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Telling the Forests’ Stories

A visit with Grant Elliott, Assistant Professor of Geography

By Jennifer Spitulnik
Published: - Topics: geography physical geography climate change global warming forests

Geography professor Grant Elliott’s research focuses on the movement of treelines in Alpine forests: it paints a sobering picture of the stunningly rapid rate of global warming. “The rate of forest change that we’ve been seeing in the last ten years has been pretty—I don’t know if ‘apocalyptic’ is the word, but it certainly deviates quite a bit from what we would consider the natural range of variability,” Elliott discloses. A global change ecologist, Elliott does not employ grandiose rhetoric—there is no need. Instead, the data gathered from his work as a dendroecologist clearly and irrefutably attests to the current unprecedented rate of climate change. Moreover, his research focuses on the effects of such change, not the causes, taking into account a local ecology’s past, present, and future.

By examining samples drawn from the cores of trees, Elliott uncovers the stories of forests and their response to a changing climate: “Forests change at a rate that is difficult for us to view, as humans, in our limited lifetimes,” Elliott explains. Indeed, with growth and development cycles that span 200-400 years, examining a tree’s rings provides key information on a forest’s history: “Being able to construct and reconstruct environments using tree rings gives us a better sense of the rate of change in forests,” he elaborates, and shows me a sample taken from an ancient tree—over four hundred years old—on Pike’s Peak. Pointing out how tiny the rings are, and how densely packed, Elliott comments, “the tree was pretty much rotten on the inside.” This, he relates, speaks to the tree’s tremendous age just as much as the density of its rings, because the dry air masses of the Rockies mean that trees rot much more slowly than they do in more humid climates like Missouri. Only a very old tree such as this one, Elliott indicates, would have had enough time to rot so completely. In just this way, dendroecologists like Elliott investigate the patterns gleaned by dendrochronology—tree-ring dating—and consider the ecological factors that would affect those patterns over time.

As global and local climates change, plants in turn adapt to variations in natural conditions. The current speed of climate change, however, is unprecedented since the last ice age. This means that over the last 12,000 years, there has never been a time when the globe has warmed as rapidly: “If you look at historical data since the peak of our last ice age—roughly the last 12,000 years—vegetation patterns have tracked climatic changes throughout the Holocene (the time since last glaciation),” Elliott remarks, adding, “Some species react differently to changes in climate than others, and temperature and moisture regimes are different now than they were even [as recently as] 100 years ago, so the rate of change that the climate system is undergoing is virtually unprecedented throughout the historic record.”

The changes in climate over time means that plants can grow and thrive in places where they previously could not. “I’m interested—I’m more than interested, I’m fascinated by—how plants react to changing natural conditions,” Elliott remarks. Plants’ reactions include adapting in place, but also, Elliott indicates, “they are also able to move elsewhere to where conditions may be becoming more conducive.” Whether they travel by wind, in the bodies of animals, or as a result of human intervention, plants can now grow in formerly hostile areas because rising temperatures have made new places—such as the high elevations of mountain peaks—more conducive to their survival. Large-scale patterns of climate change interact with local ecologies to shape the natural landscape, and Elliott studies the histories of these areas to predict their futures.

Elliott’s initial interest in forests and the variations in physical geographic landscapes over space and time began when he traveled with his family as a child. Their major vacations every year were to relatives in either Louisiana or Idaho, which, Elliott points out, are starkly different places from both physical and cultural standpoints. Coming from St. Louis, and comparing all of those places, Elliott was curious about how environments are shaped over time and how landscapes come to be so visibly different. “Physical geography offers you a comprehensive understanding of the processes and patterns that are at work forming the natural environment,” Elliott explains. That is true whether considering the wind erosion that resulted in Arches National Park in southern Utah, or gaining an understanding of how the forest at Rock Bridge State Park has changed over time, as his class had done earlier that day.

Elliott’s field research, which covers a wide geographic range in the western Rocky Mountains, has expanded to include local parks and urban forests. He has undertaken a local study of Rock Bridge State Park, appraising the ages of the trees and the forest’s species composition in order to predict what the park will look like in the future. Elliott relates that state officials are in the process of establishing a science school at the park, and his project will be linked with showing students how forests change over time.

This local involvement enriches his students’ learning. “I don’t necessarily subscribe to the idea that teaching suffers without research,” Elliott admits, “but it certainly does help and makes it more interesting if you can link them together.” Indeed, we witnessed this, accompanying his class on a field trip to Rock Bridge State Park. As soon as the class was fully assembled, Elliott began teaching—asking questions about the students’ assigned reading as we headed down the trail into the forest, making connections between theory and description. Elliott explained that until 1967, the entire park was agricultural fields; “Here,” Elliott announced, “we will see the biological result of reforestation—of the abandonment of pasture.” As they learned how to extract and record tree-core samples, students were able to see natural processes at work and witness how these shaped the local landscape. They gained knowledge available only from hands-on practice, like the sounds that different trees make when cored. At the end of class, Elliott acknowledged their work, telling them, “we have just set the foundation for further studies at Rock Bridge State Park.”

Elliott first came to Mizzou as an undergraduate student in 1996. Initially, he thought to pursue a career in healthcare; he very nearly flunked out. Elliott laughs, “my parents basically said ‘get it together, improve your grades or you’ll be moving back into our basement,’” which, he concedes, provided a lot of motivation. Browsing the catalog for interesting classes, he ended up choosing courses almost entirely within geography and meteorology. Once Elliott began these studies, he very quickly realized that he wanted to pursue graduate school and a career in physical geography and climate science.

As a graduate student at the University of Wyoming, Elliott ended up living in the back of his truck for two months in the San Juan Mountains in southwest Colorado. This hands-on field experience involved studying landscape through the use of repeat photography, a method of observing changes in the land by looking at historical photographs from previous U.S. Geological Surveys (USGS). These surveys, Elliott notes, were geared towards cataloguing the resources of the western parts of the country, so they tend to focus particularly on mineral-rich areas with potential for mining. Elliott intended to return to where those photographs were taken in the late 1800s and early 1900s, take new photographs, and compare how the landscape had changed over time. But, Elliott reveals, that was a summer with many forest fires. As such, his photographs are clouded with smoke, making it difficult to do the kind of study he intended. “You can see two different sets of forests in the photos,” Elliott describes, “But it’s hard to tell when the changes happened specifically between 1890 and 2002.” In order to pinpoint the dates of various changes in the landscape, Elliott began taking tree-core samples and using them to create a timeline of events.

For his doctoral work at the University of Minnesota, Elliott took up dendroecology more deliberately, examining high-elevation forests in the Rocky Mountains to evaluate, as he describes, “if warmer temperatures have promoted the upslope development of the forested belt,” that is, he studied how treelines are encroaching ever upwards into Alpine tundra—treeless areas at mountain peaks. Because it is too cold at those elevations for the forest to continue, trees cannot successfully regenerate and grow. As such, Alpine peaks remain the domain of shrubs and snow pack. However, as the climate warms globally, trees are now able to grow at higher and higher elevations. Hence, the treeline moves upwards in altitude. By paying attention to these upward encroachments of treelines, Elliott contributes to our understanding of how wide scale changes in air mass climatology influence vegetation on a broad geographic scale.

Advancing treelines most directly impact human populations because they decrease the area available for snowpack, the layers of snow that accumulate on mountain peaks. Dry climates like those in the western United States rely on snowmelt—the surface runoff from melting snowpack—to supply streams and reservoirs with fresh water: “These high elevation areas are basically like our water towers,” Elliott explains, because it is on these peaks that snowpack persists for the longest. In this way, forests’ encroachment on Alpine tundra at ever higher elevations measurably decreases water supply for humans and other animals.

Warming temperatures also affect plant and animal interactions. Elliott’s current projects study previously unseen interactions, or, as he qualifies, “at least not for the last 10,000 years.” The spruce beetle, for example, is now able to attack trees at the uppermost forest limits. Spruce beetles—insects that bore into the bark of a tree and disrupt the flow of nutrients from the soil to the canopy, thus killing the tree—are able to survive at elevations that were too cold for them as recently as ten years ago. Due to winter warming, Elliott explains, treelines are actually receding because of spruce beetle induced mortality. That is, whereas it was formerly too cold for spruce beetles to survive the winter on mountain peaks, the insects can now prey on trees at increasingly higher elevations throughout the year. The mortality rate of spruce beetle-infected trees is 100%, which makes this consequence of global warming observable even within the brief span of a human life. For example, when Elliott returned to one of his dissertation study sites in 2015 for the first time since 2008, two entire stands of trees had been completely wiped out by spruce beetles. Elliott is interested in investigating these kinds of biotic disturbance events: insect-vegetation interactions that would not have affected trees at such high elevations prior to warmer global temperatures. Elliott’s other collaborations, such as one studying snowpack and forest regeneration in windswept areas, also address such interactions between climate and vegetation, insects and trees.

Taken in total, Elliott’s work tracks the history of forested areas and maps out their futures: “All of these intricate webs of climate influences and local scale influences combine to create the landscape mosaic that currently exists,” he emphasizes. His research tells forests’ stories; as he said to his students, “we can tell the story of what this area used to be.”