Social science becomes a major component of ecological research at Harvard Forest.

Jennifer Weeks

Forests are complex ecosystems, so it’s not surprising that the interests of researchers at Harvard’s ecological research site, Harvard Forest, located about an hour west of Boston, range from ecology to atmospheric chemistry and plant physiology.

While researchers have traditionally focused on the natural drivers of forest change, such as pathogen populations, in tightly controlled research plots, they are now working with social scientists to understand the human element behind forest ecosystem change. “You’ve got to understand what motivates people who own land and the constraints on their behavior,” says Harvard Forest director David Foster, who is also a senior lecturer in biology at Harvard. “Forest change is bigger and more complex than just what happens on research plots.”

For example, subjecting a piece of land to logging, farming, or dividing it for different uses influences how it will respond to stresses like invasive plants, hurricanes, or climate change. Getting a better handle on how humans have affected forest change in the past may enable researchers to better predict the future effects of human activity, such as conservation practices, farming, or the use of forests as “carbon sinks” to lower greenhouse gas levels and combat climate change.

Forest as lab

Since 1988, the 3,000-acre Harvard Forest, in Petersham, MA, has been one of 26 sites around the world that make up the U.S. Long Term Ecological Research network funded by the National Science Foundation (NSF). Today, research projects range from studying the spread of invasive plants and insects to the influence of elevated carbon dioxide levels on forest growth.

A $4.9 million NSF grant awarded last year is allowing Harvard Forest researchers to work more closely with environmental historians, anthropologists, and public policy experts. They look at issues such as private landowners’ attitudes toward their land by conducting opinion surveys. They also study the history of farming and forestry in New England through old land records and policies regulating logging rates.

“The forest has a legacy of prior land use, and we need to understand it,” says Harvard atmospheric scientist Steven Wofsy, who studies fluxes of key gases between the atmosphere and biosphere. “We listen avidly when people talk about forest history.”

Wofsy’s group has been looking at the factors that affect how much carbon a forest can pull out of the atmosphere. They’ve found that seasonal factors such as length of growing season, snow cover, cloud cover, and drought are important regulators of forest carbon uptake from year to year. But over decades, they say, prior land use is the dominant factor.

The human factor

For example, the Harvard Forest site was farmed until the 19th century; by the 1930s, the area was populated with white pines, which are often found on previously farmed land. Those trees were easily blown over when a hurricane came through in 1938. After the storm, red maples and other large hardwoods, which take in significant amounts of carbon, became established. So historical activities on the Harvard Forest site—farming, along with the hurricane—are a major factor in its carbon uptake rates today, Wofsy says.

Such findings help to explain why forests in the northeastern United States can sequester larger amounts of carbon than other forests in the country. They also suggest that forests’ carbon sequestration rates can be maximized over the long term by planting the right species and regulating logging rates.

This interdisciplinary approach to forest research also advances conservation. In 2005, Foster and eight colleagues from the natural and social sciences published Wildlands and Woodlands, a report that outlines an aggressive forest conservation strategy for Massachusetts. Advocates are working to advance the strategy, which calls for protecting an area half the size of Massachusetts from development.