All those verbs are very aggressive, suggesting forceful and intentional action. I would instead use the word "whittle." This suggests taking off a small piece at a time in a casual way. Whittling is often a pastime of idlers like this fellow -- perhaps he both whistles and whittles.
However, this word might not be strong enough if you are also trying to convey your own strong distaste for what the man is doing, or to imply that he is neglectfully destroying something precious. In that case, consider "butcher." Maybe even "dismember" (which would suggest that the land is a living thing being cut apart).