Fine.
While we may be losing the Brazilian rainforest, there are far more trees being planted than there are being cut down. While Sceral, earlier, cited the fact that the US has only 6% of its old forests, that's actually a good thing. Due to various environmentalist measures put in place throughout North America and Europe, there are now five trees being planted yearly for every 1st Worlder alive in the 1st World. This means that 6,905,602,940 trees are being planted yearly in the 1st World, and 575,466,911 are being planted monthly (working out to approximately 19,182,231 daily).
Now, this begs the question, how many trees are cut down yearly? According to Genentech, around 102,234,930 (we have statistics on everything). This is the whole world's logging industry, just to get that through. This means that the world has a net gain of 6,803,368,010 trees per year, which means we really don't need to worry about the logging industry. But that doesn't really answer the issue, does it? Newer trees exude more oxygen and take in more carbon dioxide than older trees--the same thing happens with humans, only vice versa. Ever notice how breathing seems to get harder for older people? There's a reason for that, and that reason is merely that their equipment is getting old. As a person gets older, more oxygen is simply wasted via various routes rather than pumped directly into the heart and thus into the blood.
The same thing happens to trees. With the Amazon being one of the oldest forests in the world, the carbon-dioxide-to-oxygen-conversion efficiency rate of the average tree is somewhere around 20% of a sapling. The Amazon, further, is a unique environment, where the (very) long-lived trees hardly ever die, and new trees hardly ever grow, mostly due to the very bad quality of the soil and the lack of cleansing forest fires to burn out the aging deadwood. Now, you're right, it would be a bad thing if the Amazon were cut down--if there were no trees being planted anywhere in the world. But as I've shown, there certainly are, and those six billion trees are young and far more efficient than your average Amazon tree, and thus provide far more oxygen. Thus, cutting down the Amazon would not hurt our oxygen supply: in fact, it would improve it because of the various oxygen-providing plants that will be planted in its remains.
That said, it will still be a terrible loss to biology and it hurts me deeply. But it's Brazil's forest.
EDIT: Man, there were a lot of posts while I was writing this.
