Did u know that one tree can provide enough oxygen for 2 people to live off of for their whole lives ? Well, The earth’s atmosphere has a different composition & the trees and plankton play a big role in this. A mature leafy tree produces as much oxygen in a season as 10 people inhale in a year. The trees release oxygen when they use energy from sunlight to make glucose from carbon dioxide and water & a human breathes about 9.5 tonnes of air in a year, but oxygen only makes up about 23 percent of that air. The relative molecular weights of oxygen and carbon, which equalize to 100 kg of oxygen per tree per year.