (reduced carbon) from CO2 (carbon fixation) from free sunlight.

Biomass relies on having lots of organic molecules available. Whereas animals need to eat organic molecules both for energy and new mass, plants generate their biomass entirely from the CO2 in the air (with the exception of parasitic plants and such). That means any amount of living plant biomass is a net reducer of atmospheric CO2: the sugars it burns to live simply return what was taken from the air, and the rest becomes part of the growth.

However, because plants die and decompose, we have to think about, "How much CO2 is in plant or other photosynthetic organism biomass at any one time?" That's where calculating total carbon sequestration is important because it conversely means "How much less carbon is in the air at any one time?" Forests are a great way to sequester carbon because trees are massive and long-lived. All coal in the world represents carbon sequestered in the Carboniferous period that was then buried for a long time. However, by far the greatest carbon sequestration is in oceanic algae and the processes that cause dead algae to be buried on the ocean floor (where all the oil in the world came from). This is what ecological scientists such as marine biologists dedicate a lot of effort to researching: how we can prevent disrupting the protective carbon sequestration of the natural world.