A new study that measures the impact of deforestation in New England comes to a conclusion familiar to environmentalists: Forest conservation is a key strategy in addressing climate change.
Deforestation impacts carbon pollution in two ways. Trees soak up carbon dioxide, a greenhouse gas, from the atmosphere, and their disappearance erases that benefit. Then, the act of clearing trees releases some of that stored carbon back into the atmosphere.
Scientists widely agree that carbon dioxide in the atmosphere must remain below 350 parts per million to avoid catastrophic climate change, but in 2021, atmospheric carbon dioxide increased to 420 parts per million, the study released Tuesday says.
Compiled by scientists from Massachusetts-based Clark University and global environmental organization The Nature Conservancy, the report estimates potential emissions that would result from transitioning todays’ forests to developed, agricultural or other non-forested land. It also estimates the actual emissions that resulted from forest clearing in the 1900s and 2000s in all six of New England’s states and New York.
Finally, the study accounts for the lost carbon sequestration during the 1990s and 2000s, as well as the “potential foregone” sequestration that could take place if forests are cleared in the future.
Lead author Christopher Williams, a geography professor at Clark University, used thousands of field plots from the U.S. Forest Service and detailed satellite images to map forest cover and estimate how much carbon the forests held.
Across New England and New York, forest loss is releasing an average of 4.9 million metric tons of carbon dioxide equivalent each year, Williams found. The same states are losing out on an average of 1.2 million metric tons of carbon sequestration per year.
“This forgone sequestration increases the climate impact by 23% above the carbon emissions alone, and that has been missing from previous studies,” Williams said in a presentation of the study’s findings to members of the media on Tuesday.
The losses are permanent, he said.
“Avoiding forest conversion protects today's forest carbon stocks and tomorrow's carbon uptake and can contribute meaningfully to state level climate policy and action,” he said.
Vermont, however, represents a small amount of the carbon burden. The study estimates that deforestation in Vermont accounts for 200,000 metric tons of carbon dioxide each year, which accounts for both emissions and lost sequestration. The state loses an average of 623 acres of forest per year.
By comparison, forest loss in New Hampshire accounts for 700,000 metric tons of carbon dioxide annually. Connecticut accounts for 500,000 metric tons, Maine accounts for 1.1 million metric tons, Massachusetts accounts for 1.3 million and New York accounts for 2.1 million.
Vermont is second only to Rhode Island, which contributes 150,000 metric tons of carbon dioxide per year, representing an average of 591 acres of lost forest annually.
Vermont’s relatively small population is likely the reason behind the state’s low rate of deforestation, said Laura Marx, a forest ecologist with the Massachusetts chapter of the Nature Conservancy.
Still, she said, deforestation in Vermont contributes to 3% of the state’s fossil fuel emissions.
“I think each state has to kind of look at those numbers and make their own conclusions about, you know, are we OK with that?” she told VTDigger.
In the United States, natural climate solutions like forest preservation “can provide a little over 20% of the greenhouse gas reductions and removals that we need in order to meet our obligations under the Paris climate change agreement,” she said.
The idea isn’t to reduce deforestation to zero, she said. Certain types of land development are necessary. But the analysis gives landowners and policy makers a reference point that could be useful for planning.
So much carbon is stored in forests that, when they’re cut down, the carbon released is “irrecoverable on any meaningful human or climate change timescale,” Marx said during Tuesday’s presentation.
“What I mean by that is, if I take 25 acres of forest and I pave them over, there isn't really any amount of tree planting on another 25 acres, or changes to how I do forestry, that can gain back as much carbon as I just lost by deforesting that 25 acres,” she said.
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