I was pleased to read this article, which states that the number of trees on Earth could be as high as three trillion:
The article notes that this is a vastly higher estimate than the previously-thought figure of 400 billion trees, although it also notes the the actual number of them could be "...anything between the two [numbers] - or even 10 times higher."
This does not mean, however, that deforestation is not a problem. The article also states that fifteen billion trees are removed annually while only five billion are planted to replace them. On the bright side, this does mean that significantly less than 1% of trees globally are cut down each year and there are efforts to plant to more trees to offset those that humans use.