Cold War aerials provide conservation tool for grasslands thanks to Missoula scientists

BILLINGS – Aerial imagery collected during the Cold War to help the Army plan for the possibility of infantry mobilization and artillery siting on U.S. soil is helping scientists understand where trees have branched out across Montana’s prairie landscapes.

Scott Morford used 170,000 of the black and white photos (40 terabytes of information) to help create the Landscape Explorer. By logging on to the website, users access a divided screen showing the historic photographs on the left which can then be compared with modern, full-color Google Earth images of the same area on the right.

Right clicking on the historic image will provide details on when the photo was taken.

It’s like having your own visual time machine: Here’s a house in 1950, on the left, surrounded by empty fields, compared to the crowded neighborhood where it’s situated now, on the right. So tree incursions is not all the photos reveal.

“We have this one chance for a special look back in time,” said Dave Naugle, an associate professor of wildlife biology at the University of Montana who collaborated on the project. “And time often, especially in conservation, brings perspective.”

In the past, Naugle noted, rangeland professionals and scientists used satellite imagery to evaluate vegetation changes on the landscape. Those datasets, however, only go back to the 1980s, some not even that far.

Go tree, go

The expansion of treed habitat interests Naugle because in places like the Pryor Mountains south of Billings, or the Blackfoot River valley west of Missoula, Landscape Explorer-Montana shows how conifers like juniper and Douglas fir have moved into what used to be sagebrush rangelands.

“You can use Landscape Explorer to see that slow, insidious effect of trees taking over rangelands where trees don’t belong,” Naugle said.

The encroachment of trees is a threat to sagebrush-dependent species like sage grouse. The big birds don’t like anything tall that predatory birds can sit on, so they will avoid those landscapes.

“A few years ago we published a paper from Oregon where we took all the sage grouse leks and mapped current trees, and that paper showed that with only 4% tree cover in rangelands – which is like two to four trees per acre, not much – all the sage grouse males abandoned the leks,” Naugle said.

No male birds meant no breeding occurred in those areas, a wake-up call to the researchers that tree growth had serious impacts on sage grouse.

“In comparison to some of the other threats in the sagebrush biome, woodland encroachment is kind of one of the newer kids on the block,” Naugle said.

Crowded out cows

As more trees move into grasslands, grazing acreage for ranchers is also reduced.

Based on Landscape Explorer, Working Lands for Wildlife estimated since the 1950s trees have moved into more than 7.4 million acres of Montana’s 48 million acres of rangeland. That loss of habitat equates to $11.5 million in forage.

Working Lands for Wildlife also said more than 60% of the nation’s wildland fires occur on grass and shrublands where trees enable fires to become more severe, harder to control and more difficult to extinguish.

“Understanding where and how trees have moved across Montana’s sagebrush country gives landowners and managers insight on where to work to protect intact cores from woody encroachment,” the Working Lands website said. “The Landscape Explorer application helps communicate the degree and scale of this threat.”

Montana NRCS is geared to helping landowners take action on issues like improving grassland habitat by providing technical and financial assistance. Conservation districts and the Montana Department of Natural Resources and Conservation have also assisted.

“Landscape Explorer-Montana is remarkably powerful,” Morford said. “Ranchers and range managers can zero in on places to prioritize restoration, wildfire professionals can see how the wildland urban interface has shifted, civic leaders can analyze growth patterns over decades, and everyday Montanans can see how their neighborhood, town, or favorite natural space has changed over time. It’s pretty cool.”

Other uses have included analyzing changes in glaciers, sand dune migration and in water rights disputes to examine when a parcel may have first been irrigated.

“We’ll never fully understand all of the applications of this,” Naugle said.

Heat mapping trees

For Montana, the personal time machine has an added gadget. A slider tool highlights where trees have filled in grasslands compared to the 1950s, signified by yellow, white and red squares to create a heat map. Red being the most encroachment, followed by yellow and then white. The heat map was created by using artificial intelligence to compare the old and modern images.

“When we started the project, it was really a tool to understand conifer encroachment to rangeland,” said Morford, a researcher at the University of Montana’s Numerical Terradynamic Simulation Group. “Tree cover changes slowly through time, so people don’t realize how extensive trees are moving into rangeland ecosystems, both in Montana and across the West.”

Morford came up with the idea while working on a project for the Nature Conservancy in southwest Montana in 2017. He used specialized software to stitch the old images together. Then an interactive online mapping application was built allowing users to zoom in and out on locations and move between the historical and current images.

Officials at Montana NRCS saw his brainchild and wanted to expand the project to the entire state. They saw it as a tool to promote conservation and talk about how landscapes are changing, he said.

In comparison to the entire West, Montana only required 18,000 images from the U.S. Geological Survey’s storage vaults. Those old photos have a resolution of about 1 to 2 meters depending on the height the reconnaissance plane was flying. In comparison, modern technology has a resolution of 6 inches or less.

After a year-and-a-half, the Montana project was completed. Then folks at the Bureau of Land Management and the Intermountain West Joint Venture found out about the work. The BLM and the bird habitat conservation group funded expanding the Landscape Explorer program to the entire West.

The final product was developed over two-and-a-half years with help from four different part-time and full-time programmers. The first public release was in July 2023 with all 17 western states completely done by October. The Montana project, with its additional functionality, was accompanied by a scientific paper published in fall with the final touches added for its full release to the public in March.

“We’re not suggesting the 1950s is the baseline,” Morford said. “What we’re saying is this gives us a way to look at rates of change.”