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Photos show changes in SE vegetation

Presentations tonight illustrate recovery after glaciers, logging

Posted: Friday, January 07, 2005

Last summer, Richard Carstensen, Kathy Hocker and Terry Schwarz tramped through the woods with an 8-megapixel digital camera in an ongoing quest to re-take historical photos as old as 110 years.

Their 15 pairs of "before and after" photos illustrate how Southeast Alaska vegetation has recovered, or changed, as glaciers have melted, forests have been logged and mines and farms have been abandoned.

"We're not trying to document damage," said Carstensen, a naturalist with Discovery Southeast. "We're trying to show how the natural vegetation recovery process varies."

Carstensen, Hocker and Schwarz will present "Repeat Photography: Studying Successional Change by Retaking Historical Photographs," at 6:30 and 8 p.m. tonight as part of the Mendenhall Glacier Visitor Center Fireside Chat. Admission is free.

The project is a two-year collaboration with the U.S. Forest Service's Alaska branch of State and Private Forestry and the research group SEAWED (Southeast Alaska Wilderness Exploration Analysis and Discovery).

In 1989, Carstensen was on the Mount Roberts Tram, looking at 40-year-old photos of the area taken by late Juneau naturalist Donald Lawrence, his mentor.

He retook a few and learned so much about vegetational change in the area that Michael Shepherd, of the Forest Service, created the project.

Lawrence was interested in what was happening in the sub-alpine meadows near the tree line on Mount Roberts. It's comparable to what's happening in glacier valleys, according to Carstensen.

Two hundred years ago, the bowl to the left of the tram, as you climb the ridge, would fill with snow. The snow remained in the summer and killed off part of the forest.

Summer temperatures have increased since then, to the point where that bowl has no snow for part of the year. As a result, the meadow has reappeared. It will slowly turn into a forest, Carstensen said.

"(Lawrence's photo) shows a combination of a sub-alpine meadow interfingering with some alder trees," said Hocker, also a naturalist with Discovery Southeast. "In the 50 years since that photo was taken, the alders have invaded the entire photo frame. It indicates that our climate is getting a little warmer."

Carstensen, Hocker and Schwarz use an 8-megapixel digital camera on a tripod. They can upload the historical photo into the camera. Once they think they've re-captured the exact frame for their new photo, they can look through the viewfinder and toggle back to the historical print.

They use the Photoshop computer program to turn the new photograph into a transparency, which they lay over the original historical photo. From there, they can crop the re-take until it matches perfectly with the historical photo.

Carstensen, Hocker and Schwarz have recreated mining camp photos from the 1920s and 1940s photos of Valley farmland. Schwarz even climbed to the top of Mount McGinness last summer to recapture an 1893 photo of the Valley.

Many of the historical photos are not labeled, making it difficult to pinpoint their exact location. The group has used ArcMap, a computerized mapping program, to plot bearing lines and line up mountain ridges.

One photo by the commercial photographers Winter & Pond confounded Carstensen and Hocker. With ArcMap, they pinpointed the exact spot where the photographers were standing in Eagle Valley, along the old tram route to the now-vanished town of Amalga.

"We want our historical photographs to be nice and sharp with good foreground detail. A sharp background helps for relocation," Carstensen said. "Aside from that, we're looking for different kinds of succession to document."

Some of their paired photos show areas of the Lower Mendenhall Valley, used in the mid-20th century to graze cattle and grow hay and potatoes. Many of those areas have reverted back to meadows.

About 200 years ago, the Mendenhall Glacier extended halfway into the Valley, and the Juneau Icefield and Glacier Bay were coated with much thicker ice. As those glaciers have melted, Carstensen said, the land has been rising. In downtown Juneau, the rate is about a half an inch a year, he said.

"It's the opposite of what's happening around the rest of the world," Carstensen said. "The water is rising around the world, and it's rising here too, but our land is rising at a faster rate and promises to do that for the forseeable future."

• Korry Keeker can be reached at korry.keeker@juneauempire.com.



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