The proponent is a chap named Steve Taylor who by all accounts has the background to equip him to know whereof he speaks. I can't find his work in print so far, but here is a promising summary:
According to Steve Taylor, Plainfield farmer and retired New Hampshire Commissioner of Agriculture, the only period of agricultural prosperity in the state, albeit a “flash in the pan,” occurred with the institution of sheep farming in the 19th century. Forests were “stubbed,” a process of girdling, burning and clearing away trees; 250,000 miles of stone walls were constructed (100,000 miles remain today); 1,500 Marino sheep were imported from Spain and bred until they outnumbered the human population; woolen mills popped up in nearly every village; and the sheep farmers thrived building large country estates supported by a strong demand of wool products.And here I thought those stone walls went back to the 18th Century, or even the 17th. In my youth, they were great for berry picking. I should think the berries also have faded, the victim in this case of the second growth timber. I assume the population of rattlesnakes, still a novelty in my youth, continues to grow.
The construction of the Erie Canal and the development of railroads (opening the European market to the Midwest), competition from Australia and Argentina, and the Industrial Revolution (workers worked indoors warmed by box stoves instead of heavy wool coats), all contributed to the equally rapid decline of the sheep farmers prosperity.
It’s been more than 150 years since the sheep boom and now the forest fills 85% of the New Hampshire landscape, which was once pastureland, and only 5% in open farmland remains. Taylor is fighting to retain the small niche that farmland holds today.