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Our Changing Forests: An 88-Year Time Lapse

1909. Facing nearly due west from ridge northeast of Como Lake. Light selection cut in open ponderosa pine. Ground cover is comprised of perennial grasses and forbs, including basalmroot. A few low-growing bitterbrush plants can be seen in the vicinity of horses and in distance on left. A group of willows can be seen behind horsemen at left center. (U.S. Forest Service)closemore
1909. Facing nearly due west from ridge northeast of Como Lake. Light selection cut in open ponderosa pine. Ground cover is comprised of perennial grasses and forbs, including basalmroot. A few low-growing bitterbrush plants can be seen in the vicinity of horses and in distance on left. A group of willows can be seen behind horsemen at left center. (U.S. Forest Service)

Intense forest fires have been raging across the western United States this summer. So far this year, nearly 43,000 wildfires have torched almost 7 million acres of land.

As NPR Science correspondent Christopher Joyce and photographer David Gilkey report from Arizona and New Mexico this week, the forests of the American Southwest have become so overgrown that they're essentially tinderboxes just waiting for a spark.

1909. Looking northeast through a more heavily stocked ponderosa pine stand. The ground cover around C.H. Gregory (in distance) and W.W. White is predominantly herbaceous species with a high incidence of basalmroot. The dark low-growing shrub around White appear to be snowberry. Large willows are evident on the left edge of the photo and in front of White. (Original captions) (U.S. Forest Service)
1909. Looking northeast through a more heavily stocked ponderosa pine stand. The ground cover around C.H. Gregory (in distance) and W.W. White is predominantly herbaceous species with a high incidence of basalmroot. The dark low-growing shrub around White appear to be snowberry. Large willows are evident on the left edge of the photo and in front of White. (Original captions) (U.S. Forest Service)

This "tree epidemic" stems from Forest Service policy dating back to the early 1900s of aggressively fighting all forest fires. But regular, small fires clean out dead wood, grasses and low brush — and if fires are quashed, the forest just grows into fuel. And that's why we see more of these mega-conflagrations today.

In trying to tell the story of our changing forests, we turned to the U.S. Forest Service for some historical context. Buried in the back of General Technical Report No. 23 was the pay dirt: a stack of 13 series of photos, more than 88 years in the making.

The photographs document the life of the Bitterroot National Forest in west-central Montana, from 1909 to 1997, though the project is still ongoing. Every 10 to 15 years, photographers return to the same 13 spots in the forest.

Bitterroot is a managed forest — meaning that foresters periodically trim, cut and thin the land — and the photo series is meant to show how dynamic the forest is with management, says Michael Harrington, a research forester with the Missoula Fire Science Lab. Through the nine-image sets, we can see trees grow and thicken, the effects of selective logging and also how quickly the forest land rebounds.

It's important to note that the first images in each series, from 1909, are not the "original" state of the forest. The project was started when photographer W.J. Lubkin was sent from Washington, D.C., to document logging activity on the land after it was sold and selectively cut in 1906.

1927. 18 years later. Two willows in the 1909 scene have grown considerably and now contain many dead branches. Other willows have become established in midground, while young ponderosa pine can be seen in localized areas. The herbaceous ground cover persists. Taken later in the season, this view pictures basalmroot at a cured stage of growth. Note fire-scarred stump on the right.  (U.S. Forest Service)
1927. 18 years later. Two willows in the 1909 scene have grown considerably and now contain many dead branches. Other willows have become established in midground, while young ponderosa pine can be seen in localized areas. The herbaceous ground cover persists. Taken later in the season, this view pictures basalmroot at a cured stage of growth. Note fire-scarred stump on the right. (U.S. Forest Service)

He captured the initial images using a 6.5-by-8.5-inch view box camera and glass plates, but "the camera points were not permanently marked because this was not part of the assignment."

But later photographers K.D. Swan and W.W. White found the locations in 1925, which were staked with bronze caps in 1938. In the Forest Service report, Swan recalled how White found the original photo points:

1938. 29 years later. Young pine growth is beginning to occupy localized sites in the understory. A tree on right has blown down, and the willow in the foreground that was present in 1909 has become senescent. In the foreground, the low shrub component is less evident, but this may be a seasonal difference. (U.S. Forest Service)
1938. 29 years later. Young pine growth is beginning to occupy localized sites in the understory. A tree on right has blown down, and the willow in the foreground that was present in 1909 has become senescent. In the foreground, the low shrub component is less evident, but this may be a seasonal difference. (U.S. Forest Service)

The quest was extremely fascinating. White had a good memory and was able to spot, in a general way, the locations we were after. Peculiar stumps and logs were a great help. Just when we might seem baffled in the search for a particular spot, something would show up to give us a key. The clue might be the bark pattern on a ponderosa pine, or perhaps a forked trunk.

The camera we were using duplicated the one used for the original pictures, and when a spot was once found it was a simple matter to adjust the outfit so that the image on the ground glass would coincide with the print we were holding. It was an exciting game, and we felt it was more fun than work.

Copyright NPR 2016.

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