The biggest cause of the recent fires in the Amazon are due to deforestation. It is one of the leading causes of destruction of forests and jungles on our planet.
The best way to help is by looking at what you are buying and checking if that is harmful to the nature that surrounds us or not. Palm oil is a common substance used in every day items, like soap, make-up, toothpaste, wax and many other things. These are the trees which are being planted after deforestaion of the Amazon. It is due to this that many species are losing their home. When fires happen, it's not just the oxygen that is being lost but also the animals' lives and habitat.