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Effects of human impact are long lasting for forests in Northeast U.S.

Grow fast, die young is not a lifestyle normally associated with trees. But in the forests of the Northeastern United States the red maple follows such a life strategy. It is among the first trees to seed and sprout in open fields and through rapid growth quickly dominates open areas. In the Northeast red maple has been a big winner in terms of population growth in the 150 years since people began abandoning their farms in the Northeast and moving to cities. Researchers estimate that the population of red and other maple trees has increased by some 20 percent in the last four centuries.

“In the presence of forest fragmentation and human impact red maple has done really well” explains Jonathan Thompson, a research ecologist at the Smithsonian Conservation Biology Institute in Front Royal, and co-author of a new paper in the journal Plos One describing four centuries of change in the forests of the Northeastern United States.

The historical dioramas in the Harvard Forest Fisher Museum tell the story of the region's forest loss and regrowth. (Photo courtesy of the Harvard Forest)

The historical dioramas in the Harvard Forest Fisher Museum tell the story of the region’s forest loss and regrowth. (Photo courtesy of the Harvard Forest)

But too many maples is not a good thing, Thompson explains. “Red Maple isn’t a very desirable tree: it lives less than 250 years, doesn’t produce hard mast such as acorns that animals can eat, it doesn’t have any timber value and it doesn’t provide good cavity nesting for woodpeckers and other birds and animals.”

The good news is that most of the Northeast’s native tree species remain and that the region has reforested much of the area that had been originally farmed. However, red maple’s rise is an example of how forests of the Northeast have been transformed by humans. Indeed, the abundance and distribution of most tree species has shifted dramatically, favoring early- and mid- successional trees like the red maple.

Huge oak, hemlock and beech filled the mature forests that greeted the first colonists. But because these trees are slower growing, long-lived, and slow to recolonize after a disturbance they have suffered steep declines in their numbers overall through clearing, land use and logging. Getting the forest back to its original mature state would require centuries of undisturbed recovery, and that’s not likely to happen. Even if the forest disturbance caused by humans ended today, the Northeast may never again see mature forests such as those that existed when the colonists arrived, Thompson points out.

“If everything was the same climatically and atmospherically as it was hundreds of years ago, it would take centuries for the forest succession to progress along the same trajectory it did previously,” Thompson explains. “But today there’s more carbon dioxide in the atmosphere, the climate is warmer, there’s much more nitrogen in the water and soil; the hemlock wooly adelgid [an invasive insect] has killed virtually all the hemlocks south of Connecticut and is marching north; there’s a beech bark disease that killing beech trees,”  Thompson says. “What’s more, a different type of deforestation is taking place today. It’s not agriculture and forestry, but residential development and urbanization. So, who can say what impact these new factors will have on the recovery of our forests.”

Forest cover was increasing in the Northeast until about a decade ago, Thompson points out. “But now the trend has turned downward again and we have this sort of second chance where we get to decide about the future of the forest in New England and whether we are going to march back down towards the deforested state. I don’t think we will get this opportunity again.”

John Barrat




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