Of course not, but they do reproduce and can do quite fast for animal propagated tree species. We are talking about 3.04 trillion trees. Even if the natural germination rates are low, it would still be significant enough to make a difference in the assertion this article uses as introduction.
Like I said, a lot of things have to be taken into account, including local deforestation and its effect on desertification. Higher averages temperatures are forcing forests to move to higher latitudes, but they are also clearing areas of growth that are not yet inhabited by humans and were far too cold before for trees to propagate to.
I'm not suggesting that there's not a problem with the way we use our forest resources, just that the oversimplification of the starting premise of the article doesn't help at all.