Trees once covered almost the entire eastern seaboard of the U.S. Vast forests supported a rich ecosystem, including flocks of the extinct passenger pigeon big enough to blot out the sun. But by the 1920s at least half of this forest was gone—a victim of tree-clearing for farming, forestry or fossil-fuel extraction.

Then, the forest rebounded for several decades as once-farmed fields were left fallow. But a new study reveals that since the 1970s eastern forests have begun to diminish again; roughly 3.7 million hectares of forested land—an area larger than the state of Maryland—have been transformed into subdivisions, tree plantations and lunar-esque landscapes resulting from mountaintop removal mining. In fact, the latter activity alone eliminated 420,000 hectares of woodlands in the past two decades.

"Human land use is a primary driver of environmental change," says geographer Mark Drummond of the U.S. Geological Survey (USGS), who collaborated on the study in the April issue of BioScience with USGS Earth observation scientist Thomas Loveland. "The cumulative footprint of human activities on the land surface is causing a significant net decline in forest cover."

Suburban sprawl was the leading cause of the forest's recent retreat in much of the east. The megalopolis that stretches from Boston to Washington, D.C., has grown in extent by 90 percent since 1970, resulting in the cutting of 1.9 million hectares of trees. The southern coastal plain, northeastern highland and the Piedmont—the hilly region between the coastal plains and the Appalachian Mountains stretching from New Jersey into Georgia and Alabama—lost the most forest cover.

That's bad news for the wildlife that had rebounded along with the woods. It also means that the newly lost trees are not incorporating more carbon dioxide—the most common greenhouse gas changing the climate. Since the early 20th century U.S. forests had been soaking up extra CO2, and this timberland was expected to play a role as an "offset" for greenhouse gas emissions from other sources (like the coal-fired power plants burning through the products of mountaintop removal mining) in any legislation to combat climate change, such as the bill currently being written in the U.S. Senate. "Over the past 30 years, the strength of the carbon sink may have decreased by as much as two thirds in some eco-regions of the east," the USGS researchers wrote.

"We need to improve our understanding of how the U.S. landscape is changing as a result of human activities," Drummond says. "The amount of decline in carbon sequestration is still being examined."

The USGS scientists used Landsat satellite data since 1972, combined with field visits, to more precisely estimate forest cover in the 162 million hectares of the eastern U.S. Previous efforts from the Food and Agriculture Organization of the United Nations (FAO) and U.S. Department of Agriculture had found that forested areas in the eastern U.S. were still expanding overall, if only marginally, based on estimates.

Nor is this trend confined to the eastern U.S. Whereas FAO figures note that deforestation may be slowing globally—from 16 million hectares a year in the 1990s to 13 million hectares per year in the 2000s—that trend may have stopped or reversed in the developed world. "The recent declines in eastern forest cover that we are seeing may herald similar trends elsewhere, in other regions or nations," Drummond says. "We see net forest declines in the west and areas of the south-central U.S. caused by land-use change."

7 Comments

1. 1. bertwindon 01:10 AM 4/14/10

   Shrinking woodland is the reality - along with "windfarms" and other great business enterprises - fluffy dice, etc., for the windshield - and now parochial, tiny-minded TV channels telling us what a good deal it all is ? The trouble is that they may genuinely believe it. Very wierd religions exist - a fact - and who cares how wierd others think I am so long as I can stay in my dream-world.

   Reply | Report Abuse | Link to this

2. 2. jtdwyer 03:04 AM 4/14/10

   Yes, I suspect there is a strong statistical relationship between the human population and human land use, human fossil fuel combustion, human protean consumption, human ...whatever!
   
   It shouldn't take a rocket scientist to figure this out: humanity's impact on the Earth's environment and all other living creatures is directly influenced by our increasing population.
   
   It's great that scientists are being encouraged to publish studies concerning the indirect results of population growth, but isn't it about time scientists determined we can best reduce the human population while minimizing the suffering of those already living and maintaining their personal liberties as much as possible?
   
   Is it too much to ask that scientific methods be applied to solving the problems overpopulation produces rather than continuing to precisely categorize and quantify them? Population reduction is our only effective choice for survival. Continuing to enable unsustainable population growth does not enhance long term survivability.

   Reply | Report Abuse | Link to this

3. 3. kilingtonskier 10:05 AM 4/14/10

   Forests are not in decline in Vermont, New Hampshire or Maine. In the past 30 years, beautiful hill side pastures have gone to the trees.

   Reply | Report Abuse | Link to this

4. 4. jtdwyer in reply to kilingtonskier 01:44 PM 4/14/10

   kilingtonskier - Interesting conflict, although the report was produced by real scientists (tic). I presume your assessment is based primarily on mountaintop observation?
   
   The 'Bioscience' reference is a paper written by a couple of USGS researchers based on "...using remotely sensed imagery as well as statistical data, field notes, and ground photographs." It's unclear what level of expertise the USGS team has in the field of remote imagining analysis. Again, these were real scientists, but perhaps some assistance from experienced military image interpreters and analysts would have been beneficial. Occasionally even real scientists dispute the findings of other real scientists...

   Reply | Report Abuse | Link to this

5. 5. abyssalmystery 07:53 PM 4/14/10

   I have two comments:
   
   1. Suburban sprawl is an evil as bad as population growth. Both need to be curbed.
   2. On the other side of the equation we must not forget that suburbs are not parking lots. Most established suburbs are heavily wooded and would be more so if we encouraged people to minimize lawns in favor of shrubs, etc.

   Reply | Report Abuse | Link to this

6. 6. doug l 10:27 AM 4/16/10

   Decline from what? From which natural state are we presuming the forest is degrading? The state in which the forest was before modern humans came to America approximately 10 thousand years ago? Or the state in which the forest existed when millions of pre-industial native americans had lived in the eastern woodlands and during which over dozens of centuries had managed to cultivate the forest with practices such as buring, selective harvesting and replanting so that instead of a natural balance and distribution there were a far higher number of nut and fruit trees and far fewer wild animals? Or the forest that the first modern europeans to enter and reported that they'd found in the early 17th through 18th century, a wild tangle of undergrowth and proliferation of huge numbers of animals and birds now that the native americans were no longer there to constrain growth in numbers by harvesting the wild bounty, more than a hundred years after the original inhabitatants had essentially disappeared due to contact with european introduced diseases? Which forest are we talking about? Take a good look at any old photo of what now look like mature eastern forests and we see that the forests are coming back as small settlements and landholdings in the forested areas being abandonned. In some ways, once one gets away from the major corridors over which we travel at high speeds while staring at the sprawl that has formed along the roadside, the actual wild un-cultivated state of our eastern forests and central plains are returning and increasingly left unattended. It's time to consider the true natural history of the world and recognize the true role that humans have played for thousands of years and put our modern impacts into an objective perspective.
   

   Reply | Report Abuse | Link to this

7. 7. mo98 02:12 PM 4/16/10

   Mature trees are needed alongside younger ones designated for lumber and fuel. Replenishment of forests is not planting after clear cutting. Good forest management demands tagging selected trees in summer and cutting them in winter, when it is also more energy efficient to haul them out on sleds. Urban sprawl is likened to the need to take mortgages in order to tear down and build with no consideration for waste disposal, recycling or public transport. Often the black sheep in families are the ones defending waste and sprawl to compensate for other shortcomings we tend to ignore among ourselves for fear of being responsible without political support.
   

   Reply | Report Abuse | Link to this