Sorry, I don't see any contradictions.
"We know that climate change is causing a shift if vegetation. You need only look at how growing charts have changed to see this. There are already changes in arctic vegetation, the paper shows comparative photos of this. The paper projects this forward and shows how vegetation increases lead to lower albedo, and even more warming."
"By incorporating observed relationships between plants and albedo, we show that vegetation distribution shifts will result in an overall positive feedback to climate that is likely to cause greater warming than has previously been predicted,"
The second statement comes from the paper's authors.