Loranty Finds That More Trees Don’t Always Lower Carbon Levels… So What About the Patagonia Sur Pact?


Sophie Boyd, Maroon-News Staff

Assistant Professor of Geography Michael Loranty presented his research on the ecosystemic impact of wildfires and associated climate feedbacks in Siberian boreal forests to students and professors on Thursday, February 15.

Loranty works on the intersection of atmospheric science, ecology and geography. Fittingly, his research studies the interaction of terrestrial ecosystems with the atmosphere, focusing specifically on forest fire regimes in Siberian boreal forests.

Loranty discussed a disturbing trend within North American boreal forests over the past several decades; fire regimes have been intensifying and the burn areas have been doubling each year. In seeking an explanation for this trend, researchers within the last decade have discovered forest recovery after a fire disturbance is changing. Both the type of trees that grow back and the length of time with which these varieties persist have changed as fires become more intense.

Loranty pointed to increased biomass and decreased albedo as two major demographic results of the increasing prevalence of these deciduous trees in boreal forests. These changes have profound implications on the climate. Biomass accumulation from deciduous trees increases the levels of carbon that are taken out of the atmosphere and stored on the terrain, while augmented absorption elevates atmospheric temperature.

Unlike North American boreal forests, little is known about the effects of fire regimes in Siberian boreal forests due to lack of funding, documentation and environmental organizations.

Loranty and his colleagues seek to understand how fire severity influences post-fire regrowth of Siberian boreal forests and the associated climate feedback implications.

Among other issues, Loranty and his colleagues investigated patterns of carbon accumulation across different stands of recovering forests. Here, they observed high variabilities in forest density – directly related to the high volume of carbon accumulation in the vegetation of these areas – and in biomass among different forests in their third decade after fire. Loranty noted that the recovery patterns of these forests did not follow those of typical forest regrowth, leading him to pose another question: Does fire severity influence post-fire stand density?

To answer this, Loranty and his team set small fires of different intensities and tracked seed germination over the course of five years within each region burned. They found that the more severe the fire, the more seedlings germinated in this area. Loranty posited these areas of greater seedling germination will eventually develop into more dense forests.

Wondering if these results would be found in late-successional stands, Loranty examined one forest 50 years post-fire, looking for similar variability in density within a single fire scar. He found that even 50 years later, this forest had similar variability in stand density.

Armed with research showing that Siberian fire intensity affects forest density in ways similar to those of United States boreal forests, Loranty then addressed the climate feedback implications of this varying stand density.

Loranty found that low density stands reflected 60 percent of incoming sunlight, as opposed to high density stands, in which only 25 to 30 percent of sunlight was reflected. Loranty concluded that this high density area will have the effect of heating up the surrounding atmosphere. 

Loranty explained that, as fires become more intense following the trend of the past several decades, fire recovery in these Siberian boreal forests will yield increased tree density and variability, and larger biomass accumulation, which will in turn affect carbon levels in vegetation and atmospheric temperatures.

His research makes it clear increased tree populations may not necessarily lead to lower carbon levels, raising the question of whether or not Colgate’s Patagonia Sur pact to plant 225,000 trees in Chile’s Aysén Region of Patagonia will actually reduce carbon levels.

Sophomore Nick Quinn reflected on how he will implement the research presented to him.

“Now that I know how afforestation can reduce albedo and cause Earth to absorb more heat, I will be able to think more critically when weighing the pros and cons of planting trees,” Quinn said. 

Senior Damis Yancopoulos agreed that Loranty’s research can affect the way he approaches environmental issues. 

“It is pretty interesting that the majority of people have this idea that just planting as many trees as possible, to cycle carbon from the atmosphere, is a foolproof method of combating climate change. Loranty’s research shows that in the high latitudes this actually has the opposite effect,” Yancopoulos said. 

Contact Sophie Boyd at [email protected]