Scientists have long known that browsing by large animals such as moose, which consume a high number of plants that would otherwise act as carbon sinks, could be an overlooked source of carbon emissions. Now, a team of researchers led by the Norwegian University of Science and Technology (NTNU) has found that moose can greatly reduce carbon storage in clearcut sites. This reduction in sequestered carbon is equivalent to as much as 60 percent of the annual fossil fuel carbon emissions from a region.
“Moose are an ecosystem engineer in the forest ecosystem, and strongly impact everything from the species composition and nutrient availability in the forest,” said study co-author Gunnar Austrheim, an ecologist at NTNU. “A grown animal can eat 50 kilograms of biomass each day during summer.”
Since moose prefer to eat young deciduous trees such as birch, rowan, and willow, the young saplings that would usually sprout in a forest after a timber company clearcuts an area never get the change to grow and thus bind up CO2 in their trunks, leaves, and roots at maturity. “It was really a surprise to see how much moose can influence vegetation growth, the carbon cycle, and the climate system,” said co-author Xiangping Hu, a researcher at the Industrial Ecology Program (IndEcol) at NTNU.
“One of the biggest unknowns that we have in our understanding of the climate system and the carbon cycle is potentially the effect of larger animals, and how they interact with carbon storage in vegetation,” added co-author Francesco Cherubini, the director of IndEcol.
“This study gave us a great opportunity to quantify this effect. We have some numbers that we can relate to the regional carbon budget, and which actually show the importance of large animals like the moose.”
Although previous research has found that moose can be of help to the forest industry – since, by thinning out the deciduous trees they reduce the competition to species preferred by the industry, such as pines or spruce – the current findings suggest that these animals may negatively impact biodiversity and the climate. However, the researchers hope to find a right balance between moose numbers and how forested lands are managed in order to limit excess carbon emissions, boost biodiversity, and increase forest productivity.
“I think as we get more of an understanding of how all these different things are interrelated, land managers could come up with an optimal plan. That could be a much needed win-win solution for climate, for biodiversity, and for timber value,” Cherubini concluded.
The study is published in Journal of Geophysical Research: Biogeosciences.
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