Research: Emissions are higher from alpine tundra
By Charlie Brennan
John Knowles took a break Friday from his field work in the Sonoran Desert to talk about some disturbing findings concerning what is happening in the mountains west of Boulder — and, likely, in other similar environments.
Knowles is the lead author on a newly published study that shows that thawing permafrost found in high-altitude mountain ecosystems might be an underexplored contributor to atmospheric carbon dioxide emissions.
Now a postdoctoral researcher in ecosystem science at the University of Arizona, Knowles’ research into carbon dioxide emissions in alpine environments, which spanned more than 10 years, was completed when he was a doctoral student in the University of Colorado’s Department of Geography and a researcher at the Institute of Arctic and Alpine Research. He left Boulder for Arizona in September 2017. “I’d say the most important takeaway from our findings is this is the first work to suggest a mountain analogue to the well-established Arctic tundra permafrost feedback to climate change,” Knowles said.
What Knowles is referring to is research in recent decades that has shown that in the Arctic regions, melting permafrost is now unearthing long-frozen tundra soil and releasing CO2 reserves that had been trapped and buried for centuries.
Knowles and his colleagues collected data at Niwot Ridge Long Term Ecological Research site in Boulder County’s Indian Peaks Wilderness across seven years, 2008 through 2014, gathering samples of soil CO2, then used radiocarbon dating to estimate how long the carbon forming that CO2 had been in the landscape.
Results showed, to the researchers’ surprise, that wind-scoured tundra landscapes above 11,000 feet emitted more CO2 than they captured each year, and that some of that CO2 released in the winter was relatively old, the first such finding of its kind in temperate latitudes.
“During the three-month growing season, when the plants were active, there was some CO2 removed from the atmosphere by plants and brought into tundra,” Knowles said.
“But through the whole rest of the year, the other nine months, the tundra lost that CO2 through the microbes breathing it back out, about six times more, back into the atmosphere. When you add it all up, this ecosystem was persistently emitting CO2 into the atmosphere.”
It is not good news, he said, that although mountains are generally viewed as carbon sinks, places where carbon accumulates and is effectively stored for long periods of time, their tundra regions — and particularly their permafrost-ed areas — may counter that dynamic.
“This is a mechanism, a previously unaccounted for mechanism, by which we could be getting more CO2 into the atmosphere. And we all know what that means,” Knowles said.