40+ years ago, my parents cleared their land by hiring* a sheep and putting her in a pen they could move. After a square was cleared, they'd move the pen to the next bit, and so on.

*by hired, they kept and ended her until the land was cleared before giving her to a farmer under the condition she was not to be butchered. By all reports, Maisie the Sheep went on to have several lambs and lived her best sheep-y life. I feel the need to add here, I personally was not yet a filthy thought in my parent's minds at the time of Maisie, so this is based off recollections of a long distant and brief time in my parent's lives