Faces of Climate: Andrew Hansen

EDITOR’S NOTE: In our new series, “Faces of Climate,” Mountain Journal is highlighting good work in Greater Yellowstone. As the climate changes the face of the landscape, these people are changing our approach to it. Through interviews and imagery, these are your “Faces of Climate.”

CORRECTION: An earlier version of this article stated Hansen attended the University of Washington in Bellingham, Washington. He attended Western Washington University in Bellingham.

Andrew Hansen has early memories of how poignantly people can impact the environment. He grew up on a farm in Pennsylvania with a river running through it. The water was polluted by an upstream paper mill.

“I really got interested in how people can affect nature and landscapes, and this was just when the Endangered Species Act was coming into being and the Clean Water Act,” says Hansen, a professor emeritus who retired from Montana State University last year after 33 years of teaching ecology. “I got interested in trying to … heal nature, but all the while I was quite compelled to see wild nature, unlike the area I grew up in.”

And to meet those ends, he hitchhiked west.

Hansen went on to earn an undergraduate degree at Western Washington University in Bellingham and a doctorate through the University of Tennessee, which led him to Alaska to study bald eagles. His research interests since then have focused on the human impacts on places they live and how mimicking natural ecological changes can sustain biodiversity.

In southeast Alaska, Hansen was introduced to what he calls “natural forests,” those relatively undisturbed by human activity. In contrast, he worked at Oregon State University on the effects of clearcutting and produced a study on managing and sustaining biodiversity in forests.

“It was really an early contribution to ecological forestry approaches that basically argued mimicking natural disturbance was a way to better sustain biodiversity in forests, leaving some live trees and leaving dead trees on site,” Hansen says. The idea was that leaving some “patchy” spots with both living and dead trees promotes biodiversity.

Hansen arrived at MSU in 1993 just as clearcutting at the western boundary of Yellowstone National Park was getting attention. He studied clearcutting effects on wildlife in that part of the Greater Yellowstone Ecosystem as compared with the impacts of the 1988 Yellowstone fires.

Living in the Gallatin Valley tuned Hansen into how crucial soil, elevation and climate are to biodiversity. He began noticing that he lived in a place with fertile soil and an ideal climate for agriculture. This led to a bigger realization: that most agriculture and rural development in the Gallatin Valley happened in places better suited for biodiversity.

Hansen and his research teams decided to map the intersection of urban and rural land to better understand that overlap.

Using satellite imagery, they were able to compile locations of urban areas and farms. Data from wells written on paper cards from the basements of 20 county planning offices provided coordinates of homes and showed the researchers how closely the two were linked.  

“When we first saw the map, I just couldn’t believe it,” Hansen says. “Pretty much all of the GYE was ringed with rural subdivisions and rural homes.”

Ecologists hadn’t done a lot of work on rural residential development, Hansen said. They often considered it a friendly use of the land when executed sustainably.

But it became clear that rural homes were impacting nearby wild spaces, which led Hansen to understand how “edge effects” can alter biodiversity on public lands: groundwater degradation from septic systems, pets preying on or displacing native wildlife, or invasive plants moving in. He went on to study these effects in Greater Yellowstone and five other protected areas and ecosystems around the world.

Undeveloped private lands, Hansen says, should remain natural habitat and should not be degraded by subdivision construction or intense land use. Yet he also recognizes that certain development will happen even while one maintains landscape integrity for those places with high ecological value. Combining these considerations, Hansen says, allows land managers to prioritize areas for conservation easements, places that are valuable for wildlife and ecological function, and also likely to be developed.

“You could live out with a light touch or a heavy hand,” he says, “and so I think we have a real opportunity to try to communicate with homeowners and help them know how to have a light touch.”