September 5, 2013
Northeastern Forests Much Different Than 400 Years Ago Due To Human Activity
Brett Smith for redOrbit.com - Your Universe Online
From climate change, to disease, to human activities – a lot has happened to the forests of New England since the years leading up to the Pilgrims’ arrival in 1620.A new report published in the open access journal PLoS ONE tracked the changes to these woodlands that have occurred over the past 400 years and found significant differences between now and pre-colonial times.
"The modern forest is compositionally distinct from the pre-colonial condition," the scientists from the University of Wisconsin-Madison, Harvard University and the Smithsonian Institute wrote in their report.
In the study, the scientists compared the composition of the modern Northeastern forest across nine states, from Maine to Pennsylvania. Using land-survey records that included 300,000 references to individual trees during pre-colonial times, the team discovered that the species and variety of trees were mostly the same as they are today. However, the distribution and numbers of these trees have changed significantly since the early 1600s.
"If you only looked at a list of tree species, you'd have the impression that Northeast forests haven't changed. But once you start mapping the trees and counting them up, a very different picture emerges,” said Jonathan Thompson, from the Smithsonian Institute.
Beech, oak, hemlock and spruce trees were found to be are less abundant. Beech had the most dramatic decrease in population in areas of Vermont, western Massachusetts, and northern Pennsylvania. In pre-colonial times, beech made up an average of 22 percent of forest trees, compared to about 7 percent of forest trees today. However, fir, cherry and maple trees became more abundant, with maples jumping from 11 percent of forest composition in the past to 31 percent in modern forests.
The researchers noted that most of that change is due to two hundred years of logging and agricultural clearing that started around 1650. After the cessation of these activities, the cleared areas were eventually reclaimed by the forests as trees moved back in. They also noted that one tree in particular actually benefited from human activity.
“The 400-year history of land use benefited maple the most and it is now a dominant taxon throughout most of the region,” the authors wrote.
The team also discovered that modern forests have a more consistent composition that isn't as affected by precipitation, temperature, elevation and other factors. The researchers said the forest composition between "any two towns, on average, is slightly more similar in the modern era than it was in the colonial period” regardless of distance.
“The northeast is once again a predominantly forested landscape, but today's forest is not a facsimile of its predecessor,” the authors concluded. “We find this to be at once disheartening and encouraging. On the one hand, the modern expense of forest is diminished in so many of the components and processes that once characterized the regional ecosystem; on the other, given the extent and magnitude of land use it is remarkable that native species predominate and the forests looks in many ways as it has for millennia.”
Image Below: (LEFT) Human activity has transformed Northeastern US forests over 400 years. This photo shows the forest cover in Slab City in 1890. Credit: Harvard Forest Archives, Photographer unknown. (RIGHT) Human activity has transformed Northeastern US forests over 400 years. This photo shows the forest cover in Slab City in 2010. Credit: David R. Foster