Science

Our Changing Forests: An 88-Year Time Lapse

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.

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.

  • 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. (Original captions)
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    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. (Original captions)
    Photo 87357/U.S. Forest Service
  • 1925. 16 years later. Bitterbrush plants on left and willow in distance, more evident in the winter scene, have increased in size. Young conifers are beginning to fill the understory in the background.
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    1925. 16 years later. Bitterbrush plants on left and willow in distance, more evident in the winter scene, have increased in size. Young conifers are beginning to fill the understory in the background.
    Photo 204815/U.S. Forest Service
  • 1938. 29 years later. Several pines in foreground have been cut, some have died, and others have fallen. Ponderosa pine and Douglas-fir regeneration is profuse, while the willow in the distance is larger. Bitterbrush has increased, but regeneration appears minimal. Slash and windfall have resulted in an increase in heavy fuels. Mullein can be seen in foreground for the first time.
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    1938. 29 years later. Several pines in foreground have been cut, some have died, and others have fallen. Ponderosa pine and Douglas-fir regeneration is profuse, while the willow in the distance is larger. Bitterbrush has increased, but regeneration appears minimal. Slash and windfall have resulted in an increase in heavy fuels. Mullein can be seen in foreground for the first time.
    Photo 361704/U.S. Forest Service
  • 1948. 39 years later. Open view is screened by growth of young conifers. Bitterbrush plants have continued to grow, but are beginning to receive competition from conifers for space. Willow in distance has been overtopped by conifers. Dead trees have toppled, adding to fuel load. Slash in foreground has decomposed somewhat, while basalmroot is not evident and mullein has increased.
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    1948. 39 years later. Open view is screened by growth of young conifers. Bitterbrush plants have continued to grow, but are beginning to receive competition from conifers for space. Willow in distance has been overtopped by conifers. Dead trees have toppled, adding to fuel load. Slash in foreground has decomposed somewhat, while basalmroot is not evident and mullein has increased.
    Photo 452369/U.S. Forest Service
  • 1958. 49 years later. Growth of young ponderosa pine and Douglas-fir dominate skyline, thereby obscuring view of the few remaining mature ponderosa pine in the distance. Competition by young pines in foreground has apparently caused several of the bitterbrush plants to deteriorate. Heavy ground fuels show considerable decomposition.
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    1958. 49 years later. Growth of young ponderosa pine and Douglas-fir dominate skyline, thereby obscuring view of the few remaining mature ponderosa pine in the distance. Competition by young pines in foreground has apparently caused several of the bitterbrush plants to deteriorate. Heavy ground fuels show considerable decomposition.
    Photo 487738/U.S. Forest Service
  • 1968. 59 years later. Precommercial thinning and pruning in 1968 removed mature pines and opened up young pine stand. This benefitted some bitterbrush plants, but those in left foreground under and near leave trees show further deterioration. Slash has added to heavy fuels, while down material is more decomposed.
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    1968. 59 years later. Precommercial thinning and pruning in 1968 removed mature pines and opened up young pine stand. This benefitted some bitterbrush plants, but those in left foreground under and near leave trees show further deterioration. Slash has added to heavy fuels, while down material is more decomposed.
    Photo 518767/U.S. Forest Service
  • 1979. 70 years later. Understory is dominated by increased pine growth that is shading out bitterbrush. Past disturbance has allowed knapweed to predominate in foreground.
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    1979. 70 years later. Understory is dominated by increased pine growth that is shading out bitterbrush. Past disturbance has allowed knapweed to predominate in foreground.
    U.S. Forest Service
  • 1989. 80 years later. Growth of trees in the foreground has reduced the view. A few bitterbrush plants can be seen in the center of the stand, along with some grasses.
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    1989. 80 years later. Growth of trees in the foreground has reduced the view. A few bitterbrush plants can be seen in the center of the stand, along with some grasses.
    U.S. Forest Service
  • 1997. 88 years later. Thinning in 1992 has created large openings throughout the stand. Only mid- and back-ground received burn treatment in 1993, resulting in loss of small trees. Bitterbrush in unburned foreground looks more vigorous than others in burn area. Ground cover is dominated by spotted knapweed, elk sedge and bluebunch wheatgrass.
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    1997. 88 years later. Thinning in 1992 has created large openings throughout the stand. Only mid- and back-ground received burn treatment in 1993, resulting in loss of small trees. Bitterbrush in unburned foreground looks more vigorous than others in burn area. Ground cover is dominated by spotted knapweed, elk sedge and bluebunch wheatgrass.
    U.S. Forest Service

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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.

  • 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)
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    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)
    Photo 86469/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.
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    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.
    Photo 221280/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.
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    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.
    Photo 354400/U.S. Forest Service
  • 1948. 39 years later. Two mature pines have fallen to the ground. Growth of young pines are closing in portions of the understory. Young pine at right foreground is screening senescent willow. Herbaceous plants and snowberry in foreground have put on good growth.
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    1948. 39 years later. Two mature pines have fallen to the ground. Growth of young pines are closing in portions of the understory. Young pine at right foreground is screening senescent willow. Herbaceous plants and snowberry in foreground have put on good growth.
    Photo 452641/U.S. Forest Service
  • 1958. 49 years later. A shelterwood cut in 1952 removed several of the merchantable trees and left slash on the ground. Plants occupying sites near left edge of photo appear to be betterbrush.
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    1958. 49 years later. A shelterwood cut in 1952 removed several of the merchantable trees and left slash on the ground. Plants occupying sites near left edge of photo appear to be betterbrush.
    Photo 487747/U.S. Forest Service
  • 1968. 59 years later. A 1962 selection cut and 1966 precommercial thinning have resulted in a more open landscape with increasing slash on the ground. Bitterbrush plants are more evident, while willows in the midground have been favorable influenced by removal of young conifers.
    Hide caption
    1968. 59 years later. A 1962 selection cut and 1966 precommercial thinning have resulted in a more open landscape with increasing slash on the ground. Bitterbrush plants are more evident, while willows in the midground have been favorable influenced by removal of young conifers.
    Photo 518770/U.S. Forest Service
  • 1979. 70 years later. Rapid establishment and growth of new conifers has screened the open view of 1968. Growing conditions for bitterbrush and willow have deteriorated because of competition for sunlight and moisture. Partial cutting and thinning in 1952, 1955, 1962, and 1966 have allowed more conifer regeneration than the early, light 1906-9 cut.
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    1979. 70 years later. Rapid establishment and growth of new conifers has screened the open view of 1968. Growing conditions for bitterbrush and willow have deteriorated because of competition for sunlight and moisture. Partial cutting and thinning in 1952, 1955, 1962, and 1966 have allowed more conifer regeneration than the early, light 1906-9 cut.
    U.S. Forest Service
  • 1989. 80 years later. The small trees established shortly before the 1979 photo have grown into a thicket of saplings.
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    1989. 80 years later. The small trees established shortly before the 1979 photo have grown into a thicket of saplings.
    U.S. Forest Service
  • 1997. 88 years later. This stand was not subject to management activities in 1992 and 1993. Note the rapid growth of the Douglas-fir trees in the foreground since 1989, masking the view of the slower growing ponderosa pines in the background. Undergrowth is primarily pinegrass and dogbane.
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    1997. 88 years later. This stand was not subject to management activities in 1992 and 1993. Note the rapid growth of the Douglas-fir trees in the foreground since 1989, masking the view of the slower growing ponderosa pines in the background. Undergrowth is primarily pinegrass and dogbane.
    U.S. Forest Service

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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:

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.

A map showing the locations of 13 photo points in Bitterroot National Forest, where photographers have returned since 1909. i i

hide captionA map showing the locations of 13 photo points in Bitterroot National Forest, where photographers have returned since 1909.

General Technical Report 23/U.S. Forest Service
A map showing the locations of 13 photo points in Bitterroot National Forest, where photographers have returned since 1909.

A map showing the locations of 13 photo points in Bitterroot National Forest, where photographers have returned since 1909.

General Technical Report 23/U.S. Forest Service

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