During the summer of 1988, with much of the United States experiencing serious drought, and discussions swirling about the global environmental toll of greenhouse gases, persistently dry and windy conditions in the West combined to produce the most expensive wildfire event the U.S. had ever seen.
Before it was over, 51 individual wildfires combined to torch nearly 800,000 acres, or 36 percent, of Yellowstone National Park, roughly the size of Rhode Island. In a single August day, wind-fanned flames consumed 150,000 acres. Including lands outside the park, the fires burned 1.2 million acres of forest. The months-long battle brought 25,000 federal firefighters onto the fire lines and cost $120 million. Smoke from wildfires in and around Yellowstone darkened the sky up and down the Rockies and far and wide across the Great Plains.
It was a year that seared wildfire and the government response to wildfire into the national consciousness.
A quarter of a century after the touchstone events of 1988, the American West has seen a dramatic increase in large wildfires tied to drought and a warming climate. In Australia, where warming has produced catastrophic wildfires that seem as seasonal an occurrence as monsoonal rains, the press has taken up a new term: “megafires.”
In addition to showcasing how large wildfires can impact an entire region, the fires of 1988 also turned the Greater Yellowstone Ecosystem into one of the world’s great laboratories for the study of forests and fire. Research into the Greater Yellowstone Ecosystem’s history with wildfire is helping scientists at Montana State University, along with an international team of collaborators, understand how fire, climate and human behavior converge to shape the ecosystems of temperate forests around the world.
A project called WildFIRE PIRE, funded by a five-year, $3.85 million Partnership in International Research and Education (PIRE) grant from the National Science Foundation and a core project of the Montana Institute on Ecosystems, is working to build detailed pictures of past and present fire activity and the influence of wildfire on the landscapes of three continents. In addition to its focus on historic fires, the group is building computer models that will project how those dynamics might play out in the future. The group will use thousands of years worth of historical data on landscape vegetation, fire, human behavior and climate to build a computer simulation to understand how future changes in climate and human factors might affect vegetation patterns in Earth’s forests.
For Cathy Whitlock, MSU professor of earth sciences, principal investigator for WildFIRE PIRE and co-director of the Montana Institute on Ecosystems, the 1988 fires kindled a desire to better understand how fire ecology was woven into the hidden narrative of the Greater Yellowstone Ecosystem, which has evolved over the 14,000 years since the last great glaciers melted away. During 20-plus years of exploration into the paleoecology of Yellowstone, Whitlock has pioneered many of the techniques used for delving into a landscape’s history to better understand the role of wildfire in an ecosystem.
Whitlock’s research is now the foundation of WildFIRE PIRE’s international efforts.
“The research that we started in Yellowstone after 1988 essentially gave birth to the discipline of paleofire ecology,” Whitlock said. “And the studies in Yellowstone have inspired fire history investigations around the world.”
Much the way forensic investigators tease the story of an event from microbes and chemical traces at a crime scene, Whitlock and her fellow paleoecologists examine ancient clues such as pollen and charcoal pulled from lakebed sediments. This evidence from the paleo record, combined with historical climate data, helps them build a picture of ecosystem change dating back thousands of years. It is a picture that details the climatological drivers of large conflagrations, like the fires of 1988, as well as the ecological changes that wildfire has wrought.
For Whitlock and other WildFIRE PIRE scientists, to walk in the Gallatin Range or the Absarokas is to venture into a mystery. What forces shaped the patchwork of vegetation in this corner of the Greater Yellowstone Ecosystem—when were the present-day high-elevation forests of whitebark pine, fir and spruce formed? What is the history of the groves of aspen and cottonwood in Yellowstone’s Northern Range? Why have the vast expanses of lodgepole pine forest persisted with little change for the last 11,000 years? And, how are human activities and a changing climate shaping what this landscape will look like in the future?
In addition to the Rockies, WildFIRE PIRE is researching similar questions in the Andes of Chile, in Australia along the western mountains of Tasmania, and in the Southern Alps of New Zealand, among other locations.
“We’ve learned that fire is one of the major drivers of change within the temperate forest ecosystems worldwide,” Whitlock said. “Our research shows that both people and climate have played a role in how those changes occur.”
The New Zealand experiment
The Māori people first set foot in New Zealand roughly 700 years ago, making it one of the last major colonizations on Earth. When they landed, they brought fire to a heavily forested landscape where fire was naturally rare. That makes it an ideal place for the WildFIRE PIRE team to study the impacts that humans can have through deliberate burning, even in the absence of climate change.
The question was simple: What did ecological change look like after the Māori began to open up the landscape by burning New Zealand’s native stands of podocarps (conifers) and nothofagus (southern beech) that once stretched unbroken for thousands of square miles?
“The change was more dramatic than we had ever imagined,” said David McWethy, an ecologist and assistant research professor in the Department of Earth Sciences at MSU.
McWethy said because New Zealand native forests were not adapted to fire, the Māori were able to permanently remove beech and podocarp forest in just a couple of decades, and that he couldn’t find another example anywhere on Earth where such an enormous landscape was transformed that fast.
McWethy and Whitlock have been working with New Zealand scientists Janet Wilmshurst, Matt McGlone and George Perry to investigate the historic ecological record stored in New Zealand’s lake sediments. Their findings, published in several international academic journals, suggest dramatic forest conversions occurred within decades of human arrival in New Zealand. McWethy said the group compared the field observations with a computer simulation built by Perry that considers the relative importance of human-set fires, climate and fuel conditions in causing the transformation.
Previous studies estimated it had taken a century or more to produce the vast grasslands that have replaced much of the podocarp and nothofagus forest in New Zealand.
McWethy said results from Perry’s simulation model strongly suggest that the Māori-set fires created large openings of highly flammable grasslands and shrub lands within what had previously been closed-canopy forests of large, mature beech and podocarps. Those initial openings dried out the forest along their borders, allowing for multiple new burns to open new gaps in the forest, leading to a mosaic of grassy corridors that dried out the forest even further—a self-reinforcing cycle that created fire-prone landscapes. They also found that the British colonization of New Zealand that began with the treaty of Waitangi in 1840 was followed by equally dramatic landscape transformation—large fires that were used to clear land for grazing.
McWethy said the scientists took 30 lake cores and were able to corroborate some of the earlier data on the vegetation change, as well as more precisely determine how the destruction of the forest happened and why it happened so fast.
In successive years, this process expanded, until the scale was tipped entirely, McWethy said. In a matter of a couple of decades, not centuries, large tracts of old forest were burned and converted to open grass and shrub lands, an example of a rapid and persistent human footprint on the landscape.
Invasions and forest ecology
Bruce Maxwell, an MSU professor who specializes in plant invasion biology, said his WildFIRE PIRE research is tracking present-day changes in New Zealand, Chile and the United States that are altering the natural fire regimes and having profound consequences for future biodiversity.
In New Zealand’s Southern Alps, the emergence of lodgepole pine as an invasive species highlights the profound differences between the primeval forests that greeted the Māori and the landscape that has developed since European settlers began to exert their influence. Maxwell said it also highlights the ecological ripple effect of modern choices in forest management. The spread of this invasive species can be seen with the naked eye as lodgepole pine forests migrate from the erosion zones where they were planted after human-set fires cleared native forest from the mountainsides.
“You can see where the prevailing winds are pushing the lodgepole seedlings into new terrain,” Maxwell said. “It’s ironic, because now the government that encouraged planting of this species in the first place is spending a lot of money to kill lodgepole pine, especially in the key dispersal zones.”
Maxwell pointed out that the pine expansion—a threat to native biodiversity—has been happening without the influence of wildfire. Ironically, this invasive species from North America thrives with frequent burning—wildfire gives lodgepole a boost in the dispersal of seeds—and it has been introduced into New Zealand’s forest where native plants are poorly adapted to survive a wildfire.
Should non-native lodgepole stands get hit with fire, what might have been a slow wind-driven expansion of its seedlings could explode into something that would forever change the ecological balance of the landscape, Maxwell said.
Maxwell found a similar problem lurking with lodgepole pine in southern Chile and Argentina, where landowners planted the relatively fast-growing trees as a timber crop to supply wood and paper mills. Much like in New Zealand, the stands have begun to jump the boundaries their planters intended for them, and spreading pine seedlings are changing the natural fire conditions.
Many of these plantations have already been burned, Maxwell said, and the odds are good that they will continue to be the source of fires into the future. Much the way the native beech and podocarp forest was lost through the introduction of fire by the early Māori in New Zealand, Maxwell said the expanding range of lodgepole pine in South America is increasing the risk of fire and threatening the biodiversity along the flanks of the Andes.
The long view in Australia
MSU postdoctoral researcher Gabriel Yospin said the paleo record from Australia’s subalpine landscape offers a glimpse of the long-range ecological impact of human-set fires—the Aborigine culture in Australia dates back about 50,000 years.
Yospin made two trips to Tasmania’s Cradle Mountain-Lake St. Clair National Park to pull lakebed cores and measure the vegetation. Yospin said millennia of prehistoric fire management combined with the area’s relatively wet climate have fostered a diverse array of vegetation, including subalpine rainforests, a mix of drier forest and shrub lands, as well as button grass moors. But climate change and the loss of native burning practices are already beginning to shift this balance, Yospin added.
The data collected at Cradle Mountain are also beginning to animate one of the computer models built by Bob Keane of the U.S. Forest Service Rocky Mountain Research Station, a member of the WildFIRE PIRE team.
Computer modeling has become a major tool for ecologists, particularly as they attempt to predict how different ecosystems will behave under various environmental influences, such as a warming climate, increased logging or the introduction of a non-native species. WildFIRE PIRE is employing simulation modeling to understand the landscape ecology of sites like Cradle Mountain. The historical data show the effect that climate, human behavior and natural lightning-caused fire can have on an ecosystem’s vegetation, which in turn can give rise to greater, or lesser, frequency of wildfire. The calculations in the computer simulations take those patterns and randomly impose different scenarios into the data to showcase a possible result if such conditions were to happen in the future.
“This is the place where everything that PIRE is doing starts to get really interesting,” said Yospin, who has been working to build the model for Cradle Mountain. “People sometimes jump to the conclusion that using ecological data in a simulation like this will tell them what’s going to happen next year, what forest is going to burn and how much. That is fundamentally unknowable.”
He said that what scientists can do is project vegetation changes under different scenarios of climate that have a lot to do with fire behavior and how we might prepare for and react to those future fires.
Yospin said the model he has been building for Tasmania plots a daily increment of fire conditions over a thousand years, building projections for 5,000 locations. For each set of circumstances it is given, the model will run 250 simulations, yielding millions of data points that will show how climate change will affect everything from the fire frequency to post-fire vegetation recovery.
“The hardest part of what I’m doing is turning (the model results) into something that people can see and understand,” Yospin said. “Imagine that you could hover in a helicopter over Cradle Mountain or Yellowstone for 1,000 years and had a video camera and could document how the landscape changed, day after day. That would be one simulation.”
Whitlock said WildFIRE PIRE’s simulations should serve as a guide for how to incorporate knowledge of past, present and future wildfires into sound forest management and conservation practices, both around the world and in the Greater Yellowstone. With climate models predicting warmer temperatures, Whitlock said global-scale research into the causes and consequences of wildfire has never been more relevant.
“Fires are an ecological concern, but they are also a question of human health and safety—the increase in wildfires from the tropics to the Arctic has become a really big issue—and we think it is one of the most important areas of climate change research that needs attention,” Whitlock said. “And I take a lot of pride that MSU’s reputation as an international research institution has given us a leading role in tackling an environmental challenge that has huge implications for our state, as well as globally.” ■
To learn more about WildFIRE PIRE, see MSU film professor Dennis Aig's podcasts.