If you wanted to learn what the local forest was like before Europeans arrived in the eighteenth century, what would you do? One obvious approach would be to visit the few remaining bits of old growth forests in the region and draw your conclusions from what you see there today. Those remnant forests, however, would give you a picture that wouldn’t be particularly accurate, says plant ecologist Charlie Cogbill.
“We have patches that have survived for a long time, but almost to the one, they survived for very straightforward but significant reasons: they weren’t logged, they weren’t sought for clearance of land, they weren’t agricultural, they couldn’t be gotten to. The remnant stands are the oddballs, they are the extremes,” said Cogbill in a recent interview.
Rather than the oddball, Cogbill has spent a large part of his career studying the typical pre-settlement forest. Piecing together a forest that no longer exists is the work of a detective, and Cogbill’s detective work began in the 1970s while he was completing a master’s degree at Hubbard Brook Experimental Forest in Woodstock, New Hampshire, studying forest dynamics. As he tried to better understand the ways in which human activity has changed our forests, he began his archival search for baseline information on the forest that was here before it was cleared for agriculture.
The documents that have proved most revealing to Cogbill are “lotting” surveys, the surveys by which the proprietors of a new town divided the town into lots for the earliest settlers. At each lot corner, the surveyors tended to place a monument, often a post or stake or a pile of stones. They also routinely made mention of a nearby “witness tree.”
Cogbill compiles data on every tree mentioned in the surveys and then calculates the relative abundance of the tree species in each town. Fighting through naming nuances and regionalisms - for instance, black gum is called pepperidge in Connecticut, swampwood in Massachusetts, beetle wood in Vermont, and wild pear in New Hampshire - he has been able to paint a detailed and localized picture of what the forests of Vermont and New Hampshire looked like centuries ago.
That forest was quite different from today’s. “There’s been a monumental shift in the amount of beech from pre-settlement days, when there was a huge amount of beech everywhere. In northern New England, it was 40 percent of the original forest throughout almost the entire area. Today, according to FIA (forest inventory and analysis, done by the USDA Forest Service) figures, it’s more like 15 percent,” Cogbill said.
Whether one specific area of beech was replaced by maple forest is not so easily seen, but the overall shift is clear, and the loss of beech is not a result of beech bark disease, which began in the last century, long after its decline had begun.
Spruce is another species that was once more common. “Spruce has declined significantly, not just in the spruce zone of the high mountains but in the mixed woods on the uplands,” said Cogbill. “It was a major representative in the mixed woods in southwest New Hampshire and the Piedmont of Vermont, but coming out of the 1800s, spruce was removed as a player from the mixed forest. The forest we now see at Hubbard Brook, which was mostly spruce mixed with northern hardwoods, is now northern hardwoods. It’s gone from our minds that that used to be where spruce was. That’s not acid deposition. That happened before acid deposition. That was land use.” Cogbill cited work by a Forest Service silviculturist named Westveld, who showed that when spruce was logged out of the mixed woods, it didn’t come back.
Surprisingly, white pine’s reversal has been in the other direction, toward plenty. “Pine is a tree that has a huge reputation for being abundant, but it simply wasn’t a major tree on the uplands in northern New England. It shows up less than one percent regionally. It was very uncommon.
“There were areas along the rivers that had very merchantable pine that was harvested early on. Otherwise, in the uplands, they didn’t have very much, or had a scattered tree here or there. The witness tree surveys show that pine was very localized in the major southern valleys.”
Knowing what species made up the pre-settlement forest, however, doesn’t suggest to Cogbill that we should be trying to re-create that forest. “That’s unreachable. We really have gone through a bottleneck of land use, and it’s not just recently. The major blow in northern New England was the original land clearance. We changed the soils, almost permanently. They’re still productive, they’re still soil, they haven’t been paved over, but the natural progression has been disrupted. We’re on a trajectory, and you can’t force it back.”