[user104658]

Well. To be controversial ... what IS a little reported scientific fact, is that grass creates more oxygen than the same area of trees. It's not exact, but it's often (falsely) reported that if an area of the Amazon is deforested then the world loses that area of oxygen creation / CO2 removal. If the area is replaced by grass - e.g. cattle grazing - then that's just not necessarily the case.

There ARE a whole host of things we lose when areas of the Amazon are destroyed of course but the "we need the oxygen" argument is over-played and inaccurate.