Stop lighting fires and reduce the number of animals alive..
you can reduce it by stuff
Reduce
oxygen
A rainforest can reduce carbon-dioxide and produce oxygen by absorbing carbon-dioxide and releasing oxygen through photosynthesis.
An increase in the amount of organic matter in an aquatic system will reduce oxygen levels because if more organic matter is introduced the population of decomposing bacteria will increase and they will use up more oxygen for respiration (by which they decompose matter) than that which is being produced, thereby reducing oxygen levels.
Because emphysema reduce the oxygen perfusion (transfer) from alveoli into the blood thus also reduce the oxygen supply to the muscle and organ. Reduce the oxygen delivery to the periphery cause weight loss and thus they (emphysema patient) look thin.
Hydrogen Peroxide H2O2 and Superoxide O2-
the tar like substance prevents your lungs from taking in enough oxygen.
Cellular respiration uses oxygen and generates carbon dioxide. Photosynthesis uses carbon dioxide and generates oxygen.
We can reduce the use of limestine by
Bromine can be reduced quite easily by use of all element that react with it, except Oxygen, Fluorine, Chlorine and some other strong Oxidizers
Smoking can weaken the lungs and reduce breathing capacity. Also smoking can reduce oxygen level of blood thus blood can not carry enough oxygen to the necessary organ.