Forest decline in the eastern U.S.?

Covering much of central New York State is a mosaic of forest, pasture, and cornfields punctuated by lakes, small towns, rural residences, and sometimes wind turbines (© Peter Klepeis)

by Peter Klepeis

Most news coverage of forests tends to focus on deforestation. And for good reason. The Food and Agricultural Organization concludes that from 2000-2010 upwards of 13 million ha of forest per year were converted to other uses or lost to natural causes. Most of the clearing occurs in the tropics, and the resultant biodiversity loss, carbon dioxide emissions, and threats to local inhabitants are among the reasons to be concerned.

Global trends in forest cover hide regional differences, however. Many temperate and rich-country contexts have been experiencing forest recovery for decades. In the eastern United States, for example, cleared areas reached their peak in the mid-to-late 19^th century, but this was followed by widespread natural forest regeneration. This forest expansion is celebrated for increasing carbon sequestration and improving water quality, reducing flood risk, decreasing soil erosion, expanding wildlife habitat, and providing opportunities for recreation and extractive industries. But it is not entirely positive. As described in Jim Sterba’s new book Nature Wars, extensive forest cover, a decline in hunters, and a lack of natural predators has led to a boom in wildlife – and deer in particular – with tick-bearing disease, auto accidents, and munched veggie gardens among the negative consequences.

Regardless of its positive or negative impacts on nature and society, what explains the shift from net forest loss to net gain? In the early 1990s the geographer Alexander Mather started to develop forest transition theory: economic development, the abandonment of lands marginal to agriculture, and the movement of rural inhabitants to urban areas tend to stimulate forest recovery. The theory captures fairly well the recovery trends seen in the U.S. and Europe over the past few hundred years. But the theory is not without its critics. Forest change is dynamic, non-linear, and the factors involved are linked to specific places and time periods. Not surprisingly, therefore, recent scholarship documents how – after decades of net gain – forest cover in the eastern U.S. started to decline in the 1970s.

In a new article in the journal Area, my co-authors and I use aerial photographs to evaluate changing forest cover between 1936 and 2008 for a town in central New York State. As expected, a decline in the farming sector and changing life and livelihood goals within farming families led to 25.8 % of the town reforesting. Two new trends emerge, however. First, there is a pronounced increase in the percentage of forest recovering on prime agricultural soils, which holds the potential to diversify habitat and increase biodiversity. Prior to 1994, reforestation on high quality soils was rare. Second, alternative land uses and invasive species, such as the Emerald Ash Borer (Agrilus planipennis), represent possible new forms of forest disturbance. Landowners are starting to develop wind power and natural gas, and practice silviculture. Also, there is steady growth in amenity-oriented land use and rural residential development. These new dynamics challenge theories of forest change, and raise questions about the prospects of sustainable land and forest use in the region.

The author: Peter Klepeis is Associate Professor of Geography at Colgate University, N.Y., U.S.