Looking at Four Centuries of Change in Northeast Forests

A Harvard-Smithsonian study released on September 5th in PLOS ONE compared modern forests to their pre-colonial condition.  The purpose of the study was to answer the fundamental question: How similar are today's forests to those existing prior to European colonization?  What they found might surprise you. 

Researchers looked across a 9 state region from Pennsylvania to Maine comparing more than 300,000 witness tree records and compared them to modern US Forest Service data.  The northeastern United States is a predominately forested region (80% forested) that has undergone a 400-year history of intense logging, land clearing for agriculture, land abandonment, and natural reforestation. During the 18th and 19th centuries more than half the forestland was cleared for agriculture and cut for timber. Most farms were eventually abandoned, and during the 20th century, forests returned. 

A view of the Swift River Valley in Central Massachusetts,
 photographed in 1890. The image shows extensive forest
 clearing for agriculture.
Photo courtesy of the Harvard Forest Archive.

The same view photographed today. Forests have made
 a similar recovery in many parts of the Northeastern U.S.
Photo by David Foster.

Below are a number of key findings:
1. Looking only at a tree species list Northeast forests haven't changed.
2. Maples have exploded across the Northeast, increasing by more than 20%.
3. Beeches, oaks, and chestnuts have declined sharply.  This is of concern for wildlife depending on nuts for winter survival.
4. Pine numbers have shifted more than any other tree type, increasing in some places, decreasing elsewhere.
5. Colonial farming history was found to be the most powerful factor in determining modern forest composition -- more powerful than regional climate, soil conditions, and numerous other factors.
6. Todays forests are more homogenous and less responsive to small changes in temperature and precipitation.

David Foster, a co-author on the study, indicated that despite the impacts of disturbances such as forest clearing, widespread logging, fires, climate change, invasive pests, and disease, the Northeast remains the most heavily forested region of the country.  Foster also notes, "If we do not replace forests with houses and pavement, they will endure future challenges as well."

Click here to read the news release, browse photos, download the full scientific paper, and more.