Dr. Lindsey Rustad and her colleagues stood in the middle of a New Hampshire forest rimmed by the White Mountains. The sun had set hours ago, and they were staring up toward the sky, where ice-laden tree limbs creaked in the breeze. The weight of the ice bent the branches, and smaller trees completely hunched over under the enormous weight of the frozen water. The wind wasn’t strong enough to knock the ice off; only warmer temperatures would eventually relieve the trees of their heavy burden.
Ice storms are not uncommon in New Hampshire, where Rustad works as team leader for the USDA Forest Service Hubbard Brook Experimental Forest. However, this storm was different: Rustad and her team had just created the world’s first artificial ice storm.
“Ice storms,” Rustad explains in an email, “also known as ‘glazing events,’ are powerful winter weather events common to temperate and boreal forest regions worldwide.” They are caused when air higher up in the atmosphere is warm, but the ground air is sub-freezing. “Precipitation falling as rain from the warmer upper air layer super cools—but does not freeze—as it falls through the cold air, and then freezes on contact as it lands on cold objects such as tree branches, roads, or power lines.”
The resulting layer of ice can cause extreme damage, not only to forest ecosystems but also to roads, power lines, and homes, costing billions of dollars. Rustad lived through the 1998 ice storm, “which crippled much of southeastern Canada and the northeastern U.S.,” she says. “[It] severely damaged forests, paralyzed power grids, left millions without power, cost over $2.2 billion, and caused 44 fatalities.”
For forests, the effects can be devastating. “Large ice storms have catastrophic short-term impacts due to branch breakage and toppling of trees under heavy ice loads,” Rustad tells me. If they become more severe or more frequent due to climate change, “all bets are off. We may see a loss of keystone species.” For example, birch trees may be more susceptible to ice than maple trees. If there are more ice storms, there could be a shift in forest species composition. The effects could go even further, with forests both toppled and changed over to a different state, such as a fern glade—at least for a few decades.
These effects are ominous not only because of their magnitude, but also because they are largely unknown. No detailed long-term research studies had yet been done on ice storms, and none had measured the forest traits before an ice storm hit, because the weather events are difficult to predict. Until now.
Hubbard Brook is part of the Long Term Ecological Research Network, and it has been a site for large-scale research projects for decades. It was established in 1955 by the U.S. Forest Service to study water and watersheds; over time its team of scientists has been credited with discovering acid rain, and initiated research projects on the response of forests to harvests, resident and migratory birds, soil warming, drought, and much more. If there was a place to stage an artificial ice storm, Hubbard Brook was it.
With a $1.4 million grant from the National Science Foundation, Rustad and her team set to work. They took detailed measurements of the forest, including the heights of trees and shrubs, tree health, and biogeochemical cycles. Armed with this baseline data, they were ready to initiate the ice storm.
Unfortunately, an El Niño year limited the days it was actually cold enough to create an ice storm. If the temperature is too high, the water drips off the trees and does not freeze. Finally, on January 18, 2016, everything was aligned.
While the logistics are complicated, the mechanism for creating the ice storm is actually quite simple. The group of researchers rigged up giant hoses—similar to fire hoses—and arched them toward the trees. “We shoot the water up through gaps in the canopy, careful not to hit branches and twigs on the way up,” Rustad explains. “The cold water gets even colder as it goes up through the sub-freezing air, and comes down as a fine mist on the trees, where it freezes on contact.” They sprayed during the day and into the night, when large spotlights allowed them to see their work.
Rustad reflects that the entire experience was “truly amazing… a combination of excitement that it was working, awe at the beauty of the accumulating ice on the branches, and raw fear when branches started cracking, breaking, and crashing down. Everyone was looking up and everyone spontaneously cheered when a branch came down. We were a unified group with a mission and we were all doing our jobs and working well together. It is important to note that everyone was outside the plots by at least 15 feet and the icing was contained inside the plots, so no one was in danger of being hit by falling branches.”
Within hours, tree branches began to bend and snap, falling to earth in explosions of sound as they hit the snow covering the forest floor. The scientists set to work collecting data immediately, and will continue to do so for the next several years.
“This experiment will give us the first-ever detailed cause-and-effect information on how different levels of ice loads affect the biology, chemistry, and biodiversity of northern hardwood forests,” Rustad concludes. “By making all these measurements both before the icing and in control, un-iced plots, and then again after the experimental icing, we will know how all these aspects of forest health and productivity are impacted by the experimental ice storm.”
Long-term studies like the one undertaken by Rustad and her team are becoming ever more important as scientists try to predict the ramifications of climate change. It is their hope that their research “will allow foresters, land managers, and the concerned public to be more knowledgeable about ice storms and their impacts, and able to be more proactive in response to ice storms.”
Erika Zambello is a writer, birder, and photographer living and working along the Emerald Coast of Florida. She has a master’s degree in environmental management from Duke University, specializing in ecosystem science and conservation. Her love of the outdoors was inspired by a childhood in Maine, and she returned for her National Geographic Young Explorer grant in 2015-2016. She currently works as the Marine Economic and Tourist Resource Development Coordinator for Okaloosa County, where she manages ecotourism projects. Erika believes in the power of communicating conservation, and she has written for BirdWatching Daily, 10000birds.com, the Conservation Fund, Triangle Land Conservancy, the Maine Sportsman, the Bangor Daily News, and more. Her passion for exploration was the inspiration for founding both One World, Two Feet and TerraComm. Follow her adventures on Instagram at @a_day_in_the_landscape, and her 30 day challenges here.