Trees are often viewed as a climate solution, because a single tree can suck more than 48 pounds of carbon dioxide out of the atmosphere in a year, according to the U.S. Department of Agriculture. But research now shows logging pollutes more than previously thought.
A study published this month in the journal Nature shows that, even when the carbon captured by trees is factored in, wood harvesting produces about 10% of the world’s greenhouse gas emissions annually.
“This idea that somehow wood is free to use [because there’s no carbon impact], that's just wrong. …” said Timothy Searchinger, the technical director for agriculture, forestry and ecosystems at the World Resources Institute and a co-author on the report. “You can't say they don't have any cost because other forests are growing.”
Forests – especially younger trees – can grow back quickly and take lots of carbon dioxide out of the atmosphere. But harvesting is even quicker, so trees don’t have enough time to catch up. Searchinger said many papers “ignore or hide” that fact and instead say it all balances out.
“They make a kind of a math error,” he said. “They say, ‘So long as the amount of wood you harvest in the country isn’t more than the amount that your forests grow each year, then we're going to say harvesting wood and burning it and otherwise putting carbon into the atmosphere doesn't count, it doesn't increase warming.’”
But the demand for wood is not slowing down. From 2010 to 2050, the study estimates a 54% increase in demand. That would generate more than 4 billion tons of carbon dioxide pollution annually – about the amount generated by “land-use change due to agricultural expansion,” according to the report.
Searchinger added that a lot of harvested wood does not get made into desks or furniture – it just gets burned, which contributes the most to these emissions.
“If we can harvest wood more efficiently, use more of that wood for purposes other than just burning it, we can actually make a big difference,” he said.
He added the solution is not to stop all wood harvesting, but rather to control the growth in demand and give the forests some time to regenerate. He encouraged recycling wood for other purposes and using technology that logs wood more efficiently.
“If you grew back and stopped harvesting the [trees], they would grow back and you get all the carbon back,” he said. But for decades we've increased warming and we can't afford to increase warming in the next several decades. Just look at what's happening today. What we need to be doing is the opposite.”
Searchinger also said people should not be touting wood as good for the climate. He said the annual Interior appropriations bill has a small section that declares forest bioenergy as “carbon neutral.” He called for stronger climate policies that reflect research by him and others.
“This annual provision, which is completely contrary to science, will actually encourage the burning of more wood,” he said. “People need to be aware of [and] stop pretending, declaring contrary to any physical reality, that harvesting and burning wood somehow doesn't add carbon to the atmosphere. It does.”
This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNR in Nevada, KUNC in Colorado and KANW in New Mexico, with support from affiliate stations across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting.
