A new report from the University of Alberta stemming from a three-year study into the benefits of retaining woodlands around agricultural operations has found a stark reduction in nitrous oxide emissions while storing up to three times as much carbon.
Cole Gross, research project lead, said aside from environmental benefits, there could be a financial positive to retaining carbon as producer organizations look to become part of a carbon credit system.
“The amount of carbon that the woodland component of these systems hold is much more than the neighbouring crops,” said Gross, a post-doctoral researcher at Yale University’s School of the Environment, who conducted the study while completing his PhD at U of A.
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In addition to carbon storage, Gross said nitrous oxide emissions were reduced by nearly 90 percent compared to fields without woodlands along the margins.
That reduction is tied to less fertilizer use due to wooded areas on those fields as well as the deep roots of woodlands being able to absorb nutrients that might otherwise be lost.
“It keeps the nitrogen cycling internally within that field and eco-system,” he said.
Dead fall also provides benefits, Gross said.
“Nobody has actually looked at the dead wood component in these woodlands’ neighbouring crop fields before. We really wanted to be as comprehensive as possible to say how much carbon are these farmers and landowners retaining on their land.”
Gross said not only does dead wood store a lot of carbon but it affects carbon cycling that potentially allows soil itself to store more.
“We were really able to see the differences between the shelterbelts of the woodland and the hedgerow of the woodlands,” said Gross.
Hedgerows contained more deadfall than the shelterbelts as the latter often include introduced species that might not propagate enough to produce fall trees.
“The hedgerows, because they are naturally occurring and they’ve been there for a long time, so you have this build up of deadwood over time,” he said.
But just planting trees won’t necessarily result in immediate carbon retention, said Gross, pointing out the best benefits come from already existing woodlands.
Conversely, older stands could see all the benefits lost.
“We’re really emphasizing retaining what you have. Retain the woodlands and deadwood and let it lie — don’t take it away unless there are operational needs to do so,” he said.
Gross said there is no immediate financial benefit for farms to do what they can to retain carbon emissions but that is likely to change.
“Hopefully, retaining that carbon can be monetized. If not now, in the very near future,” Gross said. “And there are certainly other benefits to letting the trees be there. Now is not the time to be cutting down additional trees to try to get a little bit of extra planting.”
