Log it or leave it?
Along a line in the New Hampshire woods, two forestry philosophies meet head to head. On one side, ferns and moss coat immense logs lying flat among the trees. Here, saplings and shrubs mingle in a lush understory that ripples with the mounds and pits left behind by trees uprooted six decades earlier. On the other side, 60-year-old trees overtop decaying stumps on a comparatively bare forest floor. Both forests are products of the notorious New England hurricane of 1938.
A study in contrast: The photo on the left shows a portion of Pisgah Forest four years after the 1938 New England Hurricane. The image on the right shows a nearby forest in Petersham, Mass., during a salvage logging operation just after the storm.
Photo courtesy Harvard Forest archives.

The difference results from a decision by managers of the Harvard-owned acreage in Pisgah Forest to let the former old-growth forest repair itself in the wake of the storm. Meanwhile, private landowners and government-funded foresters swept away downed and damaged trees elsewhere, including the adjoining portion of Pisgah. In the end, "it was part of the largest salvage operation in U.S. history. Something like 50 percent of the landscape was subjected to salvage logging," says forest ecologist David Foster.

The scene, as described to The Why Files by Foster, represents a great debate: Should damaged trees be harvested from forests after natural disasters? After a disturbance, it's tempting to think of affected forests as "lost" or "destroyed" says Foster, who is Director of the Harvard Forest near Cambridge, Mass. "The large trees as standing, living, majestic individuals are lost, but they're still part of the system."

The urge to purge
Salvage logging has been routine for centuries, often in the name of conservation.

We can see the appeal. Collecting timber from fire-ravaged hills can offset economic loss and satisfy people who like a clean landscape. And, some say, picking the ground clean of litter helps prevent more fires. (Similar logic exists in recent plans to thin national forests in the name of protecting them. Read about the administration's "Healthy Forest Initiative" here. Critics have some objections.) In accordance with that line of thinking, federal and state plans after floods, hurricanes and fires often invite logging.

It happens on a local scale too. "This is often the attitude of a land owner, a land trust, a town board, or a state agency," Foster notes. When people see a damaged forest, their first sense is often that the value has dropped and the land has been scarred. What they want, Foster says, is to recoup some of that loss.

But before we all howl "timber!" Foster has a warning: Stripping forests of trees, even dead ones, blocks the best rebound around. When left intact, ecosystems will repair themselves after extreme weather.

Responding to a "general U.S. administrative hubris regarding the human ability to restore, improve, or repair nature better than nature," Foster and six colleagues called for policies that protect forests in the wake of disturbances in a recent issue of the journal Science.

The authors cite three incentives to leave the logs alone:

The human activities associated with going into disturbed areas can themselves be damaging. Roads and machinery disrupt wildlife and encourage erosion.

Removing organic material -- namely, dead or damaged trees -- means removing the homes for plants and animals that rebuild forests and other ecosystems, bottom-up style.

Many trees damaged in a disturbance don't die, at least not abruptly. In a windstorm, for example, many trees that get knocked flat die very slowly or stay alive. "They are a very important part of the recovery process," Foster says.

The push comes at a time of controversy over U.S. Forest Plans to harvest 29,000 acres of timber in Oregon's Siskiyou National Forest, a region consumed by wildfires in 2002. Critics of the plan, reportedly including the authors of a new EPA review, say logging the area would trigger erosion and watershed pollution.

The critics are probably right, Foster says, in light of history:

Salvage logging after the 1938 New England hurricane disturbed rivers and streams. It also left the soil more vulnerable to occasional fires in the decades since. Soil in logged areas loses more nutrients and suffers more erosion than soil in the regions left intact after the storm.

In Australia's Victoria province, logging of fire-damaged forest in 2002 left cavity- nesting mammals -- like the highly endangered Leadbetter's possum -- without homes.

In 1997 and 1998, after an El Niño-induced drought, Southeast Asia was ravaged by wildfires. In Indonesia alone, more than ten million hectares (about 4,660 square miles) of forest burned. The unbridled logging that followed has hindered, or entirely prevented, forest regrowth.

Harvard's hurricane factory
Foster's own research supports the same thesis. He and a group of graduate students once tackled a stand of trees in the Harvard Forest in the name of science, not commerce. Using winches and other machinery, the group pulled the trees down -- uprooting some, leaving others in the ground -- to mimic a hurricane's effects. In an adjacent spot, the group performed a mock salvage harvest. The rest was left to self-medicate.

"It was quite a surprise," Foster reports more than a decade later. In the un-logged plot,"the major processes you'd follow in a forest -- the way nutrients are cycled, or the way water moves through the forest -- they were completely unchanged even though there was this catastrophe.

"In point of fact, disturbances are natural, ecosystems have tremendous resilience and great value -- human, environmental, educational -- comes from leaving disturbed areas alone and allowing them to recover naturally."

"Salvage harvesting policies after natural disturbance," D.B. Lindenmayer, Science, Feb. 27, 2004.

"Forest response to disturbance and anthropogenic stress," David Foster and John Aber, Bioscience, Jul/Aug 1997.

"Reorganization in a temperate forest following simulated hurricane blowdown," Cooper-Ellis, S., D. R. Foster, G. Carlton, and A. Lezberg. 1999, Ecology 80: 2683-2696.