In the woods of New England, a stone wall may be the remains of a farm. The trees on either side can be younger than the boundary between them. At Harvard Forest, museum displays follow the change: fields enclosed by walls, young pines spreading across abandoned pasture, and woods growing around the old divisions.
The walls took a great deal of work. Farmers cleared stones from the ground and used them to mark boundaries and contain livestock. The open country around them also required work, repeated every year. A pasture stayed open because animals grazed it. A field stayed a field because someone continued to cultivate it.
Across much of New England, that work began to stop in the middle of the nineteenth century. Railroads brought cheaper western crops into eastern markets. Factories offered wages to people whose families had worked the thinner, stonier soils. Farming continued, but many of the less productive fields were left. White pine spread into abandoned pasture. In time, trees concealed the shape of the farms.
The railroad had an unusual part in this. Its construction consumed timber, and its trains carried farm goods that made some eastern farmland less profitable to cultivate. The same network helped clear land in one place and helped end cultivation in another. A railway map alone would not show both effects.
There was another change beneath the rails. Wooden ties decayed and had to be replaced. Preservative treatment extended their useful lives, and improving that treatment became an early task of the Forest Products Laboratory in Wisconsin. Keeping a tie in service longer meant fewer replacements for the same stretch of track.
Fuel changed too. Coal took over work once done by firewood in homes and industry. That eased one demand on forests, even while population growth and other uses kept total demand for wood rising. The substitution came with damage of its own, in mines, smoke and the atmosphere. A reduction in pressure on one resource could move the burden somewhere else.
The Forest Service's 1993 film, America's Forests: A History of Resiliency and Recovery, follows these changes alongside the familiar conservation story. Public forests, planting and protection mattered. So did ordinary decisions about what to burn, where to farm, and how often a piece of wood needed replacing. Much of the work that allowed trees to return happened away from the forest.
As agriculture became more productive, more food could be grown on land already being farmed. Tractors also reduced the acreage needed to feed horses and mules. Nationally, the long expansion of cropland slowed and then stopped in the early twentieth century. Some regions continued to lose forests while others regained them. The balance changed through many decisions made for reasons that had little to do with trees.
None of this made a new forest identical to the one that had been cleared. An acre counted as forest says little about the ages of its trees, its habitat or the effects of its former use. New England's second-growth woods still carry the history of farming in their soils and vegetation. The return of tree cover was substantial; the ecological history was more complicated.
Those woods are easy to mistake for land that escaped human use. The wall offers another explanation. People put an enormous amount of effort into keeping this ground open. As work moved elsewhere and farming became less profitable, many fields could grow back. The stones remain where they were laid, under trees that came later.