Everyone knows that humans — indeed almost all animals — breathe oxygen (O2) and therefore absolutely depend on this molecule for their survival. However, we often forget where this oxygen comes from… and that is plants.
You may not know that during the first half of the Earth’s history (it is estimated to be about 4.5 billion years old), its atmosphere contained almost no oxygen: less than 1%. However, with the evolution and expansion of cyanobacteria (blue-green algae, precursors of plants), then of plants themselves, that changed. Both of them absorb, use and sequester carbon dioxide (CO2) during photosynthesis while rejecting oxygen as a waste product and this has gradually, starting about 2.3 billion years ago, increased the planet’s oxygen level to today’s level: about 21%.
I think it is worth remembering that it is thanks to plants that we can breathe.
The Amazon forest, heavily threatened by human exploitation, produces 20% of the oxygen released on Earth each year. The phytoplankton in the oceans that we pollute so heavily produce even more. Each forest chopped down and each parking lot paved reduces oxygen levels in the air and yes, they are declining worldwide, especially in our cities (it can be as low as 12-17% in major cities, easily enough to cause its citizens respiratory distress).
Everything we do to “green up” our environment — cultivate a garden, grow plants on the deck, let climbing plants cover the walls of our houses, grow houseplants, etc. — is good for both our health and our environment… and also for the planet.
In short, we humans owe our survival to plants. Maybe they deserve a little respect!